Development of Techniques for Evaluating Grazed Forage

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Abstract
Techniques were developed to sample grazed forage with steers, using both esophageal and rumen fistulas. Comparisons between feeds of known composition and samples collected from these same feeds through fistulas indicated that some changes in composition occurred. These changes in composition of certain constituents were influenced by type of feed and type of fistula. Regression equations for the various changes were calculated. The relative amounts of organic constituents were modified by fistula sampling. The amount of protein and ether extract was the same in the fistula sample as the feed, but significant changes were noted in the amount of crude fiber, NFE, and energy. Fistula samples were highly contaminated with mineral matter. The composition and amount of saliva secreted while consuming a sample of forage was investigated, to explain some of the chemical changes noted in fistula samples. Repeated feed sampling on the same day with the same animal had little effect on the composition of fistula samples. Due to the high variation between feeds, and the generally high correlations between feed and fistula samples, it was felt that the fistula sample represents the best estimate of the foraging animal''s diet until adequate comparisons of grazed forage have been made. Fistulated animals were used as sampling agents on pasture. The fistula sample could be separated botanically, between grasses and broad-leaved plants.