In the northeastern United States, pastures are predominantly cool-season perennial grasses and legumes that are dormant in the summer resulting in a decline in forage nutritive value and availability, commonly referred to as “summer slump.” Strategies to alleviate summer slump may include stocking management or supplementation with or without an ionophore such as monensin to maximize efficiency. A 3-yr study (n = 32 cow–calf pairs; 718.0 ± of 83.9 kg) was conducted to evaluate the effects of rotational (ROT) or continuous (CONT) stocking method with or without monensin on forage production, pasture nutritive value, and animal production. Continuous and ROT stocking treatments were assigned to eight 2.9-ha pastures with two replicates/year for 56 grazing days during the summer. Treatments were arranged as a 2 × 2 factorial, and supplements included with or without monensin (200 mg cow⁻¹ daily; Rumensin 90, Elanco Animal Health) delivered once daily (0.45 kg cow⁻¹). Disk meter height was maintained using put-and-take animals with four tester cow–calf pairs per pasture. Carrying capacity (CC) and calf average daily gain (ADG) were not influenced by stocking management. Rotational stocking increased cow body weight (BW) change by 6.6 kg. Monensin improved CC by 9% regardless of stocking method but did not affect cow BW change or calf ADG. Based on this study, monensin can improve carrying capacity and stocking rate regardless of stocking method. Implementing rotational stocking may improve pasture health by suppressing weed growth and enhancing forage nutritive value in pastures containing cool-season perennial forages.

中文翻译：

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放养方式和添加莫能菌素对奶牛和小牛生产性能和牧场生产力的影响

在美国东北部，牧场主要是凉爽季节的多年生草和豆类，它们在夏季处于休眠状态，导致草料的营养价值和可用性下降，通常被称为“夏季衰退”。缓解夏季低迷的策略可能包括放养管理或添加或不添加离子载体（如莫能菌素）以最大限度地提高效率。一项为期 3 年的研究（n = 32 对牛-小牛；进行了 718.0 ± 83.9 kg) 以评估使用或不使用莫能菌素的轮作 (ROT) 或连续 (CONT) 放养方法对牧草生产、牧草营养价值和动物生产的影响。连续和 ROT 放养处理被分配到八个 2.9 公顷的牧场，每年两次重复，在夏季放牧 56 天。处理被安排为 2 × 2 因子，包括或不包括莫能菌素的补充剂（每天 200 mg 牛^-1；Rumensin 90，Elanco Animal Health）每天一次（0.45 kg 牛^-1）。使用放养动物保持盘米高度，每个牧场有四对测试牛-小牛。承载能力 (CC) 和小牛平均日增重 (ADG) 不受放养管理的影响。轮养使奶牛体重（BW）变化增加了 6.6 公斤。无论放养方法如何，莫能菌素都能将 CC 提高 9%，但不影响奶牛体重变化或小牛 ADG。根据这项研究，无论采用何种放养方式，莫能菌素都能提高承载能力和放养率。实施轮牧可以通过抑制杂草生长和提高含有冷季多年生草料的草场的草料营养价值来改善草场健康。