Department of Animal Science, Texas A&M University, College Station, TX.
J Anim Sci. 2020 Jul 1;98(7). doi: 10.1093/jas/skaa189.
The objective of this study was to examine the differences in feeding behavior patterns of steers with divergent phenotypes for residual feed intake (RFI). Three trials were conducted with 508 Angus-based composite crossbred steers (body weight [BW] = 309 ± 57 kg) fed a high-concentrate diet in pens equipped with electronic feed bunks (GrowSafe System). Initial and final carcass ultrasound measurements (intra-muscular fat, backfat depth, and rib-eye area) were collected on days 0 and 70, and BW measured at 14-d intervals. Individual dry matter intake (DMI) and feeding behavior traits were collected for 70 d, and RFI calculated as the residual from the regression of DMI on average daily gain (ADG) and mid-test BW0.75. Steers were ranked by RFI and assigned to low-, medium-, and high-RFI classes based on ± 0.5 SD from the mean RFI within the trial. The feeding behavior traits evaluated in this study included frequency and duration of bunk visit (BV) and meal events, head-down (HD) duration, mean meal length, time-to-bunk interval, the maximum nonfeeding interval, and the day-to-day variation of these traits, defined as the root mean squared error (RMSE) from linear regression of each trait on the day of trial. Additionally, three ratio traits were evaluated: BV events per meal, HD duration per BV event, and HD duration per meal event. Low-RFI (feed-efficient) steers consumed 16% less (P < 0.01) DMI, while BW and ADG were not different compared with high-RFI steers. Low-RFI steers had 18% fewer and 21% shorter (P < 0.01) BV events, and 11% fewer and 13% shorter (P < 0.01) meal events per day compared with high-RFI steers. Furthermore, low-RFI steers exhibited less (P < 0.05) day-to-day variance in DMI, as well as in frequency and duration of BV and meal events and HD duration compared with high-RFI steers. Differences in feeding behavior traits due to RFI were minimally affected by covariate adjustment for DMI, indicating that steers with divergent RFI have distinct feeding behavior patterns that are largely independent of differences in DMI. These results suggest that feeding behavior traits may be useful biomarkers for the prediction of feed efficiency in beef cattle.
本研究旨在探究不同剩余采食量（RFI）表型的肉牛在采食行为模式上的差异。使用 508 头安格斯杂交牛（体重 [BW] = 309 ± 57 千克）进行了三项试验，这些牛在配备电子饲料槽（GrowSafe 系统）的畜栏中以高浓缩饲料饲养。在第 0 天和第 70 天采集初始和最终的 carcass 超声测量值（肌内脂肪、背膘厚度和肋眼面积），并在 14 天间隔测量 BW。在 70 天内收集个体干物质采食量（DMI）和采食行为特征，通过 DMI 对平均日增重（ADG）和中试 BW0.75 的回归计算 RFI。根据试验内平均 RFI 的 ± 0.5 SD 将牛分为低、中、高 RFI 类。本研究评估的采食行为特征包括槽访问（BV）和采食事件的频率和持续时间、低头（HD）持续时间、平均采食长度、槽间隔时间、最大非采食间隔时间以及这些特征的日变化，日变化通过每个特征对试验日的线性回归的均方根误差（RMSE）来定义。此外，还评估了三个比例特征：每采食事件的 BV 事件数、每 BV 事件的 HD 持续时间和每采食事件的 HD 持续时间。低 RFI（饲料效率高）的牛的 DMI 减少了 16%（P < 0.01），而 BW 和 ADG 与高 RFI 的牛没有差异。与高 RFI 的牛相比，低 RFI 的牛每天的 BV 事件减少了 18%，采食事件减少了 21%，每采食事件的 BV 事件减少了 11%，采食事件减少了 13%。此外，低 RFI 的牛的 DMI、BV 和采食事件的频率和持续时间以及 HD 持续时间的日变化较小（P < 0.05）。由于 RFI 导致的采食行为特征的差异在调整 DMI 后的协变量调整中影响较小，这表明具有不同 RFI 的牛具有明显不同的采食行为模式，这些模式在很大程度上独立于 DMI 的差异。这些结果表明，采食行为特征可能是预测肉牛饲料效率的有用生物标志物。
