Genotype and managing birth weight and status as determinants of kid/lamb mortality in small ruminants

Abstract

One principal source of unsubstantial meat production efficiency in commercial small ruminants is high kid/lamb mortality, where a larger proportion of kid/lamb crop fails to reach marketable age resulting in immense economic losses. There is apparent evidence accrued through extensive studies which point to the fact that heredity and some non-genetic factors drive kid/lamb mortality in goats and sheep production. In this respect, mortality of kids/lambs may vary with genotype, nutrition, litter size, dam age and parity order, nutrition, sex and age of kid/lamb and season and year of kidding/lambing. The present review will give an insight on the influence of genotype, birth weight and birth status as determinants of mortality in goat and sheep. The resultant effect of genotype on kid/lamb mortality is associated with traits imparted to both dams and/or kid/lamb such as birth weight size related to difficult birth, kid/lamb viability after kidding/lambing and maternal characteristics. Low birth weight kid/lamb may die due to failure to adapt to life after birth, incompetence to sustain body temperature as a result of low energy body reserves at birth result into death, low kid/lamb potency and poor maternal attachment exposes kid/lambs to less survival chances. On the other hand, multiple birth has an adverse effect on kid/lamb survival due to lower birth weight as litter size increases, which is a lead factor to more hazard to mortality. The major reason for high mortality in underweight kid/lamb at birth is probably due to lack of suckling and/or exposure to low body temperatures. Mature dams give birth to heavier kids and provide enough milk to nursed kids/lambs promoting faster growth rates subsequently enhancing survivability of kids/lambs. There is potentiality of manipulation of husbandry practices focusing on ensuring that all born kids/lambs are as close as possible to the acceptable birth weight average for that specific breed of choice. It should be noted that due to multifaceted nature of the determinants of mortality it is reasonable to assume that appreciation of specific cause and occurrence of kids’/lamb mortality could be advantageous to minimise mortality rates. A total eradication of kid/lamb mortality is probably unachievable as a result partly targeting the control of both environmental and animal-related factors is of paramount importance. High kid/lamb mortality necessitate for good management practices and improved dam nutrition to support nursing of multiple birth, in addition to the exploitation of crossbred’s livability and survivability. The present review gives an insight on the determinants of mortality and associated factors in goat and sheep meat production.