PDF(Pubmed)
Abstract：
Brangus cattle are gaining popularity in the Southeast U.S. due to the desirable heat tolerance from their Brahman influence combined with the superior carcass merit aspects of Angus genetics. However, little is known about the optimal evaluation conditions for this hybrid breed when placed on test for Residual Feed Intake (RFI), a heritable measure of feed efficiency that allows improvement in performance without altering carcass traits. To address this, dry matter intake (DMI) was measured on Brangus heifers for 70-d to determine the optimal days on feed required to estimate feed intake and ADG and assess if inclusion of ultrasound measures of carcass merit into the model impact RFI rankings for this breed. The 56-d test period had a regression coefficient of 0.96 (p < 0.0001), R2 = 0.94, rp = 0.97 (p < 0.0001), and rs = 0.97 (p < 0.0001), indicating little change in rank of cattle for DMI compared to a 70-d test. ADG was the limiting factor in determining test duration. Based upon examining only heifers that calved, ultrasound backfat measures should be included in the RFI model to normalize for differences in heifer maturity. Results from this study indicate that a test duration of 56-d is sufficient to accurately estimate DMI in this population. This data indicates on-test duration can be shortened, enhancing the rate of genetic change by reducing cost and increasing the number of animals that can be tested annually.
摘要：
由于婆罗门的影响以及安格斯遗传学的优良car体价值方面所带来的良好耐热性，布朗斯牛在美国东南部越来越受欢迎。然而,当进行残留饲料摄入量(RFI)测试时，对这种杂交品种的最佳评价条件知之甚少，饲料效率的可遗传度量，可以在不改变car体性状的情况下提高性能。为了解决这个问题，在Brangus小母牛上测量干物质摄入量（drymatteradvaction，简称di）70天，以确定估计采食量和ADG所需的最佳采食天数，并评估是否将car体价值的超声测量纳入该品种的模型影响RFI排名。56天测试周期的回归系数为0.96（p<0.0001），R2=0.94，rp=0.97（p<0.0001），rs=0.97（p<0.0001），表明与70天测试相比，在MDI的牛等级变化不大。ADG是确定测试持续时间的限制因素。根据只检查产牛的小母牛，RFI模型中应包括超声回脂测量，以标准化母牛成熟度的差异。这项研究的结果表明，56天的测试持续时间足以准确估计该人群中的QI。该数据表明测试持续时间可以缩短，通过降低成本和增加每年可以测试的动物数量来提高基因变化的速度。
