Ruminant Utilization of Silage in Relation to Hay, Pellets, and Hay Plus Grain. I. Composition, Digestion, Nitrogen Balance, Intake, and Growth

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 silage of Experiment 1 contained more acid detergent fiber than the hay.In Experiment 2, the silage was more highly lignified than the hay and contained more total nitrogen relative to calories.The silage nitrogen was more soluble.Compared to the hay, the silage of Experiment 1 resulted in a lower digestion of dry matter, organic matter, neutral detergent fiber, and nitrogen.In Experiment 2, the ad libitmn feeding of silage resulted in less nitrogen retained when expressed as grams per day, per cent of that fed, or per cent of that digested than the feeding of hay.In a companion o'rowth trial conducted on the forages of Experiment 2, the silage-fed animals had a lower energy intake, lower gain, and required more energy above maintenance per unit g'ain.The amount of nitrogen retained per unit weight gain indicated that the lower utilization of nitrogen on the silage ration was first caused by the lower energy relative to nitrogen.