Genetic correlations between milk fatty acids grouped according to origin until 95 days in milk and fertility of Holstein cows in Japan

Abstract

Mitigating the effect of negative energy balance in early lactation is important for improving the fertility of dairy cows, and milk fatty acid (FA) composition may reflect energy status. We used insemination records and monthly test-day records to examine the genetic relationships between FAs grouped according to origin (FAOs) at early lactation and fertility traits in the first lactation of Japanese Holstein cows. The FAO traits we assessed were de novo FAs (C4:0 to C14:0) on a milk basis (DnM) and on a total FA basis (DnF) and preformed FAs (C15:0 and ≥ C17:0) on a total FA basis during 95 days in milk (DIM). The fertility traits evaluated were conception rate at first insemination (CR) and days open (DO). We applied a two-trait (each FAO and fertility trait) linear model to estimate the genetic correlations between them. The genetic correlations of DnM and DnF within 35 DIM with CR were 0.44 and 0.31, respectively, and those with DO were −0.27 and −0.26, respectively. These results suggest that genetic improvement in de novo FAs within 35 DIM could help to increase fertility in the first lactation.