Date of this Version
Four trials were conducted to evaluate the supplemental value of feed grade biuret (in dry supplements) and urea (in liquid urea-molasses mixtures) when compared to natural protein and urea in dry supplements for beef cows grazing low quality dry winter range grass. Urea or feed grade biuret provided 50% of the nitrogen in 30% CP dry supplements and urea provided 50% of the nitrogen in 30% CP dry supplements and urea provided 94% of the nitrogen in 30% CP liquid supplements. Dry supplements were self-fed with salt added to limit intake.
Winter weight loss of cows fed dry urea-containing supplements was less than that of cows fed dry biuret-containing supplements, an average of 42 vs 57 kg in three trials.
Winter weight loss of cows fed 30% natural protein supplements was less than that of cows fed isonitrogenous urea-molasses liquid supplements when the cows subsisted entirely on dry winter range grass, an average of 70 vs 92 kg in two trials. Winter weight losses of cows fed natural protein and liquid supplements were similar when prairie hay was provided in addition to winter range grass.
Spring and summer gains were greatest for cows that lost the most weight during the wintering period and fall weights of cows were not significantly different. Birth weights and weaning weights of calves were not significantly affected by treatment.
Winter weight loss of cows in these trials indicated that neither biuret in a dry supplement nor urea in a liquid supplement provided an advantageous alternative to urea in dry supplements for cows wintered on low quality dry winter range grass.