Measurement of the Nutritive Value of Alfalfa and Timothy Hay by Varied Techniques

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Abstract
Four mature rumen-fistulated Holstein cows were divided into 2 pairs and fed alfalfa and timothy hay by the double-reversal system over a 24-wk. period divided into four 6-wk. periods, in which the last 3 wk. of each period constituted the trial proper. Digestibility of dry matter, protein, fiber, N-free extract, ether extract, energy, cellulose, lignin, and pentosans was determined by 2 procedures: (a) by the conventional procedure in which total feces were collected for ten-day periods, (b) by rumen technique, using Dacron bags containing weighed amounts of chopped forage which were placed in the rumen for periods of 48 hr. Content of the volatile fatty acids (VFA) in the rumen fluid was determined in samples taken on 38 occasions throughout the entire feeding period for each kind of hay. Measured by the conventional procedure (total feces collection), timothy was more digestible than alfalfa in all entities except protein, N-free extract, and lignin. Measured by the rumen (Dacron bag) technique, timothy was on a par with, or more digestible than, alfalfa in all entities except protein and N-free extract. Analysis of the rumen fluid showed content of VFA and ammonia to be higher when alfalfa or high-protein timothy was fed. Acetic acid constituted a slightly higher percentage of the total acidity when timothy was fed; this may have been responsible for a slightly higher butter fat test.