Genomic Evaluation for Feed Advantage – Towards Feed Efficient Cows in UK Dairy Cattle

Abstract

The inclusion of feed efficiency into the UK national dairy selection index contributes to reduced environmental footprint of the dairy industry and provides additional profit to dairy farmers. Feed Advantage breeding values were introduced into UK dairy cattle genomic evaluations in August 2021. Genomic breeding values (GEBV) for Feed Advantage represents the kilograms (kg) of feed saved due to better feed efficiency and lower maintenance feed costs per lactation. Feed Advantage breeding value combines GEBV of wasted feed (WF) derived as deviation of predictions for dry matter intake (DMI) from production and maintenance, and feed saved due to maintenance using predictions for maintenance and current £PLI weight for maintenance in the UK national index. To obtain GEBV for DMI, a total of 174,379 weekly average DMI records (kg/d) from around 750,000 daily DMI records were included for 4,662 lactations of 1,888 Holstein dairy cows (in Lactation 1 to 4) from the UK Langhill research herd. The 80K imputed genotypes (79,051 SNP markers) were available for 4,356 genotyped animals including 1,702 genotyped cows in the Langhill herd, 1,689 active bulls in the UK, and an extra 965 genotyped bull ancestors in the pedigree of genotyped animals. Heritability for DMI was 0.18, averaged across lactations (Lactation 1, 2, 3+). The DMI between lactations is highly genetically correlated (lactation 2 and 3+ is correlated by 0.99, lactation 1 and 2+ is correlated by 0.91). Genomic breeding values (GEBV) for DMI were then estimated using single-step GBLUP method with an animal repeatability model using DMI data across lactations. Validations were carried out to assess prediction accuracy for DMI by setting up reference and validation populations considering three scenarios (i.e., forward prediction, prediction between genetic lines, and prediction between feeding groups). In summary, the prediction accuracy for DMI in forward prediction, prediction between genetic lines, and prediction between feeding groups were 0.62, 0.34, and 0.68, respectively. The GEBV for wasted feed (WF) was derived as deviation of GEBV for DMI from GEBVs for production and maintenance. The final publication of Feed Advantage breeding value combines GEBV for WF and feed saved due to maintenance using prediction for maintenance and current £PLI weight for maintenance in the UK national index. Current findings show promising results of genomic predictions on Feed Advantage in bringing additional profit to dairy farmers without sacrificing cows’ health and fertility, and in reducing environmental footprint of the dairy industry.