Effects of feeding different forms of lysine supplements on lactational performance and nitrogen utilization by mid- to late-lactation dairy cows

Abstract

Objective: We investigated the lactational performance and N utilization of dairy cows fed different forms of Lys supplements with the main focus on Lys derivatives ofN-acetyl-L-Lys (NALL) during mid to late lactation. Materials and Methods: Forty lactating Holstein dairy cows (151 ± 78.0 DIM) were assigned to 1 of 4 treatments (n = 10) in a randomized complete block design. The 4 dietary treatments were as follows: (1) TMR without Lys supplementation (control), (2) TMR withNε-acetyl-L-Lys supplementation at 51.5 g/d (εNALLT), (3) TMR withNα, ε-acetyl-L-Lys supplementation at 63 g/d (diNALLT), and (4) TMR with commercial rumen-protected Lys (AjiPro-L, Ajinomoto Heartland Inc.) supplementation at 100 g/d (CRPLT). Results and Discussion: Feeding of diNALLT and the CRPLT decreased DMI. Milk yield, component yield, and component concentrations were not affected by Lys supplementation. In contrast, feed conversion efficiency (milk yield/DMI) was greatest for diNALLT. The efficiencies of 3.5% FCM yield/DMI and ECM yield/DMI did not differ among treatments. Feeding the diNALLT and the CRPLT tended to reduce manure N excretion compared with the control and the εNALLT. Overall, results from the current study suggest that supplementing a Lys derivative, diNALL, to mid- to late-lactation dairy cows resulted in similar production performance relative to a commercial rumen-protected Lys product. Implications and Applications: A sizable increase in feed conversion efficiency (milk yield/DMI) and a trend for a reduction in manure N excretion when cows were supplemented with diNALL resulted from its effect to reduce DMI and N intake. This result indicates that the developmental diNALL product is metabolically active in lactating dairy cows. Further investigation is warranted to understand the biological availabilities of NALL in lactating dairy cows.