Harrison Meredith A, Arce-Cordero Jose A, Seidel George E, Archibeque Shawn L, Whittier Jack C, Rhoades Ryan D, Ahola Jason K
Department of Animal Sciences, Colorado State University, Fort Collins, CO.
Department of Biomedical Sciences, Colorado State University, Fort Collins, CO.
Transl Anim Sci. 2020 Oct 27;4(4):txaa191. doi: 10.1093/tas/txaa191. eCollection 2020 Oct.
The All Heifer, No Cow (AHNC) beef production system is an alternative to conventional cow/calf production that involves insemination of nulliparous heifers with sexed semen to produce female calves that are early weaned at 3 mo of age. Dams are finished on a high-concentrate diet and harvested before reaching 30 mo of age. Objectives of this research were to document reproductive, feedyard, calf, and carcass performance of an AHNC herd; evaluate effects of carcass maturity on carcass quality; and determine if performance of initial cohorts (i.e., cohorts 1 and 2) differed from sustaining cohorts (i.e., cohorts 3-5). A total of 272 heifers were enrolled in the AHNC system via five annual cohorts. The system was initiated with 51 yearling, Angus-based heifers, and a replicate set ( = 56) was started 12 mo after. Heifers in cohorts 3 ( = 53), 4 ( = 56), and 5 ( = 56) were primarily offspring of prior cohorts (i.e., cohort 3 heifers born to cohort 1 females), but some were purchased to maintain inventory. Angus replacement heifers were purchased in cohorts 3 ( = 26), 4 ( = 26), and 5 ( = 28). Mean (±standard deviation) pregnancy rate at 30 d after fixed-time artificial insemination (AI) with sexed semen was 50.8% ± 9.4%, and 140-d pregnancy rate was 93.0% ± 1.5%. With AHNC, 61.0% ± 6.5% of females replaced themselves with a heifer. During finishing, average daily gain (ADG) was 1.9 ± 0.4 kg • d and dry matter intake (DMI) was 14.9 ± 1.9 kg • d. Hot carcass weight (HCW) was 367 ± 35 kg. The USDA grading system classified 20.5% of all carcasses ( = 220) as C maturity (A = 100, B = 200, etc.), 62.4% ± 29.1% of carcasses as USDA Choice. USDA yield grade (YG) was 2.6 ± 0.7. Based on cohorts 1 and 2, there were no differences ( = 0.96) in Warner-Bratzler shear force values between A and B maturity vs. C maturity carcasses. Across all cohorts, there were no differences in USDA YG, marbling score (MA), and lean maturity between A and B maturity vs. C maturity carcasses; there were differences in age ( < 0.001), bone maturity ( < 0.001), and overall maturity ( <0.001). A comparison of initial vs. sustaining cohorts showed that initial cohorts had lower ( < 0.001) DMI, heavier ( < 0.001) HCW, and more advanced ( < 0.05) bone maturity. However, there were no differences for 30- and 140-d pregnancy rates, ADG, USDA YG, and MA between initial and sustaining cohorts. The AHNC beef production system can effectively produce female calves and quality carcasses for harvest.
全小母牛、无母牛（AHNC）肉牛生产系统是传统母牛/犊牛生产方式的一种替代方案，该系统涉及用性别分选精液对未产小母牛进行授精，以生产在3月龄时提前断奶的雌性犊牛。母牛在高能量日粮饲养条件下育肥，并在30月龄前屠宰。本研究的目的是记录AHNC牛群的繁殖性能、育肥性能、犊牛性能和胴体性能；评估胴体成熟度对胴体品质的影响；并确定初始批次（即第1和第2批次）的性能是否与维持批次（即第3 - 5批次）不同。通过五个年度批次，共有272头小母牛进入AHNC系统。该系统最初有51头以安格斯牛为基础的一岁龄小母牛，12个月后开始另一组重复（n = 56）。第3批次（n = 53）、第4批次（n = 56）和第5批次（n = 56）的小母牛主要是前一批次的后代（即第3批次小母牛由第1批次母牛所生），但也购买了一些以维持存栏量。在第3批次（n = 26）、第4批次（n = 26）和第5批次（n = 28）购买了安格斯后备小母牛。使用性别分选精液进行定时人工授精（AI）后30天的平均（±标准差）妊娠率为50.8% ± 9.4%，140天妊娠率为93.0% ± 1.5%。采用AHNC系统，61.0% ± 6.5%的母牛能用一头小母牛替代自身。育肥期间，平均日增重（ADG）为1.9 ± 0.4 kg·d，干物质采食量（DMI）为14.9 ± 1.9 kg·d。热胴体重（HCW）为3S7 ± 35 kg。美国农业部分级系统将所有胴体（n = 220）的20.5%归类为C级成熟度（A = 100，B = 200等），62.4% ± 29.1%的胴体为美国农业部精选级。美国农业部产量等级（YG）为2.6 ± 0.7。基于第1和第2批次，A和B级成熟度与C级成熟度胴体之间的沃纳 - 布拉茨勒剪切力值无差异（P = 0.96）。在所有批次中，A和B级成熟度与C级成熟度胴体之间在美国农业部YG、大理石花纹评分（MA）和瘦肉成熟度方面无差异；在年龄（P < 0.001）、骨成熟度（P < 0.001）和整体成熟度（P < 0.001）方面存在差异。初始批次与维持批次的比较表明，初始批次的DMI较低（P < 0.001），HCW较重（P < 0.001），骨成熟度更高级（P < 0.05）。然而，初始批次和维持批次在30天和140天妊娠率、ADG、美国农业部YG和MA方面没有差异。AHNC肉牛生产系统能够有效地生产雌性犊牛和用于屠宰的优质胴体。
