Horton Lucas M, Depenbusch Brandon E, Holland Ben P, Word Alyssa B, Streeter Marshall N, Hutcheson John P, Renter David G
Center for Outcomes Research and Epidemiology and the Department of Diagnostic Medicine and Pathobiology, Kansas State University, Manhattan, KS 66506, USA.
Innovative Livestock Services, Inc., Great Bend, KS 67530, USA.
Transl Anim Sci. 2022 Dec 13;7(1):txac162. doi: 10.1093/tas/txac162. eCollection 2023 Jan.
Research objectives were to evaluate effects of two implant programs for beef heifers fed three different durations (days-on-feed; DOF) on carcass weight and composition (primary outcomes) and feedlot performance (secondary outcomes) at commercial feedlots. Data from a randomized trial in Kansas were analyzed separately and also pooled with data from two previously published trials conducted in Texas. Heifers were randomly allocated to pens within a block, and pens were randomized to treatments in a 2 × 3 factorial randomized complete block design. Implant programs were IH + 200 - an initial Revalor-IH implant [80 mg trenbolone acetate (TBA) and 8 mg estradiol (E)] and a re-implant after a mean of 98-d (± 10.8 SD) with Revalor-200 (200 mg TBA and 20 mg E), or XH - Revalor-XH, a single extended-release implant (200 mg TBA and 20 mg E). Heifers were fed to a baseline endpoint (BASE; pooled mean 166-d ± 11.9 SD), +21, or +42 additional DOF. A total of 10,583 crossbred heifers with mean initial body weight (BW) 315 kg (± 20.1 SD) were enrolled in 144 pens in 24 blocks (treatment replications) across the three trials. General and generalized linear mixed models accounting for clustering of trials, blocks, and pens were used to test for effects of treatments, with significance set at α = 0.05. The only implant program × DOF interaction in pooled analyses was for dry matter intake (DMI; < 0.01); IH + 200 heifers had lower mean DMI than XH when fed +42 DOF. Gain:feed was higher for IH + 200 compared to XH with dead and removed animals excluded ( < 0.01) or included ( = 0.03). For IH + 200, hot carcass weight (HCW) increased ( < 0.01), USDA Yield Grade (YG) distributions shifted towards lower numerical categories ( < 0.01), and Prime carcasses decreased while Select increased compared to XH ( < 0.01). For each incremental increase in DOF, final BW ( < 0.01) and HCW increased ( < 0.01), while daily gain ( < 0.01) and gain:feed ( < 0.01) decreased. Categories of YG were affected by DOF ( < 0.01); there were fewer YG 1 and 2 and more YG 4 and 5 carcasses for +42 compared to BASE and +21. USDA Quality Grade (QG) distributions differed by DOF ( < 0.01); each incremental increase in DOF resulted in more Prime and fewer Select carcasses. Without meaningful interactions, tested implant programs likely have a consistent effect when heifers are fed to similar DOF, while changes in HCW, QG, and YG may influence marketing decisions when extending DOF.
研究目标是评估两种植入方案对商业饲养场中采食三种不同天数（饲养天数；DOF）的肉用小母牛的胴体重量和组成（主要指标）以及饲养场性能（次要指标）的影响。对堪萨斯州一项随机试验的数据进行了单独分析，并与之前在德克萨斯州进行的两项已发表试验的数据进行了合并。小母牛在一个区组内随机分配到栏中，栏再按照2×3析因随机完全区组设计随机分配到各处理组。植入方案为IH + 200——最初植入Revalor - IH[80毫克醋酸群勃龙（TBA）和8毫克雌二醇（E）]，平均98天（±10.8标准差）后再植入Revalor - 200（200毫克TBA和20毫克E），或XH——Revalor - XH，一种单次缓释植入物（200毫克TBA和20毫克E）。小母牛被饲养至基线终点（BASE；合并均值166天±11.9标准差），再额外增加21天或42天的饲养天数。三项试验共有10583头平均初始体重（BW）为315千克（±20.1标准差）的杂交小母牛被纳入24个区组（处理重复）的144个栏中。采用考虑试验、区组和栏聚类的一般线性混合模型和广义线性混合模型来检验各处理的效果，显著性设定为α = 0.05。合并分析中唯一的植入方案×饲养天数交互作用是针对干物质采食量（DMI；P<0.01）；采食42天饲养天数时，IH + 200小母牛的平均DMI低于XH。排除（P<0.01）或纳入（P = 0.03）死亡和淘汰动物后，IH + 200的增重：饲料比高于XH。对于IH + 200，热胴体重（HCW）增加（P<0.01），美国农业部产量等级（YG）分布向较低数值类别偏移（P<0.01），与XH相比，特级胴体减少而精选级胴体增加（P<0.01）。饲养天数每增加一次，最终体重（P<0.01）和HCW增加（P<0.01），而日增重（P<0.01）和增重：饲料比（P<0.01）降低.YG类别受饲养天数影响（P<0.01）；与BASE和+21相比，42天饲养天数时YG 1和2级胴体减少，YG 4和5级胴体增加。美国农业部质量等级（QG）分布因饲养天数而异（P<0.01）；饲养天数每增加一次，特级胴体增多，精选级胴体减少。由于没有有意义的交互作用，当小母牛饲养至相似的饲养天数时，所测试的植入方案可能具有一致的效果，而延长饲养天数时HCW、QG和YG的变化可能会影响销售决策。
