Genetic evaluation of birth and weaning weight of Gudali and two-breed synthetic Wakwa beef cattle populations under selection in Cameroon: genetic and phenotypic trends

Abstract

Breeding programmes for Wakwa and Ngaundere Gudali cattle breeds were initiated in Wakwa (Cameroon) in 1952 and 1965, respectively, to improve 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 WWT records on Gudali and 1196 BWT and 763 WWT records on Wakwa. Selection 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 predicted using best linear unbiased prediction procedures. Estimated annual changes in sire ETAs for WWT were 0·67 (s.e. 0·17) and 1·69 (s.e. 1·13) 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. Estimated 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 correlated 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. Environmental trends were negative for all traits except Gudali WWT. Phenotypic trends were all positive, except that of Wakwa BWT. Overall, selection on WWT yielded moderate selection reponse despite substantial infrastructural constraints in the breeding programme. Trends in sire ETAs and dam EBVs for WWT jointly accounted for estimated genetic gains of 8·60 kg in Gudali and 20·4 kg in Wakwa over the study period. Overall 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.

Estimates of genetic and environmental trends of growth traits in Boran cattle

“…A longer GI than that found in this study was reported for Gir cattle (8.02 years) in Brazil (Q ueiroz and L ôbo 1993) and for Wakwa cattle (8.67 years) in Cameroon (T awah et al 1994). However, this is still relatively long when compared with the overall average of 4.36 years (M rode 1988) from several beef cattle selection experiments, though this is largely from temperate breeds.…”

“…In both reports, a higher level of gain was reported in a single generation of selection than in the present study. T awah et al (1994) also reported annual changes in the sire‐estimated transmitting ability of 0.67 and 1.69 kg per year for WW in Gudali (African zebu) and Wakwa (a synthetic breed between Gudali and Brahman), respectively, in Cameroon.…”

“…Monitoring of genetic and environmental trends is crucial in tropical areas, where the annual variation in climatic conditions, particularly rainfall, is high. However, there is little published information on this status of selection schemes in tropical areas (B urrow et al 1991; T awah et al 1994).…”

Genetic Modification of Animals: Potential benefits and concerns

“…Results from IRAD Wakwa Centre (Fig. 3) show how during a 17 year period selection (conventional genetic modification) modified the genetic structure of Gudali beef cattle population (Ebangi et al, 2002) with long generation intervals (7-8 years) (Tawah et al, 1994). The target trait was growth (increased beef production).…”

Amélioration génétique bovine par voie de croisement et de sélection en Afrique Tropicale : Expériences du Cameroun

“…Héritabilités et corrélations génétiques directes et maternelles des performances de croissance chez le Goudali et le Wakwa Pn: Poids à la naissance, GMQ: Gain moyen quotidien, PS: Poids au sevrage, Pa: Poids annuel, P 18 : Poids à 18 mois, h A : Héritabilité directe, h M : Héritabilité maternelle, h T : Héritabilité totale, C 2 : Variance permanente environnementale maternelle, C AM : Covariance maternelle directe, r AM : Corrélation génétique entre les effets génétiques et maternels Ebangi et al (2001)obtenu durant la période de l'expérience est de 8,60 kg et 20,40 kg, respectivement, chez le zébu Goudali (variété Ngaoundéré) et la race synthétique Wakwa(Tawah et al, 1994). Cependant, les corrélations génétiques négatives entre les effets directs et maternels montrent que le progrès génétique serait davantage plus important si la sélection était concentrée sur les performances directes et maternelles(Tawah et al, 1994 ;Ebangi et al, 2001).Lhoste (1975) (%) : Pourcentage de réussite de l'insémination artificielle Lhoste (1975) estime que les faibles taux de réussite de l'insémination artificielle du Tableau 8 sont liés aux avaries subies par les semences. Il précise que la première avarie intervenue en 1969 était dûe à une déficience du récipient cryogénique, et la deuxième dûe à la détérioration du récipient destiné au transport d'azote.…”