Effects of the Replacement of Alfalfa Hay with Early-harvested First-cut Orchardgrass Silage on Digestion and Lactation in Dairy Cows

Abstract

We evaluated the effect of feeding early-harvested first-cut orchardgrass silage (OGS) instead of imported alfalfa hay (ALH) on dry matter intake (DMI), lactation performance, ruminal fermentation, digestion, and N utilization in dairy cows. Six multiparous Holstein cows were used in a replicated 3×3 Latin square design with three dietary treatments, involved gradually replacing ALH and flaked corn with 2 incremental levels of OGS (0, 50, 100%). We observed that dry matter and fiber digestibility, DMI and fat-corrected milk yield increased with an increasing OGS level in the diet. The rumen total volatile fatty acid concentration was not affected by dietary treatment. The ruminal ammonia-N concentration and the proportion of acetate and butyrate increased, and propionate decreased linearly with the increasing levels of OGS. As a proportion of N intake, the urinary N excretion decreased and the retention of N increased with increasing levels of OGS, with no dietary effect observed on N secretion in milk and fecal N excretion. These results show that OGS can be used as a substitute for ALH and flaked corn and that replacing ALH with OGS can be a good approach to improve milk production and N utilization and reduce concentrate input.