CROSSBREEDING JERSEY WITH GHANA SHORTHORN AND SOKOTO GUDALI CATTLE INA TROPICAL ENVIRONMENT - ADDITIVE AND HETEROTIC EFFECTS FOR MILK-PRODUCTION, REPRODUCTION AND CALF GROWTH TRAITS

Crossbreeding data involving Ghana Shorthorn, Sokoto Gudali and their Jersey F1s and backcrosses collected over a 16-year period were analys ed to estimate additive and heterotic effects for milk production, rep roduction and calf growth traits. Sokoto Gudali was significantly bett er than Ghana Shorthorn in all milk production traits. Calving interva l and annualized milk production were better in Gudali than in the Sho rthorn. The F1s had higher lactation milk yield, milked longer, produc ed their first calves earlier and had shorter dry periods and calving intervals than their corresponding purebreds. However, genotype was no t significant for number of services per conception. Both F1s had high er average daily gain and weaning weight than their corresponding pure breds. Sokoto Gudali backcross (Jersey X F1) was significantly (P < 0. 05) better than the F1 in lactation length. However, in Gudali crosses , there was no advantage in increasing the proportion of Jersey genes beyond 0-5 for milk production traits. Additive effects were significa ntly (at least P < 0.05) lower in the Shorthorn and the Gudali than in Jersey for milk production traits except proportion of butterfat. Het erosis estimates were significant (P < 0.01) for milk production trait s for the Shorthorn but not for the Gudali. Heterotic effects were lar ge and significant (at least P < 0.05) in improving annualized milk pr oduction in Shorthorn crosses, whilst none of the heterotic effects fo r reproductive traits was significant. At both 0 and 0.5 levels of Jer sey inheritance, the Gudali was superior (P < 0.01) to the Shorthorn i n birth weight, weaning weight and pre-weaning average daily gain. Het erotic effects for calf traits were positive and much larger in Gudali crosses than in Shorthorn crosses. In general, backcrosses were, at b est, similar to the F1s, implying that upgrading these indigenous bree ds beyond 0.5 European inheritance may not be desirable.