Department of Animal Sciences, North Florida Research and Education Center, University of Florida, Marianna, FL 32446-7906, USA.
J Anim Sci. 2013 May;91(5):2254-63. doi: 10.2527/jas.2012-5242. Epub 2013 Mar 5.
Seventy-four beef heifers were used to evaluate relationships among performance, residual feed intake (RFI), and temperament measured as growing heifers (Phase 1) and subsequently as 3-yr-old lactating beef cows (Phase 2) in the same cohort. In both phases, females were housed in a covered facility and fed similar forage-based diets, and individual feed intakes, BW, BCS, chute scores (CS), exit velocities (EV), and pen scores (PS) were collected throughout the 70-d feeding trials. In Phase 2, cows were milked on trial d 14 (lactation d 28 ± 3.5) and trial d 70 (lactation d 84 ± 3.5) to determine energy-corrected milk (ECM) production. Ultrasonic backfat thickness (BF), and ribeye area (REA) were evaluated on d 0 and 70 of the trial in Phase 2. Heifers were ranked by RFI and placed into Low (<0.5 SD mean RFI; n = 27), Medium (within ± 0.5 SD; n = 23), and High (>0.5 SD mean RFI; n = 24) RFI groups. Body weight, BCS, and ADG were similar among all RFI groups; however, daily DMI differed for all groups (P < 0.01) and was greater (10.76 ± 0.24 kg/d) for High, intermediate (9.88 ± 0.25 kg/d) for Medium, and less (8.52 ± 0.23 kg/d) for Low RFI heifers. When cow performance was analyzed based on RFI rank as heifers, BW, BCS, ADG, RFI, d 14 and d 70 ECM, BF, and REA were similar among RFI groups; however, cows that were most efficient as heifers (Low) had decreased (P < 0.05) daily DMI values (10.30 ± 0.41 kg/d) compared with cows that ranked Medium (11.60 ± 0.44 kg/d) or High (11.50 ± 0.43 kg/d) as heifers. The Pearson rank correlation between Phase 1 and 2 RFI was r = 0.13 (P = 0.30), and Pearson rank correlations showed no relationship (P > 0.1) between RFI and temperament. Phase 1 CS was negatively associated with ADG in Phase 1 (r = -0.28; P = 0.02) and 2 (r = -0.32; P = 0.01), and positively associated with d 14 (r = 0.24; P = 0.04) and 70 (r = 0.25; P = 0.03) ECM. Phase 2 CS was negatively associated with Phase 2 ADG (r = -0.29; P = 0.01) and positively associated with d 14 (r = 0.46; P = 0.001) and 70 (r = 0.33; P = 0.004) ECM. Phase 2 PS also tended to be negatively associated with DMI in Phase 1 (r = -0.20; P = 0.096) and 2 (r = -0.20; P = 0.08). In this study, heifers that were most feed efficient subsequently consumed less feed as lactating cows and maintained similar performance. Feed efficiency was not associated with differences in temperament; however, more excitable females had poorer BW gains and tended to have reduced feed intakes but produced more ECM.
74 头肉牛后备牛用于评估生长阶段（第 1 阶段）和随后的 3 岁泌乳期（第 2 阶段）的性能、剩余采食量（RFI）和行为之间的关系，这些后备牛来自同一队列。在两个阶段中，雌性动物都被安置在一个有盖的设施中，并喂食类似的基于饲料的饮食，个体采食量、BW、BCS、滑道评分（CS）、出口速度（EV）和围栏评分（PS）在整个 70 天的喂养试验中进行收集。在第 2 阶段，奶牛在试验第 14 天（泌乳第 28 ± 3.5 天）和第 70 天（泌乳第 84 ± 3.5 天）挤奶，以确定能量校正乳（ECM）产量。在第 2 阶段的试验第 0 天和第 70 天评估了超声背膘厚度（BF）和肋眼面积（REA）。后备牛按 RFI 排名，并分为低（<0.5 SD 平均 RFI；n = 27）、中（± 0.5 SD 内；n = 23）和高（>0.5 SD 平均 RFI；n = 24）RFI 组。所有 RFI 组的体重、BCS 和 ADG 相似；然而，所有组的日 DMI 都不同（P < 0.01），高 RFI 组（10.76 ± 0.24 kg/d）、中 RFI 组（9.88 ± 0.25 kg/d）和低 RFI 组（8.52 ± 0.23 kg/d）的日 DMI 更高。当根据 RFI 排名分析奶牛的性能时，BW、BCS、ADG、RFI、第 14 天和第 70 天 ECM、BF 和 REA 在 RFI 组之间相似；然而，作为后备牛效率最高的奶牛（低 RFI）的日 DMI 值（10.30 ± 0.41 kg/d）比作为后备牛排名中等（11.60 ± 0.44 kg/d）或高（11.50 ± 0.43 kg/d）的奶牛降低（P < 0.05）。第 1 阶段和第 2 阶段 RFI 之间的 Pearson 秩相关系数为 r = 0.13（P = 0.30），Pearson 秩相关系数表明 RFI 与行为之间没有关系（P > 0.1）。第 1 阶段 CS 与第 1 阶段（r = -0.28；P = 0.02）和第 2 阶段（r = -0.32；P = 0.01）的 ADG 呈负相关，与第 14 天（r = 0.24；P = 0.04）和第 70 天（r = 0.25；P = 0.03）的 ECM 呈正相关。第 2 阶段 CS 与第 2 阶段 ADG 呈负相关（r = -0.29；P = 0.01），与第 14 天（r = 0.46；P = 0.001）和第 70 天（r = 0.33；P = 0.004）的 ECM 呈正相关。第 2 阶段 PS 也与第 1 阶段（r = -0.20；P = 0.096）和第 2 阶段（r = -0.20；P = 0.08）的 DMI 呈负相关趋势。在这项研究中，作为后备牛效率最高的牛随后作为泌乳牛消耗的饲料较少，但保持了相似的性能。饲料效率与行为差异无关；然而，更兴奋的雌性动物 BW 增长较慢，倾向于减少采食量，但产生更多的 ECM。
