Healthier cows through genomics

Dairy cows are vulnerable to a number of pathogens commonly found on farms, which can reduce the animals’ fertility and lifespan and encourage a high reliance on the use of antibiotics. This situation was addressed by the INNATELYBETTERCOWS (A genomics approach to increasing disease resistance in dairy cows through improvements in innate immunity) project.

Project Partners hypothesized that genetic selection for high yielding dairy cows was associated with reduced innate responses, predisposing cows to common diseases such as mastitis and endometritis. EU and Chinese researchers reversed this trend by identifying key genes involved in innate immune function that can be activated by a wide range of pathogens.

Genome wide association studies were carried out using data from UK and Chinese Holstein-Friesian cows. Genotypes were analysed using somatic cell count (SCC) as an indicator trait for mastitis in both populations and compared with general health data. The results highlighted regions of association of SCC with single nucleotide polymorphism (SNP), a DNA sequence variation in Chromosomes 1, 4 and 21.

Scientists sequenced 15 candidate genes, confirming the presence of 52 SNPs in our populations of British and Chinese Holstein cows. DNA from the population of UK cows was genotyped with respect to 12 of these SNPs and the associations between genotype and SCC, health and survival data were analysed. Results revealed that several of the SNP were indeed associated with both disease and survival time within the herd.

The data obtained support the initial hypothesis that differences in genotype for candidate genes with important roles in the innate immune system do influence both the health and survival of Holstein dairy cows through altered susceptibility to a variety of diseases. Key pathways identified involve both the migration of immune cells into affected tissues and their ability to kill bacteria on arrival. This information can be used to improve selection of animals for breeding.

INNATELYBETTERCOWS will improve selection of animals for breeding, benefit future generations of cows through improved health and reduce antibiotic use in the dairy industry. It will also help to minimise the numbers of animals required to maintain milk production, thereby reducing the impact of dairy farming on the environment.