This study evaluated the influence of cow age and temperature adjusted for wind chill (T_windchill) on supplement intake behavior of beef cattle winter grazing northern mixed grass prairie rangelands. A commercial herd of 272 (yr 1) and 302 (yr 2) bred cows (Angus, Simmental x Angus) ranging in age from 1- to 12-yr-old grazed a 329-ha rangeland pasture (~1.5 ha AUM^-1) from November to January. Cows were grouped into 7 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% crude protein 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 T_windchill × 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 T_windchill conditions in both years (P < 0.01). There was also negative linear effect of age on supplement intake (g ∙ kg of body weight^-1 ∙ d^-1) at average T_windchill in year 1 and below average T_windchill in year 2 (P < 0.01). Cow age had a quadratic effect on supplement intake for days with below average T_windchill in year 1 (P = 0.02), however, this was a curvilinear response where yearlings and 2-year-olds consumed more supplement per kg of body weight than other age cattle (P < 0.01). Cow age had positive linear effects on variation in supplement intake at below average T_windchill conditions in both years (P < 0.01). Daily visits to the supplement feeders displayed a T_windchill × cow age interaction (P < 0.01), where there was a linear decrease in visits with increasing age at below average T_windchill 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.

中文翻译：

---

年龄和环境条件对北方混交牧草牧场冬季放牧的肉牛补充饲料摄入量的影响。

这项研究评估了风寒（T _windchill）调整的奶牛年龄和温度对北部混合草草原草原上冬季放牧的肉牛补充摄入行为的影响。1至12岁的272头（第1年）和302头（第2年）的商业奶牛（安格斯，西门塔尔x安格斯）放牧了329公顷的牧场（〜1.5公顷AUM ^-1）从十一月到一月。母牛分为7个年龄段（1岁，2岁，3岁，4岁，5岁，6岁和≥7岁）老年人），并可以自由选择使用30％的粗蛋白自饲低芥酸菜籽粕为基础的颗粒状补品，其中含25％的盐以限制摄入。目标每日摄入量为0.91千克∙牛^-1 ∙d ^-1。在SmartFeed Pro自喂系统中提供了补充剂，以测量单个动物补充剂的摄入量和行为。在补充喂食器附近放置了一个发病HOBO U30-NRC气象站，以收集整个放牧期的天气数据。平均每天补充摄入和在补充摄入系数的变化显示为T_的Windchill ×牛年龄×年相互作用（P ≤0.02）。在两年中，T_风寒条件均低于平均水平的日子，年龄对补充摄入量（kg∙牛^-1 ∙d ^-1）的线性影响为负（P <0.01）。年龄对补充剂摄入也有负面线性影响（g∙kg体重^-1 ∙d^-1）在第一年的平均T_风冷和低于第二年的平均T_风冷（P <0.01）。奶牛的年龄对第1年的平均_风速低于平均T_风寒的几天的补充摄入量有二次影响（P = 0.02），但是，这是曲线反应，一岁和2岁的婴儿每公斤体重消耗的补充剂比其他多年龄的牛（P <0.01）。在低于平均T_风寒条件下，两年的奶牛年龄对补充摄入量的变化具有积极的线性影响（P <0.01）。每天对补充饲养者的访问显示出T_风寒×牛龄交互作用（P<0.01），在低于平均T_风冷条件下，访问次数随年龄增长呈线性下降（P <0.01）。总之，奶牛年龄和冬季环境条件相互影响，从而影响动物补品的摄入行为，并因此影响了冬季放牧肉牛的营养输送效率。