Community hub
0 subscribers8 pages, 0 posts
Recent from talks
All channels
Be the first to start a discussion here.
Be the first to start a discussion here.
Be the first to start a discussion here.
Be the first to start a discussion here.
Contribute something
Welcome to the community hub built to collect knowledge and have discussions related to Animal feed.
Nothing was collected or created yet.
Animal feed
View on Wikipediafrom Wikipedia
 | This article needs additional citations for verification. (February 2024) |
Animal feed is food given to domestic animals, especially livestock, in the course of animal husbandry. There are two basic types: fodder and forage. Used alone, the word feed more often refers to fodder. Animal feed is an important input to animal agriculture, and is frequently the main cost of the raising or keeping of animals. Farms typically try to reduce cost for this food, by growing their own, grazing animals, or supplementing expensive feeds with substitutes, such as food waste like spent grain from beer brewing.
Animal wellbeing is highly dependent on feed that reflects a well balanced nutrition. Some modern agricultural practices, such as fattening cows on grains or in feed lots, have detrimental effects on the environment and animals. For example, increased corn or other grain in feed for cows, makes their microbiomes more acidic weakening their immune systems and making cows a more likely vector for E. coli,[1] while other feeding practices can improve animal impacts. For example, feeding cows certain kinds of seaweed, reduces their production of methane, reducing the greenhouse gases from meat production.[2]
When an environmental crisis strikes farmers or herders, such as a drought or extreme weather driven by climate change, farmers often have to shift to more expensive manufactured animal feed, which can negatively effect their economic viability. For example, a 2017 drought in Senegal reduced the availability of grazing lands leading to skyrocketing demand and prices for manufactured animal feed, causing farmers to sell large portions of their herds.[3] Additionally agriculture for producing animal feed puts pressure on land use: feed crops need land that otherwise might be used for human food and can be one of the driving factors for deforestation, soil degradation and climate change.[4]
Fodder
[edit]
"Fodder" refers particularly to foods or forages given to the animals (including plants cut and carried to them), rather than that which they forage for themselves. It includes hay, straw, silage, compressed and pelleted feeds, oils and mixed rations, and sprouted grains and legumes. Grass and crop residues are the most important source of animal feed globally.[6][7] Grains account for 11% of the total dry matter consume by livestock at global level and oilseed crops by-products such as soybean cakes account for 5%.[6][7] The amount of grain used to produce the same unit of meat varies substantially between species and production systems.[6][7] According to FAO, ruminants require an average of 2.8 kg of grains to produce 1 kg of meat while monogastrics require 3.2.[6][7] These figures vary between 0.1 for extensive ruminant systems to 9.4 in beef feedlots, and from 0.1 in backyard chicken production to 4 in industrial pig production.[6][7] Farmed fish can also be fed on grain and use even less than poultry. The two most important feed grains are maize and soybean, and the United States is by far the largest exporter of both, averaging about half of the global maize trade and 40% of the global soya trade in the years leading up the 2012 drought.[8] Other feed grains include wheat, oats, barley, and rice, among many others.
Traditional sources of animal feed include household food scraps and the byproducts of food processing industries such as milling and brewing. Material remaining from milling oil crops like peanuts, soy, and corn are important sources of fodder. Scraps fed to pigs are called slop, and those fed to chicken are called chicken scratch. Brewer's spent grain is a byproduct of beer making that is widely used as animal feed.
Compound feed is fodder that is blended from various raw materials and additives. These blends are formulated according to the specific requirements of the target animal. They are manufactured by feed compounders as meal type, pellets or crumbles. The main ingredients used in commercially prepared feed are the feed grains, which include corn, soybeans, sorghum, oats, and barley.
Compound feed may also include premixes, which may also be sold separately. Premixes are composed of microingredients such as vitamins, minerals, chemical preservatives, antibiotics, fermentation products, and other ingredients that are purchased from premix companies, usually in sacked form, for blending into commercial rations. Because of the availability of these products, farmers who use their own grain can formulate their own rations and be assured that their animals are getting the recommended levels of minerals and vitamins,[9] although they are still subject to the Veterinary Feed Directive.
According to the American Feed Industry Association, as much as $20 billion worth of feed ingredients are purchased each year. These products range from grain mixes to orange rinds and beet pulps. The feed industry is one of the most competitive businesses in the agricultural sector and is by far the largest purchaser of U.S. corn, feed grains, and soybean meal. Tens of thousands of farmers with feed mills on their own farms are able to compete with huge conglomerates with national distribution. Feed crops generated $23.2 billion in cash receipts on U.S. farms in 2001. At the same time, farmers spent a total of $24.5 billion on feed that year.
With progressing climate change and reoccurring droughts, extensive rangeland agriculture increasingly suffers of forage shortage. Innovative approaches to substitute forage include the harvesting and processing of shrubs into animal feed. This has been extensively researched and applied in Namibia, using waste biomass resulting from woody encroachment.[10]
In 2011, around 734.5 million tons of feed were produced annually around the world.[11]
History
[edit]
The US Animal Drug Availability Act 1996, passed during the Clinton era, was the first attempt in that country to regulate the use of medicated feed.[citation needed]
In 1997, in response to outbreaks of Bovine spongiform encephalopathy, commonly known as mad cow disease, the United States and Canada banned a range of animal tissues from cattle feed. Feed bans in United States (2009) Canada (2007) expanded on this, prohibiting the use of potentially infectious tissue in all animal and pet food and fertilizers.[12]
Forage
[edit]
Forage is a plant material (mainly plant leaves and stems) eaten by grazing livestock.[13] Historically, the term forage has meant only plants eaten by the animals directly as pasture, crop residue, or immature cereal crops, but it is also used more loosely to include similar plants cut for fodder and carried to the animals, especially as hay or silage.[14]
While the term forage has a broad definition, the term forage crop is used to define crops, annual or biennial, which are grown to be utilized by grazing or harvesting as a whole crop.[15]Manufacture
[edit]Feed manufacturing refers to the process of producing animal feed from raw agricultural products. Fodder produced by manufacturing is formulated to meet specific animal nutrition requirements for different species of animals at different life stages. According to the American Feed Industry Association (AFIA),[16] there are four basic steps:
- Receive raw ingredients: Feed mills receive raw ingredients from suppliers. Upon arrival, the ingredients are weighed, tested and analyzed for various nutrients and to ensure their quality and safety.
- Create a formula: Nutritionists work side by side with scientists to formulate nutritionally sound and balanced diets for livestock, poultry, aquaculture and pets. This is a complex process, as every species has different nutritional requirements.
- Mix ingredients: Once the formula is determined, the mill mixes the ingredients to create a finished product.
- Package and label: Manufacturers determine the best way to ship the product. If it is prepared for retail, it will be "bagged and tagged," or placed into a bag with a label that includes the product's purpose, ingredients and instructions. If the product is prepared for commercial use, it will be shipped in bulk.
Nutrition
[edit]In agriculture today, the nutritional needs of farm animals are well understood and may be satisfied through natural forage and fodder alone, or augmented by direct supplementation of nutrients in concentrated, controlled form. The nutritional quality of feed is influenced not only by the nutrient content, but also by many other factors such as feed presentation, hygiene, digestibility, and effect on intestinal health.[17]
Feed additives provide a mechanism through which these nutrient deficiencies can be resolved, improving animal rate of growth, health, and well-being. Many farm animals have a diet largely consisting of grain-based ingredients because of the higher costs of quality feed.[17][18]
Major ingredients
[edit]Chelates
[edit]6_cation.png)
Chelates in animal feed is jargon for metalloorganic compounds added to animal feed. The compounds provide sources of various metals that improve the health or marketability of the animal. Typical metal salts are derived from cobalt, copper, iron, manganese, and zinc. The objective of supplementation with trace minerals is to avoid a variety of deficiency diseases. Trace minerals carry out key functions in relation to many metabolic processes, most notably as cofactors for enzymes and hormones, and are essential for optimum health, growth and productivity. For example, supplementary minerals help ensure good growth, bone development, feathering in birds, hoof, skin and hair quality in mammals, enzyme structure and functions, and appetite. Deficiency of trace minerals affects many metabolic processes and so may be manifested by different symptoms, such as poor growth and appetite, reproductive failures, impaired immune responses, and general ill-thrift. From the 1950s to the 1990s most trace mineral supplementation of animal diets was in the form of inorganic minerals, and these largely eradicated associated deficiency diseases in farm animals. The role in fertility and reproductive diseases of dairy cattle highlights that organic forms of Zn are retained better than inorganic sources and so may provide greater benefit in disease prevention, notably mastitis and lameness.
Animals are thought to better absorb, digest, and use mineral chelates than inorganic minerals or simple salts.[19] In theory lower concentrations of these minerals can be used in animal feeds. In addition, animals fed chelated sources of essential trace minerals excrete lower amounts in their faeces, and so there is less environmental contamination.Insects
[edit]
Insects as feed are insect species used as animal feed, either for livestock, including aquaculture, or as pet food.
As livestock feed production uses ~33% of the world's agricultural cropland use, insects might be able to supplement livestock feed. They can transform low-value organic wastes, are nutritious and have low environmental impacts.[20]Soy
[edit].jpg)
By animal
[edit]See also
[edit]References
[edit]- ^ "The Bio-Hazard of Corn Fed Beef". Mother Earth News. 2006-12-01. Retrieved 2020-11-27.
- ^ "Seaweed-fed cows could solve livestock industry's methane problems". www.abc.net.au. 2017-04-21. Retrieved 2020-11-27.
- ^ "How climate change is plunging Senegal's herders into poverty". The New Humanitarian. 2018-10-10. Retrieved 2020-11-26.
- ^ Rojas-Downing, M. Melissa; Nejadhashemi, A. Pouyan; Harrigan, Timothy; Woznicki, Sean A. (2017-01-01). "Climate change and livestock: Impacts, adaptation, and mitigation". Climate Risk Management. 16: 145–163. doi:10.1016/j.crm.2017.02.001. ISSN 2212-0963.
- ^ "Horse Nutrition - Feeding factors". Bulletin 762-00, Ohio State University. Accessed February 9, 2007.
- ^ a b c d e Mottet, A.; de Haan, C.; Falcucci, A.; Tempio, G.; Opio, C.; Gerber, P. (2022). More fuel for the food/feed debate. Rome: FAO.
- ^ a b c d e Mottet, Anne; de Haan, Cees; Falcucci, Alessandra; Tempio, Giuseppe; Opio, Carolyn; Gerber, Pierre (2017-09-01). "Livestock: On our plates or eating at our table? A new analysis of the feed/food debate". Global Food Security. Food Security Governance in Latin America. 14: 1–8. doi:10.1016/j.gfs.2017.01.001. ISSN 2211-9124.
- ^ J. P. (2 August 2012). "Is soya next?". The Economist. Retrieved 2022-07-23.
- ^ R. A. Zinn, A Guide to Feed Mixing, University of California, Davis.
- ^ Mupangwa, Johnfisher; Lutaaya, Emmanuel; Shipandeni, Maria Ndakula Tautiko; Kahumba, Absalom; Charamba, Vonai; Shiningavamwe, Katrina Lugambo (2023), Fanadzo, Morris; Dunjana, Nothando; Mupambwa, Hupenyu Allan; Dube, Ernest (eds.), "Utilising Encroacher Bush in Animal Feeding", Towards Sustainable Food Production in Africa: Best Management Practices and Technologies, Sustainability Sciences in Asia and Africa, Singapore: Springer Nature, pp. 239–265, doi:10.1007/978-981-99-2427-1_14, ISBN 978-981-99-2427-1, retrieved 2023-10-13
- ^ Peter Best, "World Feed Panorama: Once again, industry increases its volume", Feed Strategy, 31-01-2012.
- ^ "Feed Bans BSE (Bovine Spongiform Encephalopathy) | Prion Diseases | CDC". www.cdc.gov. Retrieved 2016-09-30.
- ^ Fageria, N.K. (1997). Growth and Mineral Nutrition of Field Crops. NY, NY: Marcel Dekker. p. 595.
- ^ Fageria, N.K. (1997). Growth and Mineral Nutrition of Field Crops. NY, NY: Marcel Dekker. p. 583.
- ^ Givens, D. Ian (2000). Forage evaluation in ruminant nutrition. CABI. p. 1. ISBN 978-0-85199-344-7.
- ^ "How Feed is Made – AFIA". www.afia.org. Retrieved 2021-08-18.
- ^ a b Merck Manual October 2014, Nutritional Requirements of Beef Cattle, Accessed March 18, 2015.
- ^ Merck Manual March 2012, Requirements of Beef Cattle, Accessed March 18, 2015.
- ^ Richards, James D.; Fisher, Paula M.; Evans, Joseph L.; Wedekind, Karen J. (2015-06-25). "Greater bioavailability of chelated compared with inorganic zinc in broiler chicks in the presence or absence of elevated calcium and phosphorus". Open Access Animal Physiology. 7: 97–110. doi:10.2147/OAAP.S83845. Retrieved 2019-12-20.
- ^ van Huis, Arnold; Gasco, Laura (13 January 2023). "Insects as feed for livestock production". Science. 379 (6628): 138–139. Bibcode:2023Sci...379..138V. doi:10.1126/science.adc9165. ISSN 0036-8075. PMID 36634163. S2CID 255749691.
- News report on the study: Yirka, Bob. "Making the case for using insects as food for both humans and livestock". phys.org. Archived from the original on 28 January 2023. Retrieved 17 February 2023.
- ^ Purcell, Larry C.; Salmeron, Montserrat; Ashlock, Lanny (2000). "Chapter 19: Soybean Facts". Arkansas Soybean Production Handbook - MP197. Little Rock, AR: University of Arkansas Cooperative Extension Service. p. 1. Archived from the original (PDF) on 4 March 2016. Retrieved 2 March 2016.
- ^ Cheng, Ming-Hsun; Rosentrater, Kurt A. (2019). "Techno-Economic Analysis of Extruding-Expelling of Soybeans to Produce Oil and Meal". Agriculture. 9 (5): 87. doi:10.3390/agriculture9050087. ISSN 2077-0472.
- ^ Stein, H. H., L. L. Berger, J. K. Drackley, G. C. Fahey Jr, D. C. Hernot and C. M. Parsons. 2008. Nutritional properties and feeding values of soybeans and their coproducts. Soybeans chemistry, production, processing, and utilization. AOCS Press, Urbana, IL. pp. 613-660.
- ^ Soybean Feed Industry Guide. 2010. 1st Ed. https://cigi.ca/wp-content/uploads/2011/12/2010-Soybean-Feed-Industry-Guide.pdf Archived 2021-03-08 at the Wayback Machine
External links
[edit]
Look up animal feed in Wiktionary, the free dictionary.
Animal feed
View on Grokipediafrom Grokipedia
Types and Classification
Forage and Pasture-Based Feeds
Forage encompasses plants or plant parts, excluding separated grains, that are consumed by grazing animals either fresh, dried as hay, or preserved as silage.[9] Pasture-based feeds consist of managed grasslands or leys where livestock graze directly on living vegetation, primarily grasses and legumes.[10] These feeds form the foundational diet for ruminants such as cattle, sheep, and goats, providing essential fiber for rumen fermentation while supporting microbial digestion of structural carbohydrates.[11] Common forage types include cool-season grasses like perennial ryegrass and orchardgrass, warm-season varieties such as bermudagrass, and legumes including alfalfa, white clover, and birdsfoot trefoil.[12] Legumes enhance nitrogen fixation, reducing reliance on synthetic fertilizers and improving soil fertility in mixed pastures.[13] Harvested forages like hay or silage extend usability beyond grazing seasons, with preservation methods minimizing nutrient loss; for instance, ensiling ferments sugars into acids to inhibit spoilage.[14] Nutritionally, high-quality pastures on a dry matter basis typically contain 15-25% crude protein, 30-50% neutral detergent fiber, and sufficient digestible energy from non-structural carbohydrates for maintenance and moderate production in ruminants.[15] However, forage quality declines with plant maturity, as crude protein decreases and fiber content rises, potentially limiting intake and digestibility; young vegetative growth offers higher energy but requires rotational grazing to sustain yields.[10] For optimal rumen function, diets should include at least 20% effective neutral detergent fiber to promote chewing and saliva production, buffering rumen pH.[16] Pasture-based systems offer economic advantages through reduced supplemental feed costs and improved animal welfare via natural foraging behaviors, alongside environmental gains like enhanced biodiversity and carbon sequestration in soils.[17] Rotational grazing in these systems can boost forage production by 20% over continuous stocking, allowing plant recovery and minimizing soil compaction.[18] Limitations include seasonal variability in availability and quality, necessitating supplementary feeding during droughts or winter, and higher labor demands for fencing and herd movement compared to confinement feeding.[19] Overgrazing risks pasture degradation, while parasite loads may increase without strategic management.[20]
Concentrates and Compound Feeds
Concentrates are animal feeds characterized by high energy density and low fiber content, typically containing less than 18% crude fiber on a dry matter basis, which distinguishes them from forages.[4] They provide concentrated sources of carbohydrates, proteins, and fats to supplement basal roughage diets, enabling higher nutrient intake for production animals.[21] Common ingredients include cereal grains such as corn, barley, and wheat for energy, and protein-rich materials like soybean meal and cottonseed meal.[9] In ruminant nutrition, concentrates boost total digestible nutrients (TDN), often exceeding 70-80% TDN, compared to forages' lower values, supporting increased milk yield or weight gain when forage alone limits energy.[22] However, excessive concentrate feeding without adequate forage can disrupt rumen fermentation, leading to acidosis, reduced fiber digestion, and higher fat content in meat products.[23][24] Compound feeds, also termed complete or compounded rations, integrate concentrates with minimal forage components, supplements, and additives into a balanced mixture designed to meet specific nutritional requirements as the sole diet.[25] These are processed into forms like pellets, mash, or crumbles to enhance palatability, reduce sorting, and improve digestibility, particularly for monogastrics such as poultry and swine where precise amino acid and energy balances are critical.[22] Formulation relies on least-cost optimization, incorporating ingredients like grains (60-70% of mix), oilseed meals (15-25%), and by-products to achieve targeted crude protein (16-20%) and metabolizable energy levels (e.g., 3,000-3,200 kcal/kg for broiler feeds).[4] Global production of compound feeds reached approximately 1.3 billion metric tons in 2023, rebounding to 1.396 billion metric tons in 2024, driven by demand in poultry (45% of total) and swine sectors amid intensive farming expansion.[26][27] In practice, compound feeds offer advantages in uniform nutrient delivery and efficiency, with studies showing 20:80 forage-to-concentrate ratios improving feed intake, growth rates, and skeletal development in lambs compared to higher forage diets.[24] For dairy cattle, concentrates in compounds elevate energy supply during peak lactation, but ratios must maintain at least 40-50% forage to preserve rumen health and milk fat content.[21] Drawbacks include dependency on imported grains, vulnerability to price volatility, and environmental costs from monocrop sourcing, though by-product inclusion mitigates waste and human-edible competition.[28] Regulatory standards, such as those from the U.S. FDA or EU feed hygiene directives, mandate testing for contaminants like mycotoxins to ensure safety.[4]Supplements and Additives
Supplements and additives comprise non-nutritive or trace-level substances incorporated into animal feeds to compensate for dietary shortfalls, enhance physiological functions, or modify feed properties. Nutritional supplements target essential micronutrients absent or inadequate in base rations, such as vitamins, minerals, and amino acids, while additives encompass functional categories like enzymes, probiotics, and preservatives that influence digestion, microbial balance, or stability. These components are added in minimal quantities—often milligrams per kilogram—to avoid toxicity while achieving targeted outcomes, with formulations tailored to species, production stage, and environmental factors.[29][30] Vitamins constitute a core supplement group, addressing deficiencies in intensive systems where natural synthesis or forage intake is limited. Fat-soluble vitamins A, D, and E support epithelial integrity, calcium-phosphorus metabolism, and oxidative stress resistance, respectively; for example, vitamin D supplementation prevents rickets in housed calves by facilitating intestinal calcium absorption, as basal feeds from grains or silage provide insufficient levels under low sunlight conditions. Water-soluble B vitamins, including riboflavin, niacin, and B12, are routinely added to pig and poultry diets, where microbial synthesis in the gut may not meet demands during rapid growth phases. Empirical trials demonstrate that vitamin E supplementation at 100-200 IU/kg improves immune response and meat quality in finishing pigs by reducing lipid peroxidation.[31][32] Minerals and amino acids form another foundational supplement category, critical for metabolic and structural needs. Macrominerals like calcium (0.3-0.6% of diet) and phosphorus (0.2-0.4%) are supplemented via dicalcium phosphate to balance forage-based rations, preventing hypocalcemia and supporting skeletal development in dairy cows and broilers. Trace minerals such as zinc (50-100 mg/kg), copper (10-20 mg/kg), and selenium (0.1-0.3 mg/kg) enhance enzyme activity and antioxidant defenses; deficiency trials in beef cattle show zinc supplementation increases average daily gain by 0.1-0.2 kg/day through improved rumen function. Essential amino acids, notably lysine (0.9-1.2% for swine) and methionine (0.3-0.5% for poultry), are crystalline-supplemented to synthetic feeds, as cereal grains supply imbalanced profiles; meta-analyses confirm 5-10% feed efficiency gains from precise supplementation, reducing nitrogen excretion.[33][32] Functional additives extend beyond nutrition to optimize utilization and health. Enzymes like phytase (500-1000 FTU/kg) hydrolyze indigestible phytate in plant-based feeds, boosting phosphorus bioavailability by 20-40% and minimizing mineral supplementation needs in pigs and poultry. Probiotics and prebiotics modulate gut microbiota, with strains such as Lactobacillus improving pathogen resistance; controlled studies report 3-5% growth promotion in weaned piglets via enhanced nutrient absorption. Preservatives like propionic acid inhibit mold in silage, preserving energy content, while antioxidants such as ethoxyquin stabilize unsaturated fats against rancidity.[30][34] Antibiotics and growth promoters have historically boosted performance by 5-10% through altered gut ecology but carry risks of resistance transfer to human pathogens, prompting regulatory curbs; the European Union banned sub-therapeutic antibiotics in feed effective January 1, 2006, citing insufficient safety margins despite efficacy data. Alternatives like phytogenics (e.g., essential oils from oregano or cinnamon) exhibit antimicrobial effects without resistance induction, with reviews showing equivalent improvements in feed conversion ratios for broilers. Methane inhibitors, such as 3-nitrooxypropanol at 60-80 mg/kg, reduce enteric emissions by 20-30% in ruminants without compromising milk yield, based on dairy cow trials.[35][34][36] Regulatory frameworks mandate pre-market authorization, emphasizing dose-response efficacy, residue limits, and environmental impact. The European Food Safety Authority assesses additives for target species safety, consumer exposure (e.g., via meat/milk), and worker handling risks, approving only those with net benefits outweighing hazards. In the United States, the FDA oversees via the Federal Food, Drug, and Cosmetic Act, requiring new animal drug applications for novel additives. Global meta-analyses affirm non-antibiotic additives enhance productivity across nine livestock species, with average daily gains up 4-7% and immunity markers elevated, though efficacy varies by baseline diet quality and additive purity. Overuse risks, including toxicity from mineral excess (e.g., copper poisoning in sheep at >25 mg/kg), underscore the need for precise formulation grounded in nutritional modeling.[30][37][38]Historical Development
Ancient and Pre-Industrial Practices
Livestock feeding in ancient times relied predominantly on natural grazing and foraging, coinciding with animal domestication during the Neolithic period around 10,000 BCE in the Fertile Crescent, where sheep, goats, and cattle subsisted on wild grasses and browse without supplemental feeds.[39] In Mesopotamia, barley served as a primary crop for both human rations and animal fodder, with sheep and goats herded on steppe lands supplemented by grain by-products. Egyptian practices from circa 3000 BCE emphasized grazing alongside crop residues, with cattle, sheep, and poultry fed chaff, bran, and occasionally fish meal or milk; forced-feeding using tubes was employed to fatten geese and oxen for slaughter or labor efficiency.[40] In classical antiquity, Roman agronomists like Columella (1st century CE) documented stall-feeding of oxen with hay and legumes during winter, while pigs scavenged acorns and kitchen waste, reflecting integrated mixed farming systems that conserved fodder through mowing meadows.[41] Greek texts from the same era describe similar reliance on pasture grasses, olive leaves, and grape pomace for goats and sheep, prioritizing local vegetation over cultivated feeds to sustain draft animals for plowing and transport.[42] Pre-industrial practices in medieval Europe (circa 500–1800 CE) advanced fodder preservation, with haymaking in summer for winter stall-feeding of cattle and horses, enabling overwintering in barns; turnips and clover rotations, introduced in the 17th century, boosted feed availability and soil fertility in regions like England.[43] In Asia, Chinese pig husbandry from ancient dynasties utilized household scraps, rice bran, and vegetable wastes as feeds, integrating swine into farm cycles for manure production, while steppe nomads in Mongolia practiced dairying with grazing supplemented by stored milk products by 1300 BCE.[44] These methods prioritized seasonal availability and waste recycling, limiting productivity compared to later industrialized systems due to dependence on climatic variability and manual harvesting.[45]Industrialization and Scientific Advances
The industrialization of animal feed production accelerated in the late 19th and early 20th centuries, driven by advancements in transportation, mechanization, and agricultural intensification that enabled the shift from farm-mixed rations to centralized commercial manufacturing. Railroads facilitated the bulk shipment of grains and by-products, allowing mills to process ingredients like wheat bran and corn into standardized feeds, with the first dedicated feed mills emerging in the 1920s as the industry reached billion-dollar scale in the United States. By the 1940s, corn yields surged due to hybrid varieties and fertilizers, while soybean processing expanded, providing high-protein meals essential for compound feeds that supported growing livestock populations in concentrated operations.[46][47] Scientific progress in animal nutrition underpinned these developments, beginning with early feed valuation systems such as Albrecht Daniel Thaer's 1810 hay equivalents, which quantified feed energy relative to hay for rational rationing. The discovery of vitamins in the early 20th century, including vitamin D's role in rickets prevention for poultry (isolated in 1919-1922), led to fortified feeds that addressed deficiencies in intensive systems, improving growth rates and survival. Balanced rations, informed by proximate analysis methods developed in the 1860s by Henneberg and Stohmann, evolved into precise formulations by the 1920s, incorporating empirical data on protein, energy, and mineral needs to optimize feed efficiency.[47][41] Pelleting technology marked a key manufacturing advance, with Purina initiating commercial pelleting of flour mill wastes in 1928 to enhance digestibility and reduce waste in monogastric diets, followed by Wenger's 1946 innovation for high-molasses cattle pellets that improved palatability and nutrient uniformity. Feed additives further revolutionized productivity; urea, synthesized in 1828 but adopted as a non-protein nitrogen source in ruminant feeds by the 1930s, allowed cost-effective protein supplementation, while antibiotics like aureomycin gained FDA approval for growth promotion in 1951, boosting feed conversion by 5-10% in trials through reduced disease incidence. These interventions, grounded in controlled experiments, causal links between gut microbiota and efficiency, and empirical livestock performance data, enabled the scaling of feedlot systems but raised long-term concerns over resistance, as evidenced by post-1950s monitoring.[48][49][50][51]Modern Era and Globalization
The modern era of animal feed, spanning the late 20th century to the present, has been characterized by advancements in feed formulation and manufacturing technologies that enhanced nutritional precision and production efficiency. From the 1970s onward, innovations such as extrusion processing, enzyme supplementation, and computerized diet formulation enabled the optimization of feed conversion ratios in intensive livestock systems, reducing waste and improving animal growth rates.[52][41] These developments supported the expansion of confined feeding operations, particularly in poultry and swine production, where compound feeds now constitute over 90% of diets in major producing regions like North America and Europe.[53] Globalization has transformed the animal feed sector into a highly interconnected industry, with international trade in key ingredients such as soybeans, corn, and fishmeal driving supply chains across continents. By the early 21st century, Brazil emerged as the dominant exporter of soybean meal, supplying over 50% of global trade volumes to meet demand from Asia's rapidly growing livestock sectors, particularly in China, which became the world's largest importer of feed grains.[54][55] This shift was fueled by post-1980s agricultural expansions in South America, where genetically modified crops increased yields, enabling exports that underpinned a tripling of global meat production from 1990 to 2020.[56] The sector's annual turnover exceeds $400 billion, reflecting integrated multinational operations that source ingredients from diverse regions to mitigate local shortages and stabilize prices.[57][26] However, globalization has introduced vulnerabilities, including supply disruptions from geopolitical events and climate variability affecting primary production areas. For instance, the 2022 disruptions in Ukraine's grain exports highlighted dependencies on concentrated sourcing, prompting diversification efforts toward alternative proteins like insect meal in Europe.[58] Environmental analyses indicate that embedded nitrogen emissions in global livestock feed chains have risen disproportionately, with imports accounting for over 40% of consumption in high-income countries.[59] Regulatory harmonization, such as Codex Alimentarius standards, has facilitated trade while addressing safety concerns, though disparities persist between developed and developing markets.[41]Production Processes
Ingredient Sourcing and Supply Chains
The sourcing of ingredients for animal feed primarily relies on agricultural commodities, with corn and soybeans dominating as energy and protein sources, respectively. Corn, the principal feed grain, accounts for over 95% of total feed grain production and use in the United States, the world's largest producer, where it supplies essential carbohydrates for livestock diets.[60] Globally, soybeans are crushed to produce meal, which provides high-quality protein; approximately 70% of soybeans are directed toward animal feed in the form of meal, with major production concentrated in the Americas, including the US, Brazil, and Argentina.[61] These crops form the backbone of feed formulations, comprising 83-91% of ration ingredients by weight in many livestock operations.[62] Supply chains for these ingredients involve multiple stages: cultivation on vast farmlands, harvest and initial storage at grain elevators, transportation via rail, barge, or truck to processing facilities, and final milling into feed. In the US, corn moves from Midwest farms to ethanol plants or direct feed mills, while soybeans undergo crushing to separate oil and meal, with the meal then distributed to compound feed manufacturers.[63] International trade amplifies these chains, as regions like Europe and Asia import significant volumes from the Americas to meet domestic shortfalls, exposing the system to geopolitical risks, weather variability, and logistical bottlenecks.[64] For instance, supply disruptions from events such as droughts or trade policies can induce price volatility, prompting feed producers to diversify sourcing strategies across origins like sorghum or barley when primary supplies falter.[65] Emerging alternatives, including byproducts from food processing and novel proteins like insect meal or algae, are increasingly sourced to enhance resilience and sustainability, though they currently represent a minor fraction compared to staple grains and oilseeds. Sourcing these involves specialized suppliers focusing on non-GMO or organic variants to align with market demands for traceable, lower-impact feeds.[66] Environmental assessments of these chains, as outlined by international guidelines, emphasize tracing from farm to feed to mitigate impacts like deforestation linked to soy expansion in South America, though empirical data underscores the efficiency gains from concentrated production regions.[67] Overall, the global scale—projected to support a market exceeding USD 500 billion by 2030—relies on integrated logistics to ensure consistent quality and affordability, with corn alone topping ingredient usage by weight across species.[68][69]Manufacturing Techniques
Animal feed manufacturing techniques transform raw ingredients into uniform, stable products through sequential mechanical, thermal, and forming processes that enhance digestibility, nutrient bioavailability, and handling efficiency. These methods, scaled for industrial mills processing thousands of tons daily, prioritize particle size reduction, homogenization, and densification to minimize feed waste and support precise nutrition delivery. Core techniques include grinding (or crushing), batching and mixing, conditioning, pelleting or extrusion, cooling, and optional post-treatments like crumbling or coating.[70][71] Grinding reduces ingredient particle sizes using hammer mills, which employ high-speed rotating hammers to shatter materials, or roller mills, which crush via compression between corrugated rollers; target sizes range from 500 to 2,000 microns depending on species, as finer particles improve mixing uniformity and rumen passage rates in cattle while avoiding excessive dust generation. This step increases surface area for microbial fermentation and enzymatic breakdown, boosting nutrient utilization by up to 10-15% in pelleted feeds compared to unprocessed mash.[71][72] Batching precisely weighs ingredients per formulation, followed by mixing in horizontal ribbon or vertical paddle mixers to achieve homogeneity, with coefficients of variation below 5% essential for consistent nutrient delivery across batches. Conditioning then introduces steam and moisture (to 15-18%) in preconditioners, gelatinizing starches and softening fibers to facilitate downstream forming while reducing energy costs in pelleting by improving throughput.[71] Pelleting compresses conditioned mash through a pellet mill's rotating die and rollers at pressures of 20-50 bar and temperatures of 70-90°C, forming dense cylindrical pellets (3-10 mm diameter) that resist breakage, reduce selective feeding, and enhance palatability for ruminants and poultry. Extrusion, an alternative for aquaculture or high-moisture feeds, propels mash through a twin-screw extruder at 100-150°C and shear forces exceeding 100 rpm, expanding the product into porous, floating forms that improve buoyancy and pathogen inactivation via Maillard reactions.[71][72] Post-forming, pellets undergo counterflow cooling to ambient temperature within 10-20 minutes, stabilizing structure and preventing mold via moisture reduction to 10-12%, followed by screening to remove fines and optional crumbling for young animals or oil coating for energy-dense feeds. These techniques, automated in modern facilities with PLC controls, ensure compliance with standards like those from the FDA or AAFCO, though efficacy depends on ingredient quality and mill calibration to avoid overprocessing, which can degrade heat-sensitive vitamins.[70][73]Quality Control and Regulatory Standards
Quality control in animal feed production encompasses systematic testing and monitoring to verify nutritional composition, detect contaminants, and ensure compliance with safety standards. Manufacturers routinely analyze feeds for essential nutrients such as crude protein, fiber, and energy content using methods like near-infrared spectroscopy and wet chemistry, with laboratories adhering to quality management systems recommended by organizations like the Association of American Feed Control Officials (AAFCO).[74] Contaminant testing targets biological hazards including Salmonella spp. and Listeria monocytogenes, chemical residues such as mycotoxins (e.g., aflatoxins limited to 20 ppb in US cattle feeds by FDA action levels), pesticides, heavy metals, and dioxins, often through programs like the FDA's Animal Food Contaminants Monitoring.[75][76] Hazard Analysis and Critical Control Points (HACCP) principles are widely applied, requiring identification of risks like cross-contamination during mixing or storage, establishment of critical limits, and ongoing verification to prevent hazards from entering the feed chain.[77][78] In the United States, the Food and Drug Administration's Center for Veterinary Medicine (FDA CVM) enforces regulations under the Federal Food, Drug, and Cosmetic Act, mandating that feeds be safe, properly labeled, and free from adulterants, with the 2015 Food Safety Modernization Act (FSMA) requiring facilities to implement preventive controls including hazard analysis and risk-based measures.[79] The U.S. Department of Agriculture (USDA) oversees aspects like rendered animal byproducts to prevent diseases such as bovine spongiform encephalopathy, prohibiting mammalian proteins in ruminant feeds since 1997.[80] AAFCO provides model guidelines for ingredient definitions and labeling, adopted by most states, emphasizing truthful representation of feed guarantees.[81] European Union regulations, governed by Regulation (EC) No 767/2009, establish requirements for feed marketing, composition, and labeling, with strict limits on contaminants like ochratoxin A (0.25 mg/kg in complementary feeds) and mandatory hygiene controls under Regulation (EC) No 183/2005, including registration of establishments and traceability.[82][83] The European Food Safety Authority assesses risks, supporting harmonized standards for additives and undesirable substances to protect animal health and the food chain. There are no specific maximum levels for total sulfur in EU animal feed regulations under Directive 2002/32/EC on undesirable substances or its amendments; EFSA evaluates sulfur compounds such as sulfites as additives and sulfates in water, but imposes no binding dietary sulfur caps for feeds, consistent with international scientific consensus including NRC guidelines.[84][85] Internationally, the Codex Alimentarius Commission's Code of Practice on Good Animal Feeding (CAC/RCP 54-2004) outlines a holistic feed safety system covering sourcing, production, and distribution, emphasizing prevention of chemical, physical, and biological hazards through good practices like supplier audits and record-keeping.[86] Voluntary certifications such as GMP+ and FAMI-QS build on these, verifying compliance via audits, though enforcement varies by jurisdiction, with recalls occurring for exceedances like fumonisin levels prompting interventions in 2023 US cases.[87] Non-compliance can lead to economic losses and health risks, underscoring the causal link between rigorous controls and reduced incidence of feed-borne issues like mycotoxicosis in livestock.[88]Nutritional Foundations
Essential Nutrients and Requirements
Animal feeds must supply six classes of essential nutrients—water, carbohydrates, proteins, lipids (fats), vitamins, and minerals—to meet the physiological demands of livestock for maintenance, growth, reproduction, lactation, and work.[89] These nutrients support cellular functions, energy metabolism, structural integrity, and enzymatic reactions, with requirements quantified based on species-specific data from experimental trials and metabolic studies.[90] Deficiencies impair performance, while excesses can cause toxicity or inefficiencies; thus, formulations balance needs against feed composition and animal factors like age, weight, production stage, and environment.[91] The National Research Council (NRC) publishes updated requirement tables derived from peer-reviewed research, emphasizing digestible rather than total nutrient intake to account for bioavailability.[90] Proteins provide amino acids for muscle development, hormone synthesis, and nitrogen balance, with ruminants synthesizing microbial protein from non-protein nitrogen while monogastrics require preformed essential amino acids such as lysine, methionine, threonine, and tryptophan.[5] Requirements range from 10-18% crude protein in dry matter for growing beef cattle to over 20% for lactating sows, adjusted for rumen degradability in cattle or ileal digestibility in pigs.[16][91] Carbohydrates, primarily as starches, fibers, and sugars, serve as the main energy source, fermented to volatile fatty acids in ruminants or digested to glucose in monogastrics, comprising 50-80% of feed energy needs.[92] Lipids supply concentrated energy (2.25 times that of carbohydrates) and essential fatty acids like linoleic acid, required at 0.5-2% of diet for membrane integrity and reproduction, though most animals meet needs via microbial synthesis or feed fats.[89] Vitamins function as coenzymes in metabolism; fat-soluble vitamins (A, D, E, K) accumulate in tissues and require 1-10 IU/kg body weight daily equivalents, while water-soluble B vitamins are often synthesized by gut microbes in ruminants but must be supplemented in young or stressed animals.[89][93] Minerals include macrominerals (calcium at 0.3-0.6% for growing cattle, phosphorus at 0.2-0.4%) for bone formation and electrolyte balance, and trace minerals (zinc 30-40 mg/kg, selenium 0.1-0.3 mg/kg) for enzyme activation and immunity, with interactions like calcium-phosphorus ratios (1.2-2:1) critical to prevent antagonisms.[5][91]| Nutrient Class | Primary Functions | Examples of Requirements (Beef Cattle, NRC Basis) |
|---|---|---|
| Proteins | Tissue repair, enzymes | 11-14% crude protein in diet for maintenance/growth[5] |
| Carbohydrates | Energy via fermentation/digestion | 50-70% of dry matter as neutral detergent fiber/soluble carbs[92] |
| Lipids | Energy density, fatty acids | 2-5% total fat, linoleic acid minimum 0.5% |
| Vitamins | Metabolic cofactors | Vitamin A: 30 IU/kg body weight; E: 15-30 IU/kg feed[93] |
| Minerals | Structural, regulatory | Ca: 0.4%; P: 0.25%; Zn: 30 mg/kg[91] |
| Water | Solvent, thermoregulation | 3-5% body weight daily intake, increasing with dry feed and heat[94] |
Diet Formulation and Efficiency
Diet formulation in animal nutrition involves selecting and proportioning feed ingredients to meet specific nutrient requirements for target species, production stages, and physiological states while minimizing costs and maximizing efficiency.[8] This process relies on established nutrient standards, such as those outlined by the National Research Council, which derive requirements from empirical feeding trials measuring growth, reproduction, and health outcomes.[96] Key steps include defining the animal's needs (e.g., energy as metabolizable energy for monogastrics or net energy for ruminants), compiling ingredient nutrient profiles from laboratory analyses, and applying optimization algorithms to balance macronutrients like carbohydrates for energy, proteins via digestible amino acids (e.g., lysine:calorie ratios of 0.35-0.45 g/Mcal in swine), and minerals such as standardized ileal digestible phosphorus at 0.30-0.40% for broilers.[97] [96] Least-cost formulation, the dominant method since the 1950s, employs linear programming to solve for ingredient combinations that satisfy minimum nutrient constraints at the lowest economic cost, subject to limits on inclusion rates and anti-nutritional factors.[98] For instance, software like Excel-based solvers or commercial tools (e.g., Brill Formulation) iteratively adjust proportions, prioritizing high-digestibility ingredients to reduce excess nutrients excreted as waste, which enhances environmental efficiency.[99] Recent advancements integrate artificial intelligence (AI) into least-cost formulation, augmenting linear programming with machine learning algorithms that process large datasets to predict ingredient interactions, nutrient bioavailability, and animal responses more accurately. AI enables dynamic optimization by incorporating real-time variables such as market prices, ingredient variability, and precision feeding data, thereby improving nutrient delivery, reducing formulation costs, and enhancing overall efficiency without compromising nutritional requirements.[8] In ruminants, formulations account for rumen microbial synthesis of proteins and volatile fatty acids, using systems like the Cornell Net Carbohydrate and Protein System to predict metabolizable energy yields from fibrous feeds, achieving up to 20% better accuracy in dairy cow predictions compared to simpler models.[8] Feed efficiency quantifies how effectively ingested nutrients convert to animal products, primarily via the feed conversion ratio (FCR), calculated as kilograms of feed per kilogram of live weight gain or output (e.g., milk or eggs).[100] Typical FCR values range from 1.4-1.8 for modern broilers, 2.5-3.0 for pigs, and 4.5-7.0 for feedlot cattle, with lower ratios indicating superior efficiency driven by genetic selection and precise diets.[101] Formulation directly impacts FCR by minimizing nutrient imbalances; for example, supplementing limiting amino acids like methionine in monogastrics can improve FCR by 5-10% by reducing protein catabolism for energy.[102] In ruminants, total mixed rations (TMRs)—homogeneous blends of forages, concentrates, and additives—enhance efficiency by preventing selective feeding, increasing dry matter intake uniformity, and boosting milk yield by 1-2 kg/day in dairy herds through better rumen pH stability.[103] [104] Advanced strategies further optimize efficiency, including exogenous enzymes (e.g., phytases releasing 0.15-0.20% additional phosphorus) to counter anti-nutritional factors in plant-based feeds, and precision feeding tailored to individual variability via sensors, potentially reducing FCR by 3-5% in swine.[105] Ruminants inherently exhibit lower efficiency (10-20% energy loss in rumen fermentation) than monogastrics due to methane production and microbial maintenance, but ionophores like monensin can improve beef cattle FCR by 5-7% by shifting rumen fermentation toward propionate.[106] Empirical data from controlled trials underscore that formulations ignoring bioavailability—such as over-relying on crude protein metrics—lead to inefficiencies, with balanced, digestible systems yielding 10-15% higher net returns in commercial operations.[107]Impact on Animal Health and Productivity
Balanced diets formulated to meet specific nutritional requirements enhance animal growth rates, reproductive performance, and overall health by optimizing energy utilization, protein synthesis, and immune function.[108] Studies indicate that access to high-quality feed correlates with increased weight gain in meat animals and higher milk yields in dairy cattle, with balanced rations potentially boosting net daily income by 10-15% for small-scale producers maintaining one to two cows.[109] Precision feed formulation further supports livestock productivity by aligning nutrient profiles with physiological demands, thereby reducing metabolic stress and improving milk quantity and quality.[110] Feed additives, including probiotics, enzymes, and phytogenics, contribute to better gut health, nutrient digestibility, and feed efficiency, leading to measurable gains in average daily weight gain and reduced mortality.[111] A meta-analysis across nine livestock species found that non-antibiotic additives positively affect performance metrics, immunity, and intestinal integrity, with effects moderated by dosage and animal type.[38] In poultry and swine, optimized diets have improved feed conversion ratios (FCR) by enhancing nutrient absorption, where lower FCR values—typically 1.5-2.0 for broilers and 2.5-3.0 for finishing pigs—indicate superior conversion of feed into body mass.[112][113] Conversely, nutritional deficiencies in feed, such as inadequate energy or minerals, impair immune response, cause weight loss, and diminish reproductive efficiency, with chronic cases linked to irreversible conditions like stunted growth in young animals.[114][5] Contaminants like mycotoxins in grains and forages exacerbate these issues by disrupting digestion, metabolism, and physiology, resulting in reduced productivity, immunosuppression, and organ damage even at subacute levels.[115][88] In ruminants and monogastrics, mycotoxin exposure has been associated with up to 20-30% drops in feed intake and growth performance, underscoring the need for rigorous quality controls to mitigate subclinical losses.[116]Primary Ingredients
Energy Sources (Grains and Carbohydrates)
Grains serve as the predominant source of carbohydrates in concentrated animal feeds, supplying starch that animals metabolize for energy needs such as maintenance, growth, and production.[117] Carbohydrates, primarily in the form of starch and structural fibers, constitute 60-70% of typical dairy cattle diets and provide volatile fatty acids via ruminal fermentation or direct glucose absorption in monogastrics.[118] In swine and poultry feeds, cereal grains deliver most dietary energy through highly digestible starch, with palatability enhancing intake.[119] Corn (Zea mays) dominates global and U.S. feed grain usage, accounting for over 95% of total feed grains in the United States as of 2025, due to its high starch content of approximately 72% on a dry-matter basis and gross energy of 3,840-4,450 kcal/kg.[117] [120] [121] Its digestible energy for pigs reaches about 90% of gross energy, supporting efficient weight gain in monogastrics, while ruminants benefit from ruminal starch fermentation yielding propionate for gluconeogenesis.[122] Processing methods like steam-flaking increase ruminal starch digestibility in cattle from 64% (dry-rolled) to 84-87% (steam-flaked or high-moisture corn), reducing undegraded starch escape to the intestine.[123] Other key grains include sorghum, barley, and wheat, each offering comparable energy but varying in fiber and protein. Sorghum provides similar starch levels to corn but lower digestibility in monogastrics due to kafirin proteins hindering enzymatic breakdown, making it a cost-effective alternative in arid regions.[124] Barley, with intermediate crude protein (9-10%), excels in ruminant feeds for its beta-glucans that promote rumen health, though excessive levels can reduce monogastric starch utilization without processing.[125] Wheat, higher in starch (up to 68%) than barley, supports high-energy finishing diets but risks acidosis in ruminants if overfed unprocessed, as its rapid fermentation elevates ruminal propionate.[126] Carbohydrate sources extend beyond grains to fibrous byproducts like beet pulp or molasses, which supply fermentable energy for ruminants via acetate production, complementing starch in balanced rations to optimize microbial protein synthesis and prevent digestive disorders.[22] In monogastrics, non-starch polysaccharides from grains influence viscosity and nutrient absorption, necessitating enzyme supplementation for optimal energy extraction.[127] Overall, grain selection balances energy density with digestibility, influenced by animal species: ruminants tolerate more fiber fermentation, while monogastrics prioritize starch accessibility for intestinal absorption.[128]Protein Sources (Plant and Animal-Based)
Plant-based protein sources dominate global animal feed formulations due to their abundance, cost-effectiveness, and scalability. Soybean meal, produced by extracting oil from soybeans via solvent processes, is the primary source, offering 47-49% crude protein in dehulled varieties and exhibiting high ileal digestibility of amino acids, often above 85% for lysine and methionine in monogastrics.[129][130] Its amino acid profile supports efficient protein synthesis in poultry and swine, though supplementation with synthetic methionine is common to address relative deficiencies.[131] Global soybean production reached 395 million metric tons in the 2023/24 season, with a significant portion processed into meal for feed, underscoring its role in supplying over 70% of plant protein needs in many diets.[132] Other plant sources include canola meal, which contains 36-40% crude protein but lower lysine levels requiring blending with soybean meal for balanced nutrition in swine feeds.[133] Sunflower meal provides 28-36% protein with high fiber content, limiting its use to ruminants where microbial fermentation aids digestibility.[133] These alternatives help mitigate soybean supply volatility but generally offer inferior amino acid quality and higher anti-nutritional factors like glucosinolates in canola, necessitating heat treatment or enzyme addition for optimal utilization.[134] Animal-based proteins, though less prevalent due to regulatory constraints and costs, deliver superior digestibility and essential amino acid completeness. Fish meal, rendered from small pelagic fish, typically contains 60-72% crude protein and serves as a high-quality bypass protein for ruminants while enhancing growth in aquaculture and young monogastrics through palatability and omega-3 fatty acids.[124] Its global market was valued at USD 9.5 billion in 2023, reflecting demand in carnivorous fish feeds where it comprises up to 20-50% of diets despite efforts to reduce inclusion via plant substitutes.[135] Regulations in the EU and US limit mammalian-derived proteins like meat and bone meal (MBM) in ruminant feeds to prevent bovine spongiform encephalopathy transmission, confining MBM—offering ~50% protein and rich phosphorus—to non-ruminant species such as poultry and swine at levels below 5% to avoid mineral imbalances.[136][137] Emerging animal-based options like insect meals from black soldier fly larvae provide 40-50% protein with favorable sustainability profiles, bypassing BSE risks and offering methionine-rich profiles comparable to fish meal, though scaling remains limited by production costs as of 2024.[138] Overall, plant sources prevail for economic reasons, while animal proteins excel in nutritional density but face biosecurity and environmental scrutiny.[124][133]Minerals, Vitamins, and Functional Additives
Minerals are inorganic elements essential for animal physiological functions, including bone formation, enzyme activation, and electrolyte balance, and are categorized as macrominerals (required in grams per day) and trace minerals (required in milligrams or micrograms per day).[139] Macrominerals such as calcium, phosphorus, magnesium, sodium, potassium, chlorine, and sulfur support structural integrity and metabolic processes, with deficiencies leading to conditions like milk fever in dairy cattle from calcium shortfall.[5] Trace minerals, including iron, copper, manganese, zinc, iodine, selenium, and cobalt, function as cofactors in metalloproteins and antioxidants; for instance, selenium and vitamin E together prevent white muscle disease in calves.[140] Requirements vary by species, age, and production stage; beef cattle need approximately 0.3-0.6% calcium and 0.2-0.4% phosphorus in dry matter intake, often necessitating supplementation in forage-based diets low in these elements.[141]| Mineral | Example Requirement (Beef Cattle, Growing) | Function | Source of Potential Deficiency |
|---|---|---|---|
| Calcium | 20-30 g/day | Bone health, muscle contraction | Grass hays low in legumes[33] |
| Phosphorus | 15-25 g/day | Energy metabolism, bone | Corn silage-heavy rations[141] |
| Zinc | 30-40 mg/day | Immune function, growth | Soils with high iron/manganese[140] |
| Copper | 10 mg/day | Enzyme activity, pigmentation | Alkaline soils antagonizing absorption[5] |
Application by Animal Species
Ruminants (Cattle, Sheep, Goats)
Ruminants possess a specialized digestive system featuring a rumen, where symbiotic microorganisms ferment fibrous plant material into volatile fatty acids, providing up to 70% of their energy needs through microbial breakdown of cellulose and hemicellulose that non-ruminants cannot efficiently digest.[153] This adaptation enables cattle, sheep, and goats to thrive on high-fiber forages such as grasses, legumes, and crop residues, which form the basis of their diets in both extensive grazing and intensive production systems.[154] Rumen function requires a minimum dietary neutral detergent fiber (NDF) level of 25-33% to maintain rumen motility, pH stability between 6.0 and 6.8, and prevent acidosis from excessive concentrate feeding.[155] Essential nutrients for ruminants include water, energy from carbohydrates and fats, proteins divided into rumen-degradable protein (RDP) for microbial growth and rumen-undegradable protein (RUP) for direct absorption, vitamins, and minerals like calcium, phosphorus, and magnesium.[156] Dry matter intake (DMI) varies by species, production stage, and diet; for example, lactating dairy cows typically consume 3-4% of body weight in dry matter daily, equating to 17-30 kg for a 600 kg animal, while growing beef cattle average 2.5-3% of body weight.[157] Sheep and goats exhibit similar patterns but with lower absolute intakes scaled to body size, around 2-3% for maintenance, increasing to 4% during lactation or growth; goats, as selective browsers, often require more diverse forages than cattle's grazing preference.[158] Protein requirements range from 9-16% of diet dry matter, balancing RDP (60-70% of total) to support rumen microbes synthesizing microbial protein, which supplies 50-80% of the host's amino acids.[159] Primary feeds consist of forages like pasture grasses, alfalfa hay, and corn silage providing bulk fiber and baseline energy, supplemented with concentrates such as corn, barley, or soybean meal in high-production scenarios to boost energy density without compromising rumen health.[160] Total mixed rations (TMR) are commonly formulated for confined cattle, blending forages (50-70% of diet) and concentrates to ensure uniform intake and minimize particle sorting, achieving feed efficiencies where 1 kg of dry matter supports 0.5-1 kg of milk or 0.1-0.2 kg of weight gain depending on breed and conditions.[154] For sheep and goats, diets emphasize legumes and browse for palatability, with grain supplementation limited to 20-30% to avoid digestive upset; in tropical systems, native grasses and shrubs suffice for maintenance but require mineral licks to address deficiencies in phosphorus or selenium.[161] Feed efficiency in ruminants is quantified via residual feed intake (RFI), where low-RFI animals consume 0.5-1 kg less dry matter daily for equivalent output, influenced by rumen microbial efficiency and digesta passage rates faster in goats (1.5-2 times cattle).[162] In beef cattle finishing, DMI averages 10-12 kg/day yielding feed conversions of 6-8 kg dry matter per kg gain; dairy systems target 1.5-2.0 kg milk per kg DMI.[163] Sheep achieve 5-7 kg dry matter per kg lamb gain on forage-grain mixes, while goats' browsing efficiency supports meat production on marginal lands with less supplemental input.[164] Proper formulation enhances productivity, reducing methane emissions per unit output by optimizing fiber fermentability and energy partitioning toward growth or lactation rather than maintenance.[165]Monogastrics (Poultry, Swine)
Monogastric animals, including poultry and swine, feature a simple stomach structure that precludes extensive microbial fermentation of fibrous feeds, unlike ruminants, thereby requiring diets emphasizing highly digestible energy and protein sources to support growth, reproduction, and health.[166] These species derive limited nutritional value from forages—typically 5-20% of needs—with the majority supplied by concentrates such as grains and oilseed meals.[94] Feed formulation adheres to guidelines from the National Research Council (NRC), which specify requirements for macronutrients, amino acids, minerals, and vitamins tailored to production phases.[167] [168] In poultry production, particularly broilers and layers, corn-soybean meal diets predominate, providing starch for energy and essential amino acids like methionine and lysine, which are often supplemented due to deficiencies in plant-based proteins.[169] Diets are phased—starter feeds with 22-24% crude protein for chicks transitioning to finisher rations around 18%—to optimize feed efficiency, achieving body weight gains of 50-60 grams per day in broilers under controlled conditions.[170] Swine nutrition similarly employs phase feeding: creep feeds for piglets (18-20% protein), grower diets (16-18%), and finisher rations (14-16%) to minimize excess nutrient excretion while meeting lysine requirements of 1.0-1.2% in growing phases.[171] Phytase enzymes are routinely added to enhance phosphorus availability from plant sources, reducing inorganic supplementation by up to 50% per NRC models.[172] Feed conversion ratios (FCR) serve as key metrics of efficiency; modern broiler operations report FCRs of 1.4-1.6 kg feed per kg gain, reflecting genetic and nutritional advances since 2010.[173] Swine exhibit higher ratios, averaging 2.8-3.2 kg feed per kg gain in grow-finish stages, influenced by factors like diet energy density (typically 3,300 kcal/kg metabolizable energy) and amino acid balancing.[173] [170] Empirical data indicate that precise formulation—using available phosphorus bases and split-sex feeding—lowers FCR by 5-10% compared to generic rations, directly correlating with reduced manure nutrient loads.[174] Emerging alternatives, such as insect meals or fermented by-products, show promise for partial protein replacement but require digestibility trials to avoid impairing growth rates observed in cereal-based baselines.[175]Aquaculture and Other Species
Aquaculture feeds are designed for carnivorous and omnivorous species such as salmon, tilapia, and shrimp, emphasizing high protein levels exceeding 25% and lipids above 6% to support rapid growth and metabolic demands.[176] Traditionally, these feeds incorporate fishmeal and fish oil sourced from wild forage fish like anchovies and herring, providing essential amino acids and omega-3 fatty acids.[177][178] Complete diets also include carbohydrates (15-20%), minerals, vitamins, and pigments for flesh coloration, with formulations tailored to species-specific needs—salmon feeds often feature 40-50% protein, while shrimp require 30-40% protein supplemented with crystalline amino acids like lysine at 1.6-2.1% of the diet.[179][180] Global formulated aquafeed production reached over 53 million metric tons in 2023, accounting for about 4.2% of total compound feed and enabling aquaculture output of approximately 94 million tons of aquatic animals in 2022.[181][182] Feed efficiency is high, with farmed fish and shrimp achieving a conversion ratio of 1.1 kg feed per kg biomass gain, outperforming many terrestrial livestock due to aquatic physiology and optimized diets.[183] To mitigate pressure on wild fisheries, alternatives like insect meals (e.g., black soldier fly), algae, and plant proteins are increasingly integrated, reducing fishmeal inclusion from historical highs while maintaining nutritional efficacy.[184][185] For other species, such as horses, feeds prioritize forage to mimic natural grazing, with requirements of 1-2% body weight in dry matter daily, primarily from hay or pasture, supplemented by concentrates like oats, barley, corn, and soybean meal for energy and protein during high activity or growth phases.[186][187] Companion animals like dogs and cats receive complete, balanced commercial diets formulated under regulatory standards to supply proteins from animal by-products and plants, fats, carbohydrates, and micronutrients tailored to life stage and health needs, though over-reliance on grains in some formulations has prompted shifts toward higher meat content.[188][189]Health Risks and Safety Concerns
Pathogen Transmission and Prion Diseases
Animal feed can serve as a vector for bacterial pathogens, including Salmonella enterica serovars and Shiga toxin-producing Escherichia coli (STEC), which enter the supply chain through contaminated ingredients such as grains exposed to animal feces, poor sanitation in milling processes, or cross-contamination during storage. These pathogens persist in feed due to its low moisture content and can survive pelleting or extrusion if temperatures are insufficient, leading to ingestion by livestock and subsequent gastrointestinal colonization or systemic infection. In cattle, swine, and poultry, Salmonella contamination rates in feed have been documented at 5-25% in surveys across Europe and North America, correlating with herd-level prevalence and shedding that amplifies zoonotic risks via undercooked meat or dairy products.[190][191][192] Pathogen transmission dynamics follow causal pathways where feed acts as an initial amplifier: contaminated lots spread via bulk transport, infecting multiple animals on farms, with persistence enhanced by biofilms in feed systems or rodent vectors. Empirical data from U.S. outbreaks, such as the 2007 recall of 35 million pounds of pet food linked to Salmonella from rice protein concentrate, underscore feed's role in broader contamination events affecting companion animals and potentially humans through handling. Regulatory interventions, including heat treatment standards (e.g., 85°C for 30 seconds in EU guidelines) and pathogen reduction programs like the U.S. FDA's Feed Safety Modernization Act of 2011, have reduced but not eliminated risks, as evidenced by ongoing isolations in 10-15% of tested poultry feeds in recent audits.[193][194] Prion diseases pose a unique, non-replicating infectious risk in animal feed, primarily through bovine spongiform encephalopathy (BSE), where misfolded prion proteins (PrP^Sc) from rendered ruminant tissues recycle into meat-and-bone meal (MBM) fed to cattle. This intraspecies amplification, driven by high-protein feed practices in intensive farming, caused the UK epidemic: first cases confirmed in 1986, escalating to 36,680 annually by 1992 peak, with total confirmed bovine cases exceeding 184,000 by 2010. Prions resist standard rendering (typically 133°C for 20 minutes at 3 bar), remaining infectious in feed at doses as low as 1 mg, inducing conformational change in host PrP^C and inexorable neurodegeneration over 4-5 years incubation.[195][196][197] Global responses included the EU's 1994 ban on mammalian MBM in ruminant feed and the U.S. FDA's 1997 rule (21 CFR 589.2000) prohibiting most mammalian proteins in ruminant diets, which halted classical BSE transmission and reduced incidence to atypical cases (e.g., 1-2 per million tested cattle annually post-2005). Variant Creutzfeldt-Jakob disease (vCJD) in humans, causally linked to BSE via consumption of contaminated beef, resulted in 178 UK cases by 2016, with prions detectable in lymphoid tissues facilitating dietary exposure. Other livestock prions, like scrapie in sheep, show limited feed transmissibility compared to BSE but highlight rendering vulnerabilities, as experimental oral dosing with 5g infected brain material induced disease in 30-50% of recipients. Ongoing surveillance confirms feed bans' efficacy, though illegal recycling or atypical strains (e.g., H-type BSE) persist as low-probability vectors.[198][199][200]Antimicrobial Use and Resistance
Antimicrobials, including antibiotics, have been incorporated into animal feed primarily for growth promotion, improved feed efficiency, and disease prophylaxis in intensive livestock production systems. Globally, an estimated 99,502 tonnes of active antimicrobial ingredients were used in cattle, sheep, chickens, and pigs in 2020, with a substantial portion administered via feed additives. [201] In the 2010s, approximately 70% of all antibiotics produced worldwide were applied to farm animals, often through medicated feeds to prevent infections in crowded conditions. [202] This practice persists predominantly in regions with high-density farming, where subtherapeutic doses enhance weight gain by altering gut microbiota, though efficacy varies by species and antimicrobial class. [203] Prolonged low-level exposure in feed selects for antimicrobial-resistant bacteria within animal populations, elevating resistance prevalence in pathogens like Salmonella and Campylobacter. Peer-reviewed studies confirm that overuse in livestock fosters resistant strains, with reductions in antimicrobial use correlating to up to 39% decreases in resistant bacteria isolated from animals. [204] In conventional farming systems relying on medicated feeds, resistance rates in zoonotic bacteria exceed those in antibiotic-free operations, as evidenced by meta-analyses comparing prevalence across production models. [205] Mechanisms include horizontal gene transfer among bacteria in the animal gut and selective pressure favoring resistant mutants, amplifying risks in monogastric species like poultry and swine where feed-based delivery is common. [206] Transmission of resistance from feed-amended livestock to humans occurs via direct foodborne pathways, environmental dissemination through manure, and indirect contacts, contributing to human antimicrobial resistance (AMR) burdens. Antibiotic-resistant bacteria from treated animals have been detected in meat products, with genomic evidence linking livestock-origin strains to human infections for over 40 years. [207] Quantitatively, a 1% increase in farm animal antimicrobial use associates with a 0.04% rise in human AMR prevalence, underscoring a causal pathway despite confounding factors like human prescribing practices. [208] Environmental release from feedlot waste further propagates resistance genes into soil and water, potentially entering human microbiomes via produce or seafood, though direct attribution remains challenging due to multi-source exposures. [209] Regulatory responses have curbed feed-based antimicrobial use in several jurisdictions to mitigate resistance risks. The European Union prohibited antibiotics as growth promoters in animal feeds effective January 1, 2006, resulting in measurable declines in certain resistant pathogens in EU livestock. [210] In the United States, the FDA's Guidance for Industry #213, implemented from 2017, phased out over-the-counter sales of medically important antimicrobials for production purposes, including feed additives, leading to a 2% drop in sales for food-producing animals in 2023. [211] China banned antimicrobial growth promoters in feeds in 2020, except for certain traditional medicines, aligning with global trends toward veterinary oversight. [212] These measures prioritize therapeutic use under prescription, though enforcement varies and illegal use persists in some markets. Despite reductions, challenges include the economic incentives for prophylactic feed supplementation in pathogen-prone intensive systems and the scarcity of viable alternatives like vaccines or probiotics, which do not universally match prior productivity gains. Empirical data indicate that bans reduce animal-level resistance without consistently translating to proportional human health benefits, suggesting complex transmission dynamics. [213] Ongoing surveillance by bodies like the World Organisation for Animal Health tracks global trends, revealing a 13% decline in animal antimicrobial use from 2018 to 2021, yet rising resistance in key pathogens underscores the need for integrated One Health strategies beyond feed restrictions alone. [214]Contaminants and Toxins
Mycotoxins, secondary metabolites produced by fungi such as Aspergillus, Fusarium, and Penicillium species, represent the most prevalent toxins in animal feed, particularly in cereal grains, silage, and forages stored under humid conditions.[215] Global surveys indicate multi-mycotoxin contamination affects up to 80% of feed samples, with ochratoxin A (OTA) detected in 51% of cases, zearalenone (ZEN) in 38%, deoxynivalenol (DON) in 33%, and aflatoxins (AFs) in 17%.[216] These toxins originate from pre- and post-harvest fungal growth influenced by weather, crop stress, and improper storage, leading to sporadic annual variations even in the same regions.[217] In livestock, ingestion causes acute effects like vomiting and feed refusal (e.g., from DON) or chronic issues including reduced growth rates, impaired reproduction (ZEN mimics estrogen), liver damage, and immunosuppression, with carry-over to milk, meat, and eggs posing human risks such as carcinogenicity for aflatoxin B1.[115][88] Heavy metals including arsenic (As), cadmium (Cd), lead (Pb), and mercury (Hg) enter feeds via soil uptake, phosphate fertilizers, mining runoff, and industrial pollution, accumulating in plant-based ingredients like grains and forages. FDA monitoring from 2015-2017 detected these in animal foods, with Cd levels higher in plant meals and Pb in supplements, though most below action levels; chronic exposure in ruminants and monogastrics disrupts enzyme function, causes oxidative stress, and bioaccumulates in organs, transferring to edible tissues and milk at rates up to 10-20% for Cd in cattle.[218] Regulations like EU maximum limits (e.g., 1 mg/kg Cd in feed) and U.S. guidance based on NRC toxicity data aim to cap intake, but enforcement varies, with higher risks in regions using contaminated fertilizers.[219] Pesticide residues, such as organophosphates and glyphosate, persist from crop treatments and enter feeds through treated grains or byproducts like soybean meal, with low-level detection common but exceeding tolerances rare under regulatory oversight.[220] EPA sets feed tolerances based on animal metabolism and human exposure models, ensuring residues do not accumulate significantly in meat or dairy; for instance, glyphosate in livestock feed shows minimal carry-over (<1% to tissues) and no established health risks at approved levels, though chronic low-dose effects like gut microbiome disruption remain under study.[221][222] Persistent organic pollutants like dioxins (PCDD/Fs) and polychlorinated biphenyls (PCBs) contaminate feeds via industrial byproducts in fats, fishmeal, or recycled oils, with bioaccumulation highest in fatty tissues of fed animals.[223] Notable incidents include the 1999 Belgian crisis, where 50 kg of PCBs and 1 g of dioxins in citrus pulp feed additive affected poultry, pork, and eggs, prompting widespread culls and exports bans due to elevated levels in products (e.g., dioxins in pork up to 10-fold above limits).[224] Such events highlight feed as a primary vector, though post-incident monitoring shows ambient levels in EU feeds typically below 0.75 ng WHO-TEQ/kg, with animal health effects including reproductive toxicity and immune modulation at high exposures.[225] Natural plant toxins, such as gossypol in cottonseed meal or phytoestrogens in soy, occur endogenously but can toxify feeds at high inclusions; gossypol binds iron in monogastrics, reducing fertility, while regulations limit usage (e.g., <10% in swine diets).[215] Overall, while contaminants pose verifiable risks—evidenced by productivity losses estimated at 5-10% in mycotoxin-affected herds—empirical data from surveillance programs indicate effective mitigation through testing and limits, countering claims of systemic failure absent widespread outbreaks.[226][75]Environmental and Sustainability Dimensions
Resource Consumption and Emissions Data
Animal feed production utilizes approximately 33% of global cropland for crops such as maize, soybeans, and other concentrates destined for livestock.[227] This equates to roughly 456 million hectares based on 2023 estimates of total arable land at 1,381 million hectares.[228] When including grazing lands, livestock systems occupy about 77% of agricultural land worldwide, though pasture-based feeds differ from crop-based concentrates in resource intensity.[229] Water consumption for feed production dominates livestock water use, accounting for over 90% of total requirements in many systems.[230] Globally, blue and green water footprints for livestock feed total around 4,387 cubic kilometers annually, representing 41% of agricultural water use.[231] Feed crops like soybeans and maize exhibit high variability; for example, irrigated maize for feed can require 1,000-2,000 cubic meters of water per ton produced, with green water (rainfall) comprising the majority in rain-fed regions.[232] Energy inputs in feed production arise primarily from crop cultivation (e.g., fertilizer manufacturing and tillage), processing (e.g., grinding and pelleting), and transport. Pelleting alone consumes up to 25 kWh per ton of feed.[233] Globally, animal-based food systems, driven largely by feed demands, account for 60% of agriculture's energy footprint despite providing only 18% of calories.[234]| Resource/Emissions Category | Key Data Point | Source |
|---|---|---|
| Land Use | 33% of cropland for feed crops | FAO (2006, reaffirmed in recent analyses)[227][235] |
| Water Use | 4,387 km³/year (blue + green) for feed | Alexander et al. (2020)[231] |
| Energy Intensity | Up to 25 kWh/ton for pelleting | Redecker & Thoben (2012)[233] |
| GHG Emissions Contribution | Feed supply chains ~40-70% of monogastric lifecycle emissions (e.g., poultry, swine); lower for ruminants due to enteric sources | FAO LEAP guidelines; Poore & Nemecek (2018)[67][236] |