GENETIC EVALUATION OF BIRTH AND WEANING WEIGHT OF GUDALI AND 2-BREED SYNTHETIC WAKWA BEEF-CATTLE POPULATIONS UNDER SELECTION IN CAMEROON - GENETIC AND PHENOTYPIC TRENDS

Breeding programmes for Wakwa and Ngaundere Gudali cattle breeds were initiated in Wakwa (Cameroon) in 1952 and 1965, respectively, to impro ve growth performance of the indigenous breeds. Animals were selected on 240-day weaning weight (WWT). Data analysed covered the period 1971 through 1985 and consisted of 2211 calf birth weight (BWT) and 1409 W WT records on Gudali and 1196 BWT and 763 WWT records on Wakwa. Select ion responses in BWT and WWT were estimated as regressions of average sire estimated transmitting abilities (ETAs) and average dam estimated breeding values (EBVs) on year of calving. ETAs and EBVs were predict ed using best linear unbiased prediction procedures. Estimated annual changes in sire ETAs for WWT were 0.67 (s.e. 0.1 7) and 1-69 (s.e. 1.1 3) kg/year for Gudali and Wakwa, respectively. Corresponding trends in dam EBVs were -0.03 (s.e. 0.03) and -0.24 (s.e. 0.19) kg/year. Estima ted correlated trends in BWT among Gudali and Wakwa sires were 0.09 (s .e. 0.05) and -0.14 (s.e. 0.04) kg/year, respectively. Corresponding c orrelated trends in BWT associated with dam selection were essentially zero, being -0.001 (s.e. 0.001) and -0.01 (s.e. 0.01) kg/year. Enviro nmental trends were negative for all traits except Gudali WWT. Phenoty pic trends were all positive, except that of Wakwa BWT. Overall, selec tion on WWT yielded moderate selection reponse despite substantial inf rastructural constraints in the breeding programme. Trends in sire ETA s and dam EBVs for WWT jointly accounted for estimated genetic gains o f 8.60 kg in Gudali and 20.4 kg in Wakwa over the study period. Overal l correlated response in BWT during the study period was significant ( P < 0.001) and negative for Wakwa. It was positive but not significant for Gudali.