Selection for Residual Feed Intake Will Not Unfavorably Impact Reproductive Performance in Dairy Cows

For residual feed intake (RFI) to be used as an alternative measure of feed efficiency, it must not have an unfavorable genetic relationship with fertility. Therefore, the objectives are to estimate heritability for RFI and reproductive parameters and determine the genetic relationship between RFI and reproductive traits in Holstein cows. Daily measurements of DMI, milk yield, weekly milk composition, and monthly body weight were used to calculate RFI on 1,513 Holstein cows at Virginia Tech and Iowa State University. Measures of reproductive performance included number of services (NS; n = 1,337), previous days dry (DD; n = 816), days open (DO; n = 860), and days to first calving (DFC; n = 572). Genetic correlations and heritability estimates were calculated in ASReml using a sire model. Random and fixed effects included herd, birth season, age, calving season, and dam. There were 190 unique sires with an average of 5 progeny per sire. As expected, heritability estimates were moderate (0.21 ± 0.07) for RFI and low for all reproductive traits (h² ≤ 0.09 ± 0.04). Genetic correlations suggest that selection for RFI will indirectly select for lower NS (r_g = 0.22 ± 0.17, P = 0.011) and DO (r_g = 0.21 ± 0.17, P = 0.010). No genetic relationship was detected for DD (r_g = 0.16 ± 0.17, P = 0.21) or DFC (r_g = -0.041 ± 0.13, P = 0.36). Overall, results suggest that selection for decreased RFI will not have an unfavorable impact on reproductive performance in dairy cows.