PSVI-18 Effects of rumen-protected lysine on performance and plasma amino acid metabolism in early lactation Holstein cows

Abstract

Abstract The objective of the current study was to evaluate the effects of rumen-protected lysine (RPL) supplementation on performance and plasma amino acids in Holstein cows. A total of 40, primi- and multiparous Holstein cows (DIM 49 ± 13) were assigned to 1 of 2 treatments in a randomized complete block design consisting of 20 blocks. Total length of the experiment was 49 d. From d1 to d7 cows were not fed RPL (adaptation phase; covariate) and from d8 to d49 (experimental phase) cows received the treatments that were top-dressed. Treatments were as follow: cows fed a basal TMR + 300 g of dried ground molasses (CON); and basal TMR + RPL (NPL; ADM, Decatur, IL) at 0.41% of the TMR DM. Blood samples were taken from the coccygeal vein or artery, on d 7, 14, 28, 42, 45, and 49 of each period from each cow. Statistical analysis was performed using the MIXED procedure in SAS (v9.4). There was no difference for DMI in cows in CON and NPL (P > 0.21). Cows in NPL had a tendency for lower BCS (3.22 ± 0.04) than CON (3.32 ± 0.03) (P = 0.06). There were no treatment differences for BW (P = 0.30) and milk protein [CON (2.94 % ± 0.04) and NPL (2.93 % ± 0.05) (P = 0.85)]. Cows in CON (64.35µM/L ± 2.06) had lower (P = 0.03) Lys plasma concentration then NPL (71.14 µM/L ± 2.11). Cows in CON (64.52 µM/L ± 1.35) had tendency for lower (P = 0.08) Arg concentration than NPL (67.98 µM/L ± 1.38). In conclusion, NPL did not improve nor decreased DMI, milk yield and components; but increased plasma Lys and Arg, concentrations in early lactation Holstein cows.