Abstract

Alternative management strategies with no cows and all heifers may improve biological and economic efficiency of beef production. The All Heifer, No Cow (AHNC) beef production system involves insemination of nulliparous heifers with female sex-selected semen (FSS) to produce primarily female calves that are early weaned at 3 mo of age. Dams are finished on a high concentrate diet and harvested before 30 mo of age. The objectives of this research were to: 1) build a dynamic model of an AHNC beef production system to quantify system biological and economic efficiency; 2) compare effects of utilizing FSS vs. conventional semen on biological and economic efficiency; 3) evaluate what-if scenarios to determine the effects on biological and economic efficiency of changing variables ±5%, 10%, 15%, and 20% from initial observed values; and 4) evaluate the effects on biological and economic efficiency of changing variables ±10% from initial observed values. A model was built over a 21-yr horizon using Stella Architect. Biological parameter values in the model were based on the 6 yr of data collected from the management of an AHNC demonstration herd. In the model animal, total digestible nutrients (TDN) intake, hot carcass weight (HCW), and age at harvest were randomized. Feed, animal, and carcass prices included in the model were based on 10 yr of historical U.S. price data. Key response variables were biological and economic efficiency (mean ± SD). Biological efficiency was defined as the ratio of output (kilograms of HCW produced) to input (lifetime kilograms of feed TDN consumed), and economic efficiency was measured using a benefit–cost ratio (BCR) and unit variable cost (UVC). Over 40 simulation runs, the predicted mean biological efficiency was 0.0714 ± 0.0008. Economic efficiency was 0.95 ± 0.02 and US $445.41 ± 0.06 for BCR and UVC, respectively. Biological and economic efficiency was improved in the conventional semen scenario; biological efficiency was 0.0738 ± 0.0008, and BCR and UVC were 0.99 ± 0.04 and US $407.24 ± 0.006, respectively. Under this parameterization and market conditions, the AHNC beef production system failed to achieve profitability under any scenario that was evaluated. However, this review did not account for the potential increased genetic benefit from a decreased generation interval and the reduction in feed energy in comparison to a conventional cow/calf system.

中文翻译：

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使用基于 6 年示范畜群数据的系统动力学模型评估全小母牛、非母牛牛肉生产系统的生物学和经济效率

摘要

没有奶牛和所有小母牛的替代管理策略可能会提高牛肉生产的生物和经济效率。All Heifer, No Cow ( AHNC ) 牛肉生产系统涉及用雌性选择的雌性精液 ( FSS)对未产小母牛进行授精) 主要生产 3 月龄早期断奶的雌性小牛。大坝以高精饲料喂养，并在 30 个月龄前收获。本研究的目标是：1) 建立一个 AHNC 牛肉生产系统的动态模型，以量化系统的生物和经济效率；2) 比较使用 FSS 与传统精液对生物和经济效率的影响；3) 评估假设情景，以确定与初始观测值相差 ±5%、10%、15% 和 20% 的变化变量对生物和经济效率的影响；和 4) 评估从初始观察值变化 ±10% 的变量对生物学和经济效率的影响。使用 Stella Architect 在 21 年的范围内构建了一个模型。模型中的生物参数值基于从 AHNC 示范畜群管理中收集的 6 年数据。在模型动物中，总可消化营养素（TDN ) 的摄入量、热胴体重 ( HCW ) 和收获时的年龄是随机的。模型中包含的饲料、动物和胴体价格基于 10 年的美国历史价格数据。关键响应变量是生物学和经济效率（平均值±标准差）。生物效率定义为产出（生产的 HCW 公斤数）与投入（终生消耗的饲料 TDN 公斤数）之比，经济效率使用效益成本比 ( BCR ) 和单位可变成本 ( UVC )来衡量）。超过 40 次模拟运行，预测的平均生物效率为 0.0714 ± 0.0008。BCR 和 UVC 的经济效益分别为 0.95 ± 0.02 和 US $445.41 ± 0.06。传统精液方案的生物和经济效率得到提高；生物效率为 0.0738 ± 0.0008，BCR 和 UVC 分别为 0.99 ± 0.04 和 US $407.24 ± 0.006。在这种参数化和市场条件下，AHNC 牛肉生产系统在任何评估的情况下都未能实现盈利。然而，与传统的母牛/小牛系统相比，本综述没有考虑到由于世代间隔缩短和饲料能量降低而带来的潜在增加的遗传益处。