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Abstract Genetic selection focused on feed efficiency may prove to be valuable in reducing feed consumption costs and animal maintenance requirements without compromising growth. The Vytelle Sense system allows measurement of individual lamb DMI and varying feeding behaviors to identify feed efficient lambs. The aim of this study was to evaluate the impact of sire selection based on fecal egg count estimated breeding value (FEC EBV) on residual feed intake (RFI), gain:feed (G:F), and daily DMI. Katahdin ewes at the Virginia Tech Southwest Virginia Agricultural and Research Center (SWAREC) were mated to Katahdin rams (LowFEC: n = 4; HighFEC: n = 4) to divergently select for FEC EBV in their offspring (LowFEC: n = 36; HighFEC: n = 32). Post-weaning, lambs were fed a complete pellet (14% CP, 76% TDN) ad libitum in the Vytelle Sense system for 58 days. RFI was calculated as the difference between actual and expected DMI. DMI was predicted based on ADG and metabolic body size. Feeding duration per meal and DMI per meal were analyzed to determine feeding behavior. Statistical analyses were performed using PROC Mixed SAS (SAS Institute, Cary, NC). Sire FEC EBV type tended to have an effect on RFI (P = 0.06). Individual sire had a significant effect on RFI, G:F, and daily DMI (P 0.05). Sex did not impact RFI (P 0.10). Ram lambs had greater G:F values compared with ewes (0.32 vs. 0.26 kg; P 0.05). Rams had greater daily DMI compared with ewes (2.37 vs. 1.89 kg/d; P 0.05). Significance was detected between sires for meal duration (P 0.05). Ewe lambs exhibited greater meal duration compared with rams (237.3 vs. 203.4 s/meal; P 0.05). However, ewes had reduced DMI per meal compared with rams (0.29 vs. 0.34 kg/meal; P 0.05). Individual sire did not have an effect on meal DMI (P 0.10). To evaluate sire impact on RFI across multiple locations, LowFEC Katahdin rams (n = 2), mentioned previously, were bred to Katahdin ewes at the NC State University Upper Piedmont Research Station (UPRS) and the SWAREC. Genetic connectedness between locations allowed for comparisons of progeny performance. Post-weaning, UPRS lambs were fed a complete pellet (16% CP, 75% TDN) ad libitum in the Vytelle sense system for 45 d. Location did not impact RFI prediction for either sire (P 0.10). Variation between sires indicates potential sire impact on progeny feed efficiency and feeding behavior. Further studies are needed to evaluate sire RFI trends across multiple locations.
Valliere et al. (Fri,) studied this question.