Winter grazing at northern latitudes often exposes beef cattle to periods of severe cold, which increases energy expenditure to maintain homeothermy ( Webster, 1970, 1971 Young and Christopherson, 1974). 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. 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). Cow age had positive linear effects on variation in supplement intake at below average T windchill conditions in both years ( 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-yr-olds consumed more supplement per kilogram of BW than other age cattle ( P < 0.01). There was also negative linear effect of age on supplement intake (g kg of BWˉ 1 dˉ 1) at average T windchill in year 1 and below average T windchill in year 2 ( P < 0.01). There was a negative linear effect of age on supplement intake (kg cowˉ 1 dˉ 1) for days with below average T windchill conditions in both years ( P < 0.01).
Average daily supplement intake and the coefficient variation in supplement intake displayed a T windchill × cow age × year interaction ( P ≤ 0.02). An Onset HOBO U30-NRC Weather Station was placed near the supplement feeders to collect weather data for the entirety of the grazing period.
#BEEF ANIMAL AGE PRO#
Supplement was provided in a SmartFeed Pro self-feeder system to measure individual animal supplement intake and behavior. The target daily intake was 0.91 kg cowˉ 1 dˉ 1. 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. 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 monthˉ 1) from November to January. 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.