Winter Grazing Activity and Forage Intake of Range Cows in the Northern Great Plains

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Abstract
Two winter grazing trials were conducted with beef cows on native rangeland. The effects of winter weather variables on grazing activity and forage intake were determined. The minimum daily temperature (MDT) ranged from about 0 to −35 C during both trials. Cows grazed on native rangeland and consumed only forage that was readily available for the duration of the trials. In each trial, cows were fitted with 8-d vibration recorders to monitor grazing time. In the first trial, grazing time was monitored continuously from December 9, 1981 to January 14, 1982. Minimum and maximum time spent grazing by individual cows was .5 and 11.6 h/d, respectively. Grazing time was affected by cow age, presence of snow cover on the range, wind velocity and MDT. As MDT decreased, reduction in daily grazing time and grazing time during each of four 6-h time periods of the day were recorded. The simple correlation between MDT and daily grazing time was .60 (P<.01). In the second trial, forage intake was determined for five 5-d periods using lignin and chromic oxide as fecal markers and grazing time was monitored continuously from November 16, 1983 to December 30, 1983. As in the first trial, there was a linear effect of MDT on grazing time. Unlike trial 1, grazing was not affected by cow age. Forage intake was reduced at colder MDT. We concluded that adverse winter weather reduced grazing activity and forage intake of cows grazing on native rangelands. Copyright © 1986. American Society of Animal Science . Copyright 1986 by American Society of Animal Science

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