Interactions of Ruminally Protected Methionine and Lysine with Protein Source or Energy Level in the Diets of Cows

Abstract

Interactions between supplementation with ruminally protected Met and Lys and the nature of protein or energy concentration of the diet were studied using 16 and 12 multiparous lactating dairy cows in two trials of 8 and 12 wk, respectively, commencing on approximately d 40 of lactation. In trial 1, cows received a semicomplete diet plus concentrates. The diet consisted of 62 to 63% corn silage, 2.2% corn gluten meal, .4% urea, 11% soybean meal (untreated or treated with formaldehyde), and 23 to 24% barley. In trial 2, cows received a complete diet with corn silage, untreated and formaldehyde-treated soybean meal, and barley in the ratio 78:12:9:0 or 49:13:4:33. All treatments were replicated in a 4 x 4 Latin square design. In both trials, Met plus Lys (10 g/d of intestinally available Met and 30 g/d of Lys) has no significant effect on DMI, milk yield, fat content, casein as a percentage of true protein, or urea content of the milk. Mean increase of milk protein yield was 46 g/d with Met plus Lys, and mean increase of true protein content was 1.1 g/kg of milk. The increase in content of milk true protein was greater for cows receiving the low energy diet. Protein source had no effect on milk yield or composition. Glucose, urea, NEFA, BHBA, and total free AA in plasma were unaffected by supplementation of ruminally protected Met plus Lys. However, concentrations of Met and Lys in blood were slightly, but not significantly, higher in supplemented cows.

Effects of supplying leucine and methionine to early-lactating cows fed silage-concentrate based diets with a calculated deficiency in leucine and methionine

“…Leucine and methionine level, the interaction of both and cow group (experimental period) were considered in Model 1, separately so also for the pre-experimental data if reflect their metabolic availability even when no immediate effects on milk protein synthesis occur. This could be different when the amino acids are supplied in clear excess of requirements for milk protein synthesis or in a not optimally balanced manner [6]. On this basis both leucine and methionine supply could have been deficient in the unsupplemented basal diet.…”

“…In the present study groups receiving different methionine levels did not significantly differ in content and yield of milk fat, but milk fat content significantly increased relative to initial in the Leu-/Met+ group. In some other studies additional methionine increased milk fat content [15,28] whereas some authors did not find a response to methionine [6,14]. Effects would be caused by the role of methionine in milk fat formation due to its ability to activate high-energy methyl groups for choline synthesis [9].…”

Effect of Ruminally-protected leucine supplement on milk yield and plasma amino acids in dairy cows

“…Furthermore, in the state of subclinical deficiency, changes in the plasma concentrations of supplemented AA closely reflect their metabolic availability, even when no immediate effects on milk protein synthesis occur. This could be different when the AA are supplied in clear excess of requirements for milk protein synthesis or in an unbalanced manner (Colin-Schoellen et al 1995).…”

Effects of fat-protein supplementation of diets for cows in early lactation on milk yield and composition

“…Energy deficiency in the ration as well as excessive supply of rumen degradable protein can reduce milk yield and negatively effect milk composition (Colin-Schoellen et al, 1995;Kowalski, 1997). Therefore the sources of digestible energy such as calcium salts of fatty acids (CaFA), containing rumen undegradable protein, may be a viable alternative to starch since they meet nutrient requirements of high-production cows at the peak of lactation (Kellaway and Porter, 1993;Wu and Huber, 1994;Brzóska et al, 1999a;Bolland et al, 2001;Bargo et al, 2003;Schroeder et al, 2002Schroeder et al, , 2004.…”