Production performance and nitrogen metabolism in dairy cows fed supplemental blends of rumen undegradable protein and rumen-protected amino acids in low- compared with high-protein diets containing corn distillers grains

Feeding corn dried distillers grains with solubles (DDGS) in low crude protein (CP) diets could limit N waste lactating cows. However, it also possibly reduce metabolizable AA supply, especially Lys, and compromise milk production. Therefore, the objective of this study was to evaluate effects feeding supplemental blends rumen undegradable (RUP) rumen-protected (RP) a compared high CP diet containing DDGS on production selected measures utilization. Six multiparous Holstein cows (619.3 ± 49.8 kg body weight; 26.8 6.2 d milk) were subjected split-plot, 3 × Latin square design (21-d periods) dietary content [low (14.6%; LP) or (16.6%; HP)] as whole-plot factor, blend RUP RP-AA [control (CON), no supplement; A (0.11 kg/cow per d); B (0.45 d)] sub-plot factor. All contained 10% DDGS; top-dressed during morning feeding. There interaction for all measured variables. Nutrient (dry matter, organic neutral detergent fiber, acid CP), component yields, feed apparent efficiency did not differ fed low- high-protein diet. total-tract digestibility, blood urea-N concentrations, urinary excretion (g/d) lower low-protein effect nutrient intake yields. Except tendency total purine derivative microbial flow be CON but A, there Both had marginal plasma free profile. In summary, reducing lactation performance, accounting lack positive response following provision RP-AA. resulted decrease urea-N, suggestive an improvement use.