Genomic prediction of crossbred dairy cattle in Tanzania: A route to productivity gains in smallholder dairy systems

Selection based on genomic predictions has become the method of choice for genetic improvement in dairy cattle. This offers huge opportunity for developing countries with little or no pedigree data, and prelimi-nary studies have shown promising results. The African Dairy Genetic Gains (ADGG) project initiated a digi-tal system of dairy performance data collection, accom-panied by genotyping in Tanzania in 2016. Currently, ADGG has the largest body of dairy performance data generated in East Africa from a smallholder dairy sys-tem. This study examines the use of genomic best lin -ear unbiased prediction (GBLUP) and single-step (ss) GBLUP for the estimation of genetic parameters and accuracy of genomic prediction for daily milk yield and body weight in Tanzania. The estimates of heritability for daily milk yield from GBLUP and ssGBLUP were essentially the same, at 0.12 +/- 0.03. The heritability estimates for daily milk yield averaged over the whole lactation from random regression model (RRM) GB-LUP or ssGBLUP were 0.22 and 0.24, respectively. The heritability of body weight from GBLUP was 0.24 +/- 04 but was 0.22 +/- 04 from the ssGBLUP analysis. Accuracy of genomic prediction for milk yield from a forward validation was 0.57 for GBLUP based on fixed regression model or 0.55 from an RRM. Corresponding estimates from ssGBLUP were 0.59 and 0.53, respec-tively. Accuracy for body weight, however, was much higher at 0.83 from GBLUP and 0.77 for ssGBLUP. The moderate to high levels of accuracy of genomic prediction (0.53-0.83) obtained for milk yield and body weight indicate that selection on the basis of genomic prediction is feasible in smallholder dairy systems and most probably the only initial possible pathway to implementing sustained genetic improvement programs in such systems.

Automated summary

Selection based on genomic predictions is feasible for genetic improvement in smallholder dairy systems in Tanzania, with moderate to high levels of accuracy (0.53-0.83) obtained for genomic prediction of daily milk yield and body weight. This approach is likely to be the only initial possible pathway to implementing sustained genetic improvement programs in such systems.