Phenotypic characteristics and factors associated with Assaf lamb body weight and morphology

Abstract The phenotypic characteristics of animals are result of the complex interaction of a number of genetic and non-genetic factors, which usually act simultaneously and it is difficult to determine the degree of influence of each of them. The goal of this study was to describe Assaf lamb morphology and its relationship with body weight (BW) at various ages, which had not previously been described in Jordan, and only adult Assaf had been described globally. BWs and phonotypical characteristics measurements were taken on 405 lambs, 208 lambs at birth (within three days of birth), 96 lambs at weaning (around 60 days), and 101 lambs at marketing age (around 120 days). The measurements were; withers height (WH), body length (BL), chest girth (CG), chest depth (CD), head length (HL), head width (HW), rump length (RL), RW (RW), shoulder width (SW), shin circumference (SC), foreleg height (FLH), rump height (RH) and rear leg height (RLH). Month of birth (MO) significantly (P < 0.001) affected BW and all morphological characteristics except CD and RW at birth. At weaning BW weight, HL, CG, RL, CD, SW, and RW were significantly (P < 0.001) affected by MO. MO has an effect on BW, HW, CG, SC, BL, RL, CD, SW and RW. Factors such as the sex of the lamb, birth type, and dam age significantly affected different morphological characteristics. Furthermore, BW was positively correlated with different morphological characteristics at different ages. On the other hand, equations were developed to predict BW at birth, weaning, and marketing based on various morphological characteristics while taking high into account.