Genetic and non-genetic factors affecting the performance of West African Dwarf (WAD), Yankasa (YAN) and WAD X YAN lambs in the tropics

Abstract

Genetic and non-genetic factors affecting performance of sheep at the Teaching and Research farm of the Federal University of Technology, Akure, Ondo State, Nigeria were studied from 2005-2006. Genetic groups involved were 8 West African Dwarf sheep (WAD), 10 Yankasa (YAN) and 10 WAD X YAN (XBD). Data were analysed using General Linear Model of least squares analysis of variance to test the influence of genetic group, sex, season and age on weights and linear body measurements such as height at withers (HT), body length (BL), Neck length (NL), Neck circumference (NC), heart girth (HG), Foreleg length (FL), Hind leg length (HL), Face length (FA), Ear length (EA), Headwidth (HW), shoulder width (SW), tail length (TL) and Rump height (RH). Weight, HT, BL, HG, FL, HL, FL, EL, TL and RH were significantly affected by genetic group. Female lambs weighed 0.75kg more than the males (p<0.01). Season of birth had significant effect on WT (p<0.0001), HT (p<0.01), NL (p<0.001), FL (p<0.0001), HL (p<0.0.0001), FA (p<0.01), SW (p<0.01) and RL (p<0.05), the traits were superior in the rainy season. Age significantly affected all parameters considered. The WAD (0.53) and XBD (1.39kg) lambs were and heavier during the rainy season as compared to the dry season. Of the body dimensional traits, HG had the highest correlation coefficients with WT in WAD and YAN lambs estimated at 0.86 and 0.89 respectively, whereas HT was the most correlated trait with WT in XBD lambs. Height at withers and body length were the most important additional variables to heartgirth accounting for 87% prediction of body weight in WAD and YAN lambs, whereas, HT, BL, NC, HG, SW, TL and RH could account for up to 90% of body weight in XBD lambs