Department of Agricultural, Food and Nutritional Science, University of Alberta, Edmonton, Alberta, T6G 2P5, Canada.
J Anim Sci. 2011 Nov;89(11):3401-9. doi: 10.2527/jas.2011-3867. Epub 2011 Jun 3.
Data from a 3-yr feeding trial of crossbred steers (n = 331) were used to examine the relationship between feeding behavior traits and feed efficiency in steers fed grower and finisher diets, successively. There were 2 feeding periods each year whereby the steers were fed a grower diet in the first feeding period (P1) and a finisher diet in the second feeding period (P2). Each feeding period lasted for a minimum of 10 wk, ad libitum. In addition to feed intake, records on 3 measures of feeding behavior [feeding duration (FD), head-down time (HDT), and feeding frequency (FF)] were collected using the GrowSafe feeding system. Residual feed intake (RFI) was calculated by regression, after which the steers were classified as low (<0.5 SD), medium (±0.5 SD), or high (>0.5 SD) from the mean. The steers had greater (P < 0.001) FD, HDT, and FF when the grower diet was fed but greater feeding rate (FR) when the finisher diet was fed. Including the measures of feeding behavior as covariates to the feed intake prediction model containing ADG, metabolic midweight, and ultrasound backfat accounted for more variation in DMI than models that did not contain these additional parameters. The FD and HDT were significantly different (P < 0.05) among the RFI classes regardless of the feeding period, whereas no differences (P > 0.90) were found for FR among the RFI classes. For the growing period and finishing period, respectively, FD had phenotypic correlations with HDT (0.79, 0.83), FF (0.14, 0.55), DMI (0.38, 0.34), and FR (-0.34, -0.21). Heritability estimates in P1 and P2 for FD, HDT, and FF were 0.25 ± 0.16, 0.14 ± 0.11; 0.14 ± 0.15, 0.09 ± 0.10; and 0.56 ± 0.19, 0.59 ± 0.18, respectively. Genetic correlations between P1 and P2 were 0.91 ± 0.26, 0.93 ± 0.37, and 0.94 ± 0.11 for FD, HDT, and FF, respectively. The results suggest that it may be appropriate to include feeding behavior traits as covariates to indicate measure(s) of animal activity in the calculation of RFI. Feeding behavior phenotypes were greater during the grower-fed period than the finisher-fed period. During these feeding periods, efficient steers exhibited fewer FF, shorter FD, and shorter HDT than inefficient steers.
利用杂交肉牛（n = 331）的 3 年饲养试验数据，研究了生长育肥期和肥育后期连续饲养条件下，肉牛采食行为特征与饲料效率的关系。每年有 2 个饲养期，第一个饲养期（P1）饲喂生长育肥期饲料，第二个饲养期（P2）饲喂肥育后期饲料。每个饲养期至少持续 10 周，自由采食。除了采食量外，还使用 GrowSafe 饲养系统记录了 3 项采食行为测量值[采食持续时间（FD）、低头时间（HDT）和采食频率（FF）]。通过回归计算剩余采食量（RFI），然后根据平均值将肉牛分为低（<0.5 SD）、中（±0.5 SD）或高（>0.5 SD）。饲喂生长育肥期饲料时，肉牛的 FD、HDT 和 FF 更大（P < 0.001），但饲喂肥育后期饲料时的采食速度（FR）更大。在包含 ADG、代谢中重和超声背膘厚的采食量预测模型中加入采食行为测量值作为协变量，比不包含这些额外参数的模型能更好地解释 DMI 的变化。无论饲养期如何，RFI 等级间的 FD 和 HDT 差异显著（P < 0.05），但 RFI 等级间 FR 无差异（P > 0.90）。对于生长期和育肥期，FD 分别与 HDT（0.79、0.83）、FF（0.14、0.55）、DMI（0.38、0.34）和 FR（-0.34、-0.21）具有表型相关性。P1 和 P2 中 FD、HDT 和 FF 的遗传力估计值分别为 0.25 ± 0.16、0.14 ± 0.11；0.14 ± 0.15、0.09 ± 0.10；和 0.56 ± 0.19、0.59 ± 0.18。P1 和 P2 之间的遗传相关系数分别为 0.91 ± 0.26、0.93 ± 0.37 和 0.94 ± 0.11。结果表明，在计算 RFI 时，将采食行为特征作为协变量纳入，以指示动物活动的测量值可能是合适的。生长育肥期的采食行为表型大于肥育后期。在这些饲养期内，高效肉牛的 FF、FD 和 HDT 均低于低效肉牛。
