Lactational performance of dairy cows in response to supplementing N-acetyl-l-methionine as source of rumen-protected methionine

Abstract

The objective of this experiment was to evaluate the effects of supplementing a rumen-protected source of Met, N-acetyl-l-methionine (NALM), on lactational performance and nitrogen metabolism in early-to midlactation dairy cows. Sixty multiparous Holstein dairy cows in early lactation (27 ± 4.3 d in milk, SD) were assigned to 4 treatments in a randomized complete block design. Cows were blocked by actual milk yield. Treatments were as follows: (1) no NALM (control);(2) 15 g/d of NALM (NALM15); (3) 30 g/d of NALM (NALM30); and (4) 45 g/d of NALM (NALM45). Diets were formulated using a Cornell Net Carbohydrate and Protein System (CNCPS) v.6.5 model software to meet or exceed nutritional requirements of lactating dairy cows producing 42 kg/d of milk and to undersupply metabolizable Met (control) or supply incremental amounts of NALM. The digestible Met (dMet) supply for control, NALM15, NALM30, and NALM45 were 54.7, 59.8, 64.7, and 72.2 g/d, respectively. The supply of dMet was 88, 94, 104, and 115% of dMet requirement for control, NALM15, NALM30, and NALM45, respectively. Milk yield data were collected, dry matter intake (DMI) was measured daily, and milk samples were collected twice per week for 22 wk. Blood, ruminal fluid, urine, and fecal samples were collected during the covariate period and during wk 4, 8, and 16. Data were analyzed using the GLIMMIX procedure of SAS (SAS Institute) using covariates in the model for all variables except body weight. Linear, quadratic, and cubic contrasts were also tested. Treatments did not affect DMI, milk yield, and milk component concentration and yield; however, feed efficiency expressed as milk yield per DMI and 3.5% fat-corrected milk per DMI were quadratically affected, with greater response observed for NALM15 and NALM30 compared with control. Acetate proportion linearly increased, whereas propionate proportion linearly decreased with NALM supplementation. Blood urea nitrogen linearly decreased with NALM supplementation. Total plasma essential AA concentrations were quadratically affected, as greater values were observed for control and NALM45 than other treatments. Plasma Met concentration was quadratically affected as lower levels were observed with NALM15, whereas Met concentrations increased with NALM45 compared with control. Nitrogen utilization efficiency and apparent total-tract nutrient digestibility were not affected by treatment. Supplementation of NALM at 15 or 30 g/head per day resulted in the greatest improvements in feed efficiency without affecting N metabolism of early-to mid-lactation dairy cows.

Meta-Analysis of Rumen-Protected Methionine in Milk Production and Composition of Dairy Cows

“…The difference between adding different RPM contents could be ignored. The results showed that adding RPM to the diet did not significantly improve the milk yield of the dairy cows, which was consistent with the research results of some scholars [ 2 , 5 ], Although the dairy NRC (2001) pointed out that adding RPL or RPM can improve milk yield, which is likely to be achieved by improving the efficiency of the MP in milk protein synthesis, there are also reports that adding methionine + lysine can improve the milk yield more than providing only one AA [ 24 , 25 , 26 ]. As for the results for the milk composition index, adding RPM to the diets of dairy cows can significantly improve the milk fat rate and milk protein rate.…”

“…The retrieved studies were screened according to the corresponding inclusion criteria. After excluding the duplicate and unqualified literature, the meta-analysis included 14 studies, as shown in Table 1 [ 1 , 2 , 5 , 13 , 14 , 15 , 16 , 17 , 18 , 19 , 20 , 21 , 22 , 23 ]. To make it easier to visualize the studied datasets, the mean, maximum, minimum, and standard deviation of each study parameter are summarized in Table A1 of Appendix A .…”

“…It was found that adding RPM could increase the milk yield and fat percentages of dairy cows [ 3 , 4 ]. However, the results of some studies have shown that RPM does not significantly affect the milk yield or composition [ 5 ]. Due to differences in the experimental designs, feeding environments, RPM purity, and cow breed selection, we assume that RPM has a certain impact on the milk yield and milk compositions, but we do not know the extent of its impact.…”

Plasma methionine appearance and residual potential of supplemented N‐acetyl‐L‐methionine through ruminal or abomasal infusion in dairy cows

“…Liang et al (2019) reported that NALM supplemented at rates of 0, 15, 30, and 60 g/day to mid-lactation dairy cows improved milk yield in a quadratic manner, with 30 g/day of NALM seeming to be the optimal supplementation rate for milk yield under the experimental conditions. Amaro et al (2022) found that milk yield of early lactating Holstein dairy was not altered by three different supplementation rates (15, 30, and 45 g/day) of NALM compared to control animals.…”

“…Supplementation of the Met derivative increased milk fat concentration and yield (Fagundes et al, 2018), whereas supplementation of NALM to early and mid‐lactation dairy cows improved milk yield (Liang et al, 2019) and 3.5% fat‐corrected milk/dry matter intake (DMI; Amaro et al, 2022). All three studies exhibited the greatest lactational performance and feed efficiency when NALM was supplemented in lactation diets at 30 g/day (Amaro et al, 2022; Fagundes et al, 2018; Liang et al, 2019). The NALM is a Met derivative produced by chemical protection of the L‐Met α‐amino group with a N‐acetyl group.…”