استفاده از مصرف خوراکی باقی مانده به عنوان معیار انتخاب بر عملکرد و هزینه های نسبی توسعه تلیسه های جایگزین گوشت گاو

Two heifers groups differing in residual feed intake (RFI) were compared with a third control (CON; n = 20) group of randomly selected heifers for performance, reproductive efficiency, and system economics to first calving and repeatability of RFI ranking, with all 3 groups selected from the same cohort. Following weaning, 70 Angus heifers (initial BW = 260 ± 3 kg; 6 mo of age) from a single cohort were fed a forage-based diet (10.0% CP; 65.2% TDN) for 93 d (period 1) where BW, DMI, ADG, G:F, and RFI were evaluated. After period 1 RFI testing, 40 heifers were classified into 2 groups [20 efficient heifers (low RFI; RFI = −1.01 ± 0.10 kg/d) and 20 inefficient heifers (high RFI; RFI = 0.77 ± 0.08 kg/d)] and then selected for a second feeding trial (period 2) and compared with the 20 CON heifers. All 60 heifers in period 2 (BW = 322 ± 2.9 kg; 10 mo of age) were fed for 93 d on a similar forage-based diet (11.0% CP; 66.5% TDN). Low-RFI heifers had the lowest (P = 0.01) RFI value of −0.33 kg/d, followed by CON and high-RFI heifers, −0.09 and 0.42 kg/d, respectively. Control heifers tended (P = 0.08) to have lower ADG (0.83 kg/d) compared with low-RFI (0.92 kg/d) or high-RFI heifers (0.91 kg/d), and low-RFI heifers tended (P = 0.08) to have greater G:F (0.10 ± 0.003) than either CON (0.9 ± 0.003) or high-RFI heifers (0.09 ± 0.003). Spearman rank correlation for RFI between period 1 and 2 was 0.58 (P < 0.01); however, 51% of heifers had a different RFI value in period 2 compared with period 1. First-calf pregnancy rates were 80% for low RFI, 93% for CON, and 100% for high RFI (χ2; P = 0.09). Winter feed costs were ~Can$25 per heifer lower for low-RFI heifers compared with high-RFI animals. Heifers with increased feed efficiency may exhibit reduced reproductive performance, suggesting further research is needed.