Crossbreeding, Additive And Heterotic Effects On Production Traits In Jersey Crossbred Cattle At Agricultural Research Station , Legon.

ABSTRACT Relative performance of breed groups, additive and heterotic effects on milk production, reproduction and calf growth traits in Jersey x West African Shorthorn (WAS) and Jersey x Sokoto Gudali (GUD) crossbred cattle were studied using sixteen years field records kept at the Agricultural Research Station, Legon. The genotypes consisted of WAS; 1/2 Jersey, 1/2 WAS (WAS Fj); 3/4 Jersey, 1/4 WAS (WAS Be); GUD; 1/2 Jersey, 1/2 GUD (GUD Fj) ; 3/4 Jersey, 1/4 GUD (GUD Be). Milk production traits analysed were first lactation milk yield, average lactation milk yield, average daily milk yield, annualized milk yield, lactation fat yield, fat percentage and lactation length. Analysis of reproduction traits included age at first calving, number of services per conception and calving interval. The calf growth traits examined were birthweight average daily gain to weaning and weaning weight. All traits were analysed by least sguares fixed model procedures using the GLM methods in SAS (1987) to generate genotypic least sguares means. Additive and heterotic effects on crossbreds were estimated using the additivedominance model. With regard to the milk production traits and calf growth traits, the performance of GUD was significantly (P < .01) better than WAS. WAS and GUD were similar for the reproductive traits except for calving interval where GUD had a significantly (P < .01) shorter calving interval than iiiWAS (475 days as against 551 days). WAS Fj and GUD Fj crossbreds were significantly (P < .05) better than their corresponding purebreds for all the traits examined except for birth weight where both Fj's were similar to their respective purebreeds. This indicated that crossbreeding with Jersey would lead to significant increases in the production level of the local breeds. GUD Be and GUD Fj cows were similar for the milk production traits whereas WAS Be cows were superior to WAS F1 cows. WAS Be calved significantly (P < .05) earlier for the first time (36 months) than WAS Fj (42.3 months). There was no difference between WAS Be and GUD Be when compared to their corresponding Fj' s for the other reproductive traits. WAS Be and GUD Be calves weighed significantly (P < .01) more at birth (21.7kg and 24.6kg respectively) than their respective Fj's (20.1 kg and 23.1 kg respectively). The performance of WAS Be and WAS FI were similar for preweaning average daily gain (ADG) and weaning wight. GUD Be declined significantly (P < .05) in growth rate when compared to GUD Fj. Additive genetic breed effects and heterosis contributed significantly to the improvement in milk production traits and calf growth traits in the WAS crossbred group. Additive effects however,- made greater contribution to the improvement than heterotic effects. Of the reproductive traits in WAS crossbred group, only the additive effect for ivage at first calving (-10.2 ± 2.5 months) and the heterotic effect for calving interval (-102 ± 31.8 days) were significant (P < .05) and desirable. These results showed that additive and heterotic effects could be exploited in crossbreeding to improve growth and milk production in WAS. Only average lactation milk yield and lactation length were significantly (P< .05) improved by additive effect among the milk production traits in the GUD crossbred group. Additive and heterotic effects were not significant for any of the reproductive traits in GUD crossbreds. Additive and heterotic effects however, significantly (P < .05) influenced calf growth traits in GUD crossbreds.