The objective of this study was to evaluate the effects of residual feed intake (RFI) on reproductive competence of Hays Converter heifers. Twenty-one Hays Converter heifers were classified as more (low-RFI; n: 8, RFI ≤ - 0.6 kg dry matter DM/d), average (medium-RFI; n: 6, 0.3 ≤ RFI ≥ -0.5 kg DM/d), and less (high-RFI; n: 7, RFI ≥ 0.4 kg DM/d) feed efficient. Rumen temperature was continuously monitored every 10 minutes throughout the study using an automated smart rumen bolus system. Reproductive status was assessed by follicle count, ovulation occurrence, and measurement of the left uterine horn diameter. No differences in final body weight, average daily gain, feed conversion ratio, or dry matter intake were observed across RFI groups (P > 0.10). Rumen temperature showed significant hour × RFI (P = 0.0009) interaction, with high-RFI heifers having higher temperatures for several hours compared to more efficient groups. Reproductive traits did not differ by RFI, but follicle counts varied significantly over days (P < 0.05). In conclusion, RFI classification influenced rumen temperature patterns but did not affect reproductive competence or growth performance.
Silva et al. (Tue,) studied this question.