Northern Agricultural Research Center, Montana State University, Havre, MT.
Department of Animal and Range Sciences, Montana State University, Bozeman, MT.
J Anim Sci. 2020 Jul 1;98(7). doi: 10.1093/jas/skaa217.
This study evaluated the influence of cow age and temperature adjusted for wind chill (Twindchill) on supplement intake behavior of beef cattle winter grazing northern mixed grass prairie rangelands. A commercial herd of 272 (year 1) and 302 (year 2) bred cows (Angus, Simmental × Angus) ranging in age from 1- to 12-yr-old grazed a 329-ha rangeland pasture (~1.5 ha animal unit month- 1) from November to January. Cows were grouped into seven age classes (1 yr old, 2 yr old, 3 yr old, 4 yr old, 5 yr old, 6 yr old, and ≥ 7 yr old) and were provided free-choice access to a 30% CP self-fed canola meal-based pelleted supplement with 25% salt to limit intake. The target daily intake was 0.91 kg cow- 1 d- 1. Supplement was provided in a SmartFeed Pro self-feeder system to measure individual animal supplement intake and behavior. An Onset HOBO U30-NRC Weather Station was placed near the supplement feeders to collect weather data for the entirety of the grazing period. Average daily supplement intake and the coefficient variation in supplement intake displayed a Twindchill × cow age × year interaction (P ≤ 0.02). There was a negative linear effect of age on supplement intake (kg cow- 1 d- 1) for days with below average Twindchill conditions in both years (P < 0.01). There was also negative linear effect of age on supplement intake (g kg of BW- 1 d- 1) at average Twindchill in year 1 and below average Twindchill in year 2 (P < 0.01). Cow age had a quadratic effect on supplement intake for days with below average Twindchill in year 1 (P = 0.02); however, this was a curvilinear response where yearlings and 2-yr-olds consumed more supplement per kilogram of BW than other age cattle (P < 0.01). Cow age had positive linear effects on variation in supplement intake at below average Twindchill conditions in both years (P < 0.01). Daily visits to the supplement feeders displayed a Twindchill × cow age interaction (P < 0.01), where there was a linear decrease in visits with increasing age at below average Twindchill conditions (P < 0.01). In summary, both cow age and the winter environmental conditions interacted to influence animal supplement intake behavior and, as a result, nutrient delivery efficacy in winter grazing beef cattle.
本研究评估了奶牛年龄和风寒调整温度（Twindchill）对北方混合草草原牧场冬季放牧肉牛补充摄入行为的影响。一个由 272 头（第 1 年）和 302 头（第 2 年）繁殖奶牛（安格斯、西门塔尔×安格斯）组成的商业牛群，年龄从 1 岁到 12 岁，从 11 月到 1 月在 329 公顷的牧场（~1.5 公顷动物单位月-1）放牧。牛被分为七个年龄组（1 岁、2 岁、3 岁、4 岁、5 岁、6 岁和≥7 岁），并自由采食含有 25%盐的 30%CP 菜籽油基颗粒补充料，以限制摄入量。目标日摄入量为 0.91 公斤牛-1 天-1。补充料在 SmartFeed Pro 自动喂食系统中提供，以测量个体动物的补充料摄入量和行为。在补充料喂食器附近放置了一个 Onset HOBO U30-NRC 气象站，以收集整个放牧期的天气数据。平均每日补充摄入量和补充摄入量的变异系数显示出 Twindchill×牛年龄×年份的相互作用（P≤0.02）。在两年中，当风寒条件低于平均水平时，年龄对补充摄入量（kg 牛-1 天-1）有负线性影响（P<0.01）。在平均 Twindchill 条件下的 1 年和低于平均 Twindchill 条件下的 2 年，年龄对补充摄入量（g/kg BW-1 天-1）也有负线性影响（P<0.01）。牛的年龄对低于平均 Twindchill 条件下的天数的补充摄入量有二次效应（P=0.02）；然而，这是一个曲线反应，1 岁和 2 岁的牛每公斤 BW 消耗的补充料比其他年龄的牛多（P<0.01）。在两年中，在低于平均 Twindchill 条件下，牛的年龄对补充摄入量的变异有正线性影响（P<0.01）。在低于平均 Twindchill 条件下，每日访问补充料喂食器显示出 Twindchill×牛年龄的相互作用（P<0.01），随着年龄的增加，访问量呈线性下降（P<0.01）。总之，奶牛年龄和冬季环境条件相互作用，影响冬季放牧肉牛的动物补充摄入量行为和养分输送效率。
