Relationship between residual feed intake and female reproductive measurements in heifers sired by high–or low–residual feed intake Angus bulls1

Animals need to be feed efficient and reproductively sound for cow-calf producers to optimize profits. The objective of this study was to determine the relationship between feed efficiency and reproductive performance. Angus-based commercial cows were bred to Angus sires that had divergent residual feed intake (RFI) estimated breeding values published by the Angus Society of Australia. Data for this study included 136 crossbred females with multiple parity information. Feed-efficiency measures included RFI and daily DMI. The RFI was calculated by regressing actual feed intake on mid-test metabolic BW and ADG. Heifers were synchronized and mated by AI one time; natural-service sires followed. Pregnancy was determined approximately 60 d after the end of the breeding season. Reproductive measurements were pregnancy rate, first-service conception rate, calving percentage, and calving day. These data showed no relationship between pregnancy rate, first-service conception rate, calving rate, or calving date and phenotypic RFI or DMI (P > 0.10). Heifers that were sired by efficient RFI estimated breeding value bulls tended to have an improved calving rate in parity 2 (P < 0.10), but sire groups did not differ in pregnancy rate, first-service conception rate, or calving day (P > 0.10). This study showed no apparent unfavorable relationship between RFI and fertility as measured by pregnancy rate, first-service conception rate, calving rate, or calving day. Further research with larger numbers of females is needed to determine the relationships between feed efficiency and female reproduction. [PUBLICATION ABSTRACT]