Effects of rumen-protected methionine and other essential amino acid supplementation on milk and milk component yields in lactating Holstein cows

Abstract

Objectives of this study were to investigate the effects of supplementing rumen-protected methionine (RP-Met), threonine (RP-Thr), isoleucine (RP-Ile), and leucine (RP-Leu) individually or jointly to a lowprotein diet, on the performance of lactating dairy cows, as well as to determine the effects of these amino acids (AA) on the mammalian target of rapamycin (mTOR) in vivo. Ten lactating Holstein cows were randomly allocated to a repeated 5 × 5 Latin square experiment with five 19-d periods. Treatments were high-protein diet (16% crude protein, positive control; HP), lowprotein diet (12% crude protein, negative control; LP), LP plus RP-Met (LPM), LP plus RP-Met and RP-Thr (LPMT), and LP plus RP-Met, RP-Thr, RP-Ile, and RP-Leu (LPMTIL). The dry matter intakes (DMI) of the LP, LPM, and LPMT diets were lower than that of the HP diet, whereas the DMI of the LPMTIL diet was intermediate between the HP diet and the other LP diets. Supplementing RP-Met to the LP diet increased the yields of milk and milk protein, increased the content of milk urea N, and tended to increase milk N efficiency. Co-supplementation of RP-Thr with RP-Met resulted in no further milk production increase. Co-supplementation of all 4 rumen-protected amino acids (RP-AA) increased milk and lactose yields to the level of the HP diet and tended to increase milk protein yield compared with the LPMT diet. We found no significant differences in the contents and yields of milk components between the LPMTIL and HP diets except for a lower milk urea N content in the LPMTIL diet. Venous concentrations of the measured AA were similar across the LP and LP diets supplemented with RP-AA. Relative to levels of the HP diet, LP diets had higher venous concentrations of Met and Gly and tended to have higher Phe concentration and lower con-centrations of Val and BCAA. The LPMTIL diet had higher venous concentrations of Arg, Lys, Met, Phe, and Glu, and a lower Val concentration. Phosphorylation status of the measured mTOR components in LPM and LPMT treatments were similar to those in the LP treatment but phosphorylation status of mTOR and eIF4E-binding protein 1 (4eBP1) in LPMTIL treatment were higher. The phosphorylation rates of eukaryotic elongation factor 2 (eEF2) in the 4 LP and LP plus RP-AA diets were higher than that of the HP diet. Overall, results of the present study supported the concept that under the relatively short time of this experiment, supplementing RP-AA, which are believed to stimulate the mTOR signal pathway, can lead to increased milk protein yield. This increase appears to be due to increased DMI, greater mTOR signaling, and greater eEF2 activity.

Replacing Soybean Meal with Distillers Dried Grains with Solubles plus Rumen-Protected Lysine and Methionine: Effects on Growth Performance, Nutrients Digestion, Rumen Fermentation, and Serum Parameters in Hu Sheep

“…Similarly, the lactation response to SBM and RP-Met of corn silage-based diets showed that when RP-Met was added to increase the Lys to Met ratio to 3 to 1, 15% CP was adequate for lactating dairy cows fed corn silage diets supplemented with SBM and lactating approximately 40 kg of milk/day, as well as improved apparent digestibility [ 19 ]. However, inconsistent findings were shown in studies of Zhao et al [ 20 ] and Lee et al [ 21 ], who reported that rumen-protected methionine and other essential AAs did not affect the apparent digestibility of dietary nutrients in the dairy cow. The reason was that the different studies used different types of RPAA, while the different RPAAs have different rumen bypass rates, rumen microbial metabolism, and apparent digestibility.…”

Inclusion of Different Level Leucaena in Dairy Ration to Balance Rumen Degradable and Undegradable Protein Ratio

“…Feed protein is one factor that determines milk protein quality [2]. Ruminants use it to maintain life, grow muscle and bone, produce milk, and maintain pregnancy.…”

Changes in Metabolites from Bovine Milk with β-Casein Variants Revealed by Metabolomics

“…In general, methionine and lysine have been considered as the central limiting factors for milk protein synthesis in the mammary gland of dairy cows. Although the reported effects of methionine supplementation on the concentration of milk proteins in lactating dairy cows are inconsistent, many previous studies have suggested that methionine addition to the diet tends to increase the protein yield and methionine content in the blood [26][27][28]. Cows with the β-casein variant A2 also tend to have a higher milk yield than those with variant A1 and show increased breeding values for milk and protein yield [29,30].…”