Effect of Physical form of Ration upon Digestion and Volatile Fatty Acid Production in Vivo and in Vitro

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Abstract
Pelleted roughage was more readily consumed by lambs than finely ground roughage. The rate of gain produced by lambs consuming pellets or crushed pellets was greater than that made by lambs consuming an equal amount of finely ground hay. When feed intake was constant, the concentration of total volatile fatty acids in the rumen of lambs fed pellets or crushed pellets was higher than for lambs fed long or coarsely ground hay. The relative concentration of propionate and butyrate was greatest for the lambs fed the two rations which had been subjected to the pelleting process. Pelleting a finely ground hay did not decrease the digestibility of any of its constituents. The digestibility of the ether extract in the pelleted hay was greater than that of the nonpelleted hay. The in vitro cellulose digestion coefficients were greater for the dehydrated alfalfa meal than for either of the forms of sun-cured hay. The digestibility of the cellulose fractions of the pelleted hay was greater than that of the ground hay. The number or relative activity of the microorganisms present in the inoculum appeared to assert a greater effect in controlling the total amount and relative concentration of the volatile fatty acids produced in vitro than the processing to which the substrate had been subjected.