Rumen-protected lysine supplementation increased milk production in dairy cows fed a lysine-deficient diet

The objectives of this study were (1) to determine the effects of 3 levels of a rumen-protected Lys (RP-Lys) prototype on milk production in dairy cows fed a diet deficient in MP-Lys and (2) to assess the effects of treatments using AMTS.Cattle.Professional (AMTS = Agricultural Modeling and Training System; Groton, NY). Ten multiparous, Holstein cows were used in a 5 × 10 Latin rectangle (rows = five 18-d periods, columns = 10 cows). Treatments were (1) control (0 g of RP-Lys), (2) 30 g of Lys supplemented from RP-Lys using Aji-Pro L (APL; Ajinomoto, Chicago, IL), (3) 17.5 g of Lys supplemented from RP-Lys prototype (RPLL), (4) 21.8 g of Lys supplemented from RP-Lys prototype (RPLM), and (5) 31.5 g of Lys supplemented from RP-Lys prototype (RPLH). The basal diet was formulated with a MP-Lys balance of −16.5 g/d. Milk and blood samples were analyzed for milk components and plasma AA concentrations. Treatments were assessed for MP-Lys balance using actual chemical composition of feed ingredients, DMI, and milk production using the AMTS. Regression analysis revealed that RP-Lys prototype supplementation increased milk and lactose yields linearly (P = 0.03 and 0.04). There was a trend for RP-Lys prototype to increase protein percent quadratically (P = 0.07). Treatments did not affect plasma Lys concentrations. The retrospective evaluation of treatments showed an MP-Lys balance of −17 g/d for control and −2, −7, and 8 g/d for RPLL, RPLM, and RPLH treatments, respectively. Collectively, these results indicated that the RP-Lys prototype delivered Lys to support milk production. Results indicate that supplementation with an RP-Lys prototype increased milk production in cows fed a diet deficient in RP-Lys. These results may benefit dairy cows fed corn-based diets.