ABSTRACT
Summary A series of trials was conducted in 1977 to determine the effect of level of grazing pressure on organic-matter intake and the relationship between intake and forage disappearance. Levels of grazing pressure studied were 10, 20, 40, and 50 kg forage allowed/animal unit/day (kg/AU/day) for 14-day trials in April, July, and September. A standing crop of forage was measured before, in the middle of, and immediately after each trial. Organic-matter intake was estimated by the fecal output: indigestibility ratio technique. Organic-matter intake was highest in April; cattle also consumed more forage in September than in July. The combination of forage quality and animal physiological status explained the changes in intake by trial. Cattle consumed approximately 12 g/kg body weight0.75 less organic matter by the end of a trial than at the beginning. A trend was exhibited for cattle under the 10 and 20 kg/AU/day treatments to consume less forage by the end of trials than at the beginning of a trial. Total standing crop declined steadily during the grazing trials, with forage availability being significantly less at the end than at the beginning or middle of the trials. Averaged over the three trials, forage losses/AU/day were 8.5, 12.0, 12.7, and 16.3 kg for the 10, 20, 40, and 50 kg/AU/day grazing pressures, respectively. However, daily intake averaged across all treatments, periods, and trials was approximately 9 kg/AU/day. At the grazing-pressure level of 10 kg/AU/day, forage disappearance approximated the average daily intake, whereas under grazing pressures of 20, 40, and 50 kg/AU/day, forage disappearance exceeded intake by 28%, 48%, and 90%, respectively. These data indicate a possibility for a 2-fold increase in the efficiency of forage harvest by grazing cattle as grazing pressure is increased.
