Runt

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

Runts face many challenges in comparison to their normal birth weight peers - they are more likely to contract diseases, and die in the neonatal period, have lower glycogen stores, have developmental delays, insulin resistance, hypothermia, and low blood pressure. Runts are also associated with economic losses in farm animals - SGA adult cows give smaller milk yields and have infertility, 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 and adult low birth weight ewes may have poorer quality fleeces.