Ruminant Utilization of Silage in Relation to Hay, Pellets, and Hay Plus Grain. II. Rumen Content, Dry Matter Passage, and Water Intake

Abstract

Two 4 × 4 Latin-square experiments were conducted using fistulated Holstein heifers. Experiment 1 compared silage, hay, pelleted hay, and hay plus grain. Experiment 2 compared direct-cut silage and hay harvested from the same source. The wet rumen contents and dry matter percentages were determined by completely emptying the reticulorumen of each animal on each ration at four times between 12-hr feeding intervals. From these data dry rumen contents were calculated. The dry rumen content was divided by the daily dry matter consumption to obtain an average retention time. The wet and dry rumen contents of heifers when fed silage ad libitum were less than when fed hay, suggesting that silage intake was not restricted by rumen capacity. The retention time of silage was comparable to that of hay. The calculated daily fecal DM excretion relative to body weight was less for silage-fed animals than for hay-fed animals in a simultaneous growth trial, suggesting that silage intake was not limited by feed residues in the lower tract. The undigested residue in the rumen calculated from the passage of stained particles using first-order equations showed no consistent relation to the actual amount present. The difference was caused by the variable portion undergoing digestion. The animals drank less water when eating silage as compared to hay, but the total water intake per kilogram feed DM was greater on silage than on hay rations. © 1965, American Dairy Science Association. All rights reserved.