DAIRY-CATTLE CROSSBREEDING IN THE TROPICS - THE IMPORTANCE OF GENOTYPE X ENVIRONMENT INTERACTION

Reports on dairy cattle crossbreeding projects in the tropics were reviewed and results on milk yields were used to study the importance of the interaction between genotype and environment. The projects covered a wide variety of tropical environments, with production levels ranging from about 1000 kg to more than 3000 kg of milk per lactation. Two kinds of genetic contrasts were considered, namely F1 crosses of native cattle and a European breed vs. backcrosses to the same European breed (i.e. 50% vs. 75% exotic inheritance), and Jersey vs. Friesian crosses. F1 and backcrosses had on average similar milk yields. The correlation between the means of the two groups (across projects) was estimated at about 0.9. The hypothesis that animals with the higher proportion of exotic inheritance would perform relatively better under good than under poor conditions was not confirmed. Jersey crosses (F1) produced on average about 20% less milk than Friesian crosses (but perhaps not less milk fat). The relative performance of the two groups was independent of production level in the project. It was concluded that the data reviewed give no evidence of genotype × environment interaction across the range of genotypes and environments considered. © 1990.