A novel use of high density SNP assays to optimize choice of different crossbred dairy cattle genotypes in smallholder systems in East Africa

We present use of SNP technologies to obtain for the first time, rapid, large-scale, in situ estimates of performance of crossbred cows in smallholder herds. Compared to historical approaches, our approach allowed optimum crossbreed choices to be determined more rapidly and without question about the relevance of the environment. High-density SNP assays were used to estimate breed composition for a monitored population comprising 1292 cows from 610 smallholder farms in Kenya. The achieved milk yields are much lower than generally assumed and lactation curves are very flat out to 400 days. In poor production environments, lower grade crosses (containing <60% exotic dairy alleles) had the same yield as high grade crosses. Allowing for the larger size and maintenance requirements of high grade exotics, lower grade exotics will be the most economically productive animals in these environments

Use of high density SNP genotypes to determine the breed composition of cross bred dairy cattle in smallholder farms: Assessment of reproductive and health performance

Reproductive performance and disease data were recorded for 2 years on 1,824 dairy cows in smallholder farms using participatory approaches and onfarm recording. Most animals experienced one service to conception. Calving intervals were long, ranging between 261 and 761 days, with an average of 451±101days. Herd level of production (HeL) had significant effect on calving interval. However, there was no difference between crossbreds with different levels of exotic breed percentage or in different HeL classes in disease incidence. Most animals had less than 2 treatment events, despite the high disease burden in the study areas. Mortality rates were low, ranging from 2.13% to 2.65%. Even though the crossbred animals had higher performance compared to indigenous animals, the gains obtained were below what would be possible with better management. These results suggest that crosses with low exotic proportions would be the most optimal for the production systems studied