Improving dairy cow fertility using milk-based indicator traits

Improvement of dairy cow fertility by means of genetic selection has become increasingly important over the last decades. Because fertility traits are difficult to measure and have low heritabilities, indicator traits are of interest to supplement the prediction of genetic merit for female fertility. This paper examines milk-based traits that could be potential predictor of fertility: changes in protein and fat composition, fat to protein ratio, urea, lactose, ketone bodies, and mid-infrared prediction of body energy traits. The pattern of genetic correlations between these traits and fertility over days in milk is likely related to the cow’s energy balance state. Furthermore, changes in milk fatty acid profile were demonstrated as good potential predictors of fertility. Finally, additional research is warranted to investigate the association over the lactation between fertility and changes in milk biomarkers, potentially predicted by mid-infrared analysis of milk.