2022 Volume 68 Issue 1 Pages 8-15
We evaluated the effect of feeding early-harvested first- or second-cut orchardgrass silage on dry matter intake, lactation, 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. The diets involved gradually replacing first-cut silage with second-cut silage, flaked corn, or soybean meal at two incremental levels of 50% and 100%. All experimental diets contained 73% total digestible nutrients and 16% crude protein. The dry matter intake and milk production were not affected by the dietary treatment. However, fiber digestibility decreased with increasing second-cut silage, and milk fat content slightly decreased when the first-cut silage was replaced by the second-cut. Milk protein production was not affected by dietary treatment. Proportional to N intake, urinary N excretion increased; retention of N decreased with increasing levels of second-cut silage. No dietary effects were observed on N secretion in milk and fecal N excretion. These results showed that feeding second-cut silage instead of first-cut reduces fiber digestibility and N utilization, but this diet has a minor impact on feed intake and milk production when diets were formulated to contain 73% total digestible nutrient and 16% crude protein.