A Study of Factors Affecting Rate of Intake of Heifers Fed Silage

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Abstract
Dairy heifers were used to study factors that influence the rate of consumption of alfalfa silage. Consumption was linearly and positively related to dry matter content of the silage. However, this was shown to be a secondary relationship, since changing the dry matter content of silage or hay at time of feeding did not alter rate of consumption. The dry matter content of forage when ensiled, and the resulting fermentation process, are very important factors in determining rate of consumption of the resulting silage. In trials of a preliminary nature, adding limestone or other minerals, ammonium salts, molasses, commercial flavor preparations, concentrates, potassium orotate plus methionine, and an aureomycin-containing feed additive to silage had no effect on rate of silage consumption, whereas glucosamine, large amounts of lactic plus other silage acids, thyro-protein, and thiouracil had a depressing effect. The depressing effect of silage on intake is probably a metabolic effect on appetite and not a direct effect through palatability. Intake of silage and hay was reduced when the effluent liquid from a silo, aqueous extract of silage, residue after ether extraction of the effluent liquid, large quantities of lactic acid or lactic plus other silage acids, a mineral mixture, glucosamine, urea, or other ammonium salts were placed directly into the rumen. Similarly, hydrolyzed easein, tyramine, sucrose, water, acidic or basic ether soluble fractions of the silo effluent, or low levels of the silage acids had no such effect on intake. The desirability of further investigations is indicated.