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Runt
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Runt
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A runt is an animal that is unusually small for its species.[1] In veterinary medicine, a runt may also be described using terms such as low-birth weight, intrauterine growth restriction,[2] and small for gestational age.[3] An animal may be defined as small for gestational age (SGA) depending on different criteria, such as size in comparison to littermates',[4] as percent of maternal body weight,[5] as a specific neonate weight threshold for the breed or species,[6] and as different body proportions displayed by runts.[2]

Runts face many challenges in comparison to their normal birth weight peers - they are more likely to contract diseases,[7] and die in the neonatal period, have lower glycogen stores, suffer from developmental delays, insulin resistance,[2] hypothermia,[5] and low blood pressure.[8] Runts are also associated with economic losses in farm animals - SGA adult cows give smaller milk yields and suffer from infertility,[7] intrauterine growth restricted (IUGR) piglets have modifications in their muscle tissue that may affect the taste of their meat, adult IUGR sows have smaller litter sizes and lower birth weight piglets in their litters[2] and adult low birth weight ewes may have poorer quality fleeces.[9]

Causes

[edit]

SGA has been best studied in pigs, both due to industry pressures of high mortality rates of preweaning piglets and the use of pig as a model organism in science. Runts are caused by interplay between genetics, environment in utero, maternal environment and care. Breeding for larger litter sizes has resulted in there being born more piglets than the teats of the sow, longer birthing times and more hypoxic young. Further causes of fetal malfunctioning can be a circovirus infection, maternal malnutrition or a small or inconveniently placed placenta.[2][6]

In cattle and sheep, an additional reason may be hot weather during pregnancy.[10][11] In dairy cows, a contributing factor may be lactating while pregnant, which can overtax the cow's ability to provide sufficient nutrients to the fetus. Nulliparous cows are more at risk of giving birth to SGA calves, and on average give birth to calves of a lower birth weight.[11]

In dogs, a larger litter size may cause more low weight puppies to be born.[5] Typically low weight puppies, like piglets, have smaller placentas in comparison to their normal body weight littermates.[12]

In cats, younger mothers are more likely to give birth to kittens with lower body weight. Likelihood of giving birth to low body weight kittens increases if there is at least one stillbirth in the litter.[13]

Management

[edit]

For companion animals such as dogs, assisting with whelping, using apgar scoring and monitoring weight to identify at-risk puppies has been proven to lower mortality rates and equalize early growth among littermates.[12]

However, it is the identification of at-risk puppies that presents a unique challenge in dogs, as dog breeds can vary in weight from less than 1 kg to 120 kg. This discrepancy in size can make it hard to create a uniform guideline for care which breeders and veterinarians can implement in practice. Several identifying tools have been proposed, such as puppy weight - mother weight ratio, which can help identify low birth weight mongrel puppies[5] or breed-specific thresholds, which can be more useful in identifying underweight purebred puppies, as the birth weight of puppies can vary quite a bit among same adult size large and giant breeds.[14]

For livestock like swine, labor-intensive birth assistance has been identified as a major mitigating factor in runt mortality and future outcomes, however such a strategy is cost ineffective in intensive animal farming. Instead, the recommended strategy is managing the sow's nutritional intake and not breeding IUGR piglets.[2]

In cows, it has been found that runt calves are less likely to be effective milk producers and also tend to produce smaller calves in turn. It has been suggested that it would be more effective to redirect SGA calves to veal production, and preferentially breed calves of an average size and good productivity.[7]

See also

[edit]

References

[edit]
[edit]
Revisions and contributorsEdit on WikipediaRead on Wikipedia

Runt

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from Grokipedia
A runt is an animal that is unusually small in size compared to others of its kind, most commonly referring to the smallest and often weakest member of a born to the same mother, such as a piglet or . The term originated in English around 1500, initially describing an old or decayed , before evolving to signify anything stunted or , including animals and, by extension, people. In , runts are typically identified by , which places them at greater for complications like , , and preweaning mortality due to for and maternal care. For instance, in swine production, piglets weighing less than 900 g (about 2 lb) at birth face up to an 83% in the first three days if not given special intervention, while those under 1 kg are generally at higher . While the concept applies across species, it is particularly prevalent in pigs, where large litter sizes increase the likelihood of intrauterine growth variation leading to runts; the term is also commonly applied to dogs. Efforts to mitigate runt outcomes include supplemental feeding, fostering to nurse sows with smaller litters, and selective breeding to reduce birth weight variability. Informally, "runt" is also used derogatorily to describe a small or weak person, though this usage is considered offensive.

Definition and Characteristics

Definition

A runt is defined as the smallest and often weakest in a mammalian , characterized by lower relative to its siblings and sometimes reduced vitality at birth. Unlike terms such as "," which describe chronic developmental delays from ongoing nutritional or environmental deficits not tied to litter dynamics, or "undersized," which may indicate small stature without implying inherent , "runt" specifically denotes the comparative smallest member of a single birth group. The phenomenon is most commonly observed in multiparous species that produce litters, including pigs, dogs, cats, and rats, where for maternal resources can accentuate disparities. It occurs occasionally in larger mammals like , particularly in cases of twin foals where one may receive fewer nutrients . Runts often exhibit low birth weights as a key indicator, distinguishing them from average littermates without exploring further physiological traits. Etymologically, "runt" emerged in the early as a provincial English term for an old or decayed , of uncertain origin but possibly linked to Dutch "rund" meaning ox. By the late 1500s, its meaning expanded to denote a small or inferior specimen, particularly in agricultural settings applied to undersized such as pigs or , and by the specifically to the smallest member of a .

Physical and Behavioral Traits

Runts, defined as the smallest in a , exhibit distinct physical traits at birth that set them apart from their littermates, primarily characterized by significantly reduced size and . In porcine litters, runt piglets typically have birth weights 20-50% below the litter average, often falling under 1 kg for commercial breeds, compared to the typical 1.3-1.6 kg range for normal piglets. This low birth is accompanied by proportionally smaller body dimensions, including shorter length and reduced girth, contributing to their overall underdeveloped appearance. Underdeveloped organs further highlight the vulnerability of runts, with (IUGR) leading to asymmetrical growth patterns. In piglets, this manifests as smaller livers, lungs, and hearts relative to body size, alongside diminished fat reserves and stores, which impair and energy availability in the early postnatal period. Similarly, in canine litters, runt puppies display low birth weights—often classified as below 100-150 g for and small breeds—resulting in immature organ systems, such as reduced liver and function, and overall frailty. These physical disparities underscore the heightened susceptibility of runts to environmental stresses immediately after birth. Behaviorally, runts demonstrate reduced vitality and coordination compared to their siblings, often appearing lethargic and less responsive. In both porcine and canine neonates, weaker suckling reflexes hinder effective , leading to inadequate intake and competition disadvantages within the litter. Motor skills are also delayed, with runt piglets taking longer to stand and walk—sometimes up to several hours beyond the norm—while runt puppies exhibit diminished crawling vigor and slower reflex responses. These indicators of low vigor emphasize the need for close monitoring in the critical first days of life.

Etiology

Genetic Factors

In multiparous species such as pigs and cattle, a primary mechanism contributing to runt formation involves unequal placental sharing during gestation, resulting in (IUGR) for subordinate fetuses that receive fewer nutrients compared to dominant littermates. This developmental process is influenced by polygenic traits that regulate fetal size and placental efficiency, with quantitative trait loci (QTLs) on bovine (BTA6) identified as key modulators of fetal growth, where specific alleles can increase by up to 3.78 kg. estimates for fetal growth traits range from 0.2 to 0.6 in , indicating a substantial genetic component to variations in litter birth weights that predispose certain individuals to runt status. Specific genetic contributors to runt development include polygenic inheritance patterns affecting overall fetal size, as seen in breed differences where certain lines exhibit greater uniformity in litter weights due to selective breeding for growth-related genes. In rare cases, mutations disrupting the insulin-like growth factor 1 (IGF-1) pathway, such as the IGF1 allele fixed in small dog breeds or the R204H variant in the IGF1R gene, lead to reduced circulating IGF-1 levels and proportionally smaller offspring, manifesting as runts with low birth weights. These disruptions impair growth signaling, contributing to IUGR independently of litter competition in affected individuals. Litter dynamics further highlight genetic influences on runt formation through uterine position effects on blood flow in linear-utered species like pigs, where fetuses at the cervical end or middle of the horn experience reduced vascular supply, making them more prone to becoming runts compared to those at the ovarian end. This positional disparity arises from inherent variations in placental vascularization, with within-litter birth weight variation showing low to moderate heritability of 0.08–0.12, suggesting genetic selection could mitigate but not eliminate such outcomes. These genetic and positional factors manifest in physical traits such as low birth weight, typically under 1 kg in pigs, distinguishing runts from littermates.

Environmental and Nutritional Influences

Inadequate maternal during , particularly deficiencies in protein or caloric intake, can create resource scarcity in the , leading to uneven distribution among fetuses and contributing to the development of as the smallest offspring. Studies in have demonstrated that underfed sows produce litters with greater within-litter variation, resulting in a higher proportion of low-birth-weight piglets weighing 1.1 kg or less, which are classified as due to impaired muscle fiber formation and reduced growth potential from limited . Environmental stressors such as or exposure in pregnant dams disrupt hormonal balance, often elevating levels that impair fetal growth and exacerbate size disparities within litters. For instance, stress in sows reduces feed intake and increases physiological strain, leading to lower average piglet birth weights and shorter periods, which heighten the risk of smaller, weaker offspring. Similarly, from group housing promotes sustained elevation, negatively impacting and piglet viability. Prenatal exposure to toxins, such as mycotoxins in contaminated feed, further compromises fetal development by inducing and smaller litter members. In and models, aflatoxins from maternal diet have been associated with reduced fetal weight and impaired growth, correlating with the emergence of through mechanisms like disrupted uptake and developmental . Perinatal complications, including difficult births (dystocia) or delayed delivery, can intensify size differences by prolonging labor and increasing stress on later-born fetuses, which are often the smallest in the litter. In , dystocia events, defined by birth intervals exceeding 45 minutes, are more frequent with later birth orders and contribute to higher mortality or weakness in small piglets, amplifying runt characteristics through oxygen deprivation or exhaustion during delivery. These external factors can interact with genetic predispositions to heighten runt incidence, underscoring the role of modifiable environmental conditions in .

Health Implications

Common Health Complications

Runts face significant risks of shortly after birth, primarily due to their limited fat reserves and inefficient mechanisms, exacerbated by a higher body surface-to-volume that accelerates heat dissipation compared to larger littermates. In piglets, this vulnerability is particularly pronounced, as low-birth-weight individuals, often classified as runts, experience rapid cooling when exposed to ambient temperatures below their . Immune system deficiencies further compound health challenges for neonatal animals, including , stemming from underdeveloped thymic tissue that impairs T-cell maturation and overall in conditions like syndromes. This leads to heightened susceptibility to infections, including bacterial , which can overwhelm the weakened defenses in canine during the neonatal period. Organ-specific complications are also common, with runts exhibiting gastrointestinal immaturity, including delayed enzyme development that hinders nutrient absorption and promotes . These issues manifest as persistent lethargy and inadequate growth, directly linked to the runt's intrauterine constraints. In feline runts, fading kitten syndrome exemplifies these vulnerabilities, characterized by rapid onset of , , and metabolic instability that can prove fatal within days of birth.

Survival and Long-Term Outcomes

Runts, particularly in livestock such as piglets, face significantly elevated mortality risks during the neonatal period compared to their littermates. For instance, piglets with birth weights of 1.11 kg or less exhibit a preweaning of approximately 34.4%, accounting for 43% of total preweaning deaths in affected litters, with many losses occurring in the first week due to factors like and . In untreated cases, this rate can approach 50% for those below 1 kg, as low birth weight compromises colostrum intake and . Catch-up growth is possible for some runts if nutritional support is provided early, allowing certain piglets to reach near-normal size by weaning. However, many remain smaller into adulthood, exhibiting reduced growth rates and lower lean meat yield at slaughter, which impacts overall productivity in farming contexts. Health complications such as infections further hinder this potential, serving as key barriers to survival and development. Long-term outcomes for surviving runts vary by species and management. In , female pigs born at low weights (<1 kg) demonstrate compromised reproductive performance, producing about 4.5 fewer piglets over three parities and experiencing higher removal rates due to anestrus (up to 22.9% vs. 9.6% in heavier cohorts). This leads to reduced lifetime productivity and shorter herd longevity. In companion animals , runts that survive the neonatal period—where overall mortality can reach 30%, with half in the first week—often achieve normal adult size and health with proper care, though they may carry a higher of congenital issues if underlying causes persist. Early intervention in farmed environments markedly improves , elevating rates to 80-90% through measures like fostering and monitoring, compared to higher natural losses in uncontrolled settings. Factors such as threshold and uniformity play critical roles in these outcomes, emphasizing the importance of timely identification.

Management and Care

Interventions in Livestock

In livestock production, particularly in swine operations, runt piglets—defined as those with birth weights typically below 1.11 kg (2.45 lb) or exhibiting physical signs such as a dolphin-shaped head and backward-pointing ears—are identified immediately after birth through routine weighing and during attended farrowings. This early detection is crucial, as these piglets face heightened risks of due to from larger littermates for access to the sow's teats. To mitigate this, producers often implement separation strategies, such as split suckling—temporarily removing stronger piglets for 1-2 hours to allow runts priority nursing—or cross-fostering into smaller litters within 12-48 hours post-farrowing, ensuring the runts receive adequate while minimizing stress. Nutritional interventions form the cornerstone of runt , focusing on rapid provision of and immunoglobulins to combat and low vitality. Tube-feeding protocols typically involve administering 10-15 ml of sow or bovine , or a replacer, every 6-12 hours for the first 1-2 days using a 6-7 inch stomach tube or , with total intake targeted at least 250-300 ml (about 9 ounces) within the initial 24 hours; smaller (e.g., 0.9 kg or 2 lb) may require 5-6 feedings, adjusted by body weight to prevent aspiration. For porcine showing signs of , solutions can be incorporated into these feedings to restore and support metabolic recovery, often alongside supplemental sources like dextrose if intake remains insufficient. Monitoring protocols in commercial pig and cattle operations emphasize vigilant oversight to detect complications early. Runts are placed in warming boxes or under heat lamps maintaining 29-35°C (85-95°F) to prevent chilling, with body temperature checked frequently (target 35-38°C or 95-100°F) and veterinary assessments for infections conducted twice daily, including observations for skin tautness indicating proper hydration and nutrition. In cases of severe hypothermia, interventions like intraperitoneal saline injections (15 ml at 45°C or 113°F) can boost survival by aiding thermoregulation. These measures have been shown to improve preweaning survival rates for runts, aligning with broader outcomes where targeted care reduces overall litter mortality. Economically, interventions for offer a favorable cost-benefit in production, where low-birth-weight piglets account for up to 43% of preweaning deaths despite comprising only 15% of . The cost of reducing mortality by 1 percentage point ranges from €0.4-0.5 per piglet through low-input methods like and supplemental feeding, with profitability highest in operations facing baseline rates below 90%. For instance, successfully one additional piglet per in a 50-sow herd can generate an extra $3,000 annually, assuming $30 per market , while avoiding selective of runt-prone sows supports 10-15% improvements in herd-wide without major breeding overhauls. Such strategies enhance overall by integrating welfare improvements with efficient resource allocation in large-scale farming.

Support for Companion Animals

Support for companion animals born as runts in canine and feline litters focuses on individualized, welfare-oriented strategies to enhance survival and in home settings. Owners and veterinarians often implement hand-rearing techniques for runts unable to compete effectively for maternal milk, using specialized nursing bottles filled with commercial milk replacers formulated for puppies or kittens, such as those containing DHA for brain development. Feeding occurs every 2-4 hours initially, with careful monitoring to prevent aspiration, and transitions to by 3-4 weeks of age. Fostering with a surrogate mother—typically a lactating with similarly aged offspring—can provide essential maternal care and ; introductions involve rubbing puppies or kittens with the surrogate's bedding to familiarize scents and using a muzzle for safety during initial meetings. Creating a quiet, draft-free environment is crucial, maintaining temperatures of 85-90°F (29-32°C) for newborns and 55-65% humidity to mimic the , reducing stress on these fragile animals whose smaller physical traits demand gentle handling to avoid injury. Veterinary interventions complement home efforts, particularly for runts exhibiting or . Subcutaneous fluid administration, using warmed solutions like lactated Ringer's, supports hydration in weak neonates when oral intake is insufficient, often performed at home under guidance after initial clinic demonstration. Antibiotics such as amoxicillin are prescribed for bacterial infections common in compromised runts, like those causing fading puppy or syndrome, following diagnostic cultures to ensure . Growth monitoring involves daily weighing with standardized charts through the first 6 months, tracking against breed-specific percentiles to detect hypoglycaemia or nutritional deficits early; veterinarians may recommend supplements if gains lag below 5-10% body weight weekly in early stages. Surviving pet runts may display long-term timidity due to early competition or health challenges, necessitating behavioral support through structured starting at 3-8 weeks. Positive techniques, including treat rewards during gradual exposures to new people, sounds, and environments, help build confidence; for instance, short, calm sessions in a prevent overwhelming the animal. Ethical decisions balancing against intensive care hinge on quality-of-life assessments, with the (AVMA) advocating tools like the HHHHHMM scale—evaluating hurt, hunger, hydration, hygiene, happiness, mobility, and good days versus bad—to guide owners toward humane outcomes for runts with poor prognoses, prioritizing suffering prevention over prolonged intervention.

References

  1. https://www.merriam-webster.com/dictionary/runt
  2. https://www.dictionary.com/browse/runt
  3. https://www.etymonline.com/word/runt
  4. https://pmc.ncbi.nlm.nih.gov/articles/PMC7145795/
  5. https://www.pubs.ext.vt.edu/APSC/apsc-195/apsc-195.html
  6. https://pmc.ncbi.nlm.nih.gov/articles/PMC4471594/
  7. https://dictionary.cambridge.org/us/dictionary/english/runt
  8. https://www.whole-dog-journal.com/puppies/what-is-the-runt-of-the-litter/
  9. https://www.rover.com/blog/litter-runt/
  10. https://www.petscare.com/news/post/understanding-runt-of-the-litter
  11. https://articles.hepper.com/runt-of-the-cat-litter-vet-answer/
  12. https://www.newscientist.com/article/mg16121682-500-a-runt-for-life/
  13. https://www.oed.com/dictionary/runt_n
  14. https://dr.lib.iastate.edu/server/api/core/bitstreams/8ace54bc-8a8a-4f15-84af-4c9870b97429/content
  15. https://pmc.ncbi.nlm.nih.gov/articles/PMC7200817/
  16. https://www.sciencedirect.com/science/article/pii/S1751731125001739
  17. https://pmc.ncbi.nlm.nih.gov/articles/PMC10617784/
  18. https://bmcvetres.biomedcentral.com/articles/10.1186/s12917-020-02577-z
  19. https://www.everypaw.com/all-things-pet/puppy-development-1-8-weeks-old
  20. https://www.researchgate.net/publication/335264564_Relationship_between_placental_characteristics_and_puppies%27_birth_weight_in_toy_and_small_sized_dog_breeds
  21. https://www.cambridge.org/core/journals/animal-science/article/social-behaviour-of-domestic-animals-vi-a-note-on-some-characteristics-of-runts-in-pigs/13D4ED50A1734FBBD24998AEC865375B
  22. https://www.sciencedirect.com/science/article/pii/S0167587712003935
  23. https://pmc.ncbi.nlm.nih.gov/articles/PMC2778990/
  24. https://pmc.ncbi.nlm.nih.gov/articles/PMC3511640/
  25. https://pubmed.ncbi.nlm.nih.gov/12661639/
  26. https://www.k-state.edu/media/newsreleases/feb16/runts2216.html
  27. https://extension.umn.edu/swine-production-management/heat-stress-swine-affects-production
  28. https://onlinelibrary.wiley.com/doi/10.1002/mrd.22844
  29. https://pmc.ncbi.nlm.nih.gov/articles/PMC9039259/
  30. https://link.springer.com/article/10.1007/s12550-019-00384-6
  31. https://pmc.ncbi.nlm.nih.gov/articles/PMC8659025/
  32. https://www.veterinaryworld.org/Vol.14/July-2021/16.pdf
  33. https://pmc.ncbi.nlm.nih.gov/articles/PMC8309949/
  34. https://www.frontiersin.org/journals/veterinary-science/articles/10.3389/fvets.2022.1023294/full
  35. https://www.researchgate.net/publication/51259075_Possible_Association_of_Thymus_Dysfunction_with_Fading_Syndromes_in_Puppies_and_Kittens
  36. https://vcahospitals.com/know-your-pet/puppy-fading-puppy-syndrome-in-dogs
  37. https://www.nature.com/articles/pr2001212
  38. https://www.petmd.com/cat/conditions/fading-kitten-syndrome
  39. https://pmc.ncbi.nlm.nih.gov/articles/PMC10845402/
  40. https://academic.oup.com/tas/article/3/2/633/5511750
  41. https://pmc.ncbi.nlm.nih.gov/articles/PMC5420136/
  42. https://doi.org/10.1016/j.livsci.2015.12.008
  43. https://porkgateway.org/resource/baby-pig-management-birth-to-weaning/
  44. https://pmc.ncbi.nlm.nih.gov/articles/PMC9158370/
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