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

Abstract

-In a 2 × 2 factorial approach the productive and metabolic response of 24 multiparous Brown Swiss cows fed rations calculated to be deficient in leucine (0.9-fold of requirements) and methionine (0.8-fold) to supplementation either of one or both of these amino acids were investigated. On a dry matter basis the rations consisted of 29% grass silage, 20% maize silage, 6% hay, and 45% concentrate. Blood plasma amino acid data confirmed the intended difference in metabolic supply of leucine and methionine keeping a low variation in the plasma levels of the other essential amino acids, particularly lysine. Live weight, milk yield as well as content and amount of milk fat were not affected by the treatments. Content and amount of milk protein were significantly reduced relative to initial level without additional methionine. Nutrient digestibility and nitrogen balance remained widely unchanged by the supplementations. Except of plasma aspartate amino transferase, cholesterol, creatinine and ornithine, which responded to methionine, hormones, enzyme activities as well as plasma, urine and milk metabolites were not systematically influenced by leucine and methionine supply. The present results gave clearer indications for a deficiency in methionine than in leucine.

Effect of duodenal infusions of leucine on milk yield and plasma amino acids in dairy cows

“…Our findings are in agreement with minor effects of additional Leu on milk yield and composition reported in other studies (e.g. Kröber et al, 2001;Huhtanen et al, 2002;Korhonen et al, 2002;Křížová et al, 2008). On the other hand, in a dose response study (duodenal infusions of 0, 40, 80 and 120 g/day Leu) Rulquin and Pisulewski (2006) found that milk yield was not affected by the treatments, whereas the content and yield of protein and casein varied quadratically (P < 0.05), with a maximum reached by 40 g/day Leu.…”

“…Similarly, Kröber et al (2001) confirmed that the variation in supply was clearly reflected in different plasma levels of the respective AA after feeding the experimental diets for 18 days on average. The response in terms of blood plasma concentrations of other AA to Leu supplementation is scarce and inconsistent.…”

“…Further, there was a tendency to a lower concentration of Tyr and to higher concentrations of Cys and Cit after Leu infusion (P < 0.10). This is in disagreement with Kröber et al (2001), who did not find any significant effects of Leu supply on plasma levels of Lys, Ile, threonine (Thr), valine (Val), His, and phenylalanine (Phe) as the other essential AA except arginine, and the same was ascertained for non-essential AA with the exception of asparagine and Tyr. found that the only effect of Leu infusion on plasma concentrations of other AA was a tendency of increased Phe levels and decreased Val levels.…”

“…Brandt et al (1987) suggested that under different feeding conditions such as forage-based grass/grass silage diets instead of concentratebased diets leucine might be the first or the second limiting AA in dairy cows. According to Kröber et al (2001) even mixed forage rations containing maize silage fed along with concentrate might be deficient in leucine depending on the proportion of concentrate and the type of concentrate ingredients used. Thus leucine (Leu), which is suggested to be the most-limiting from branched chain AA (e.g.…”

Effect of rumen-protected protein supplemented with three amino acids on milk yield, composition and fatty acid profile in dairy cows

“…Korhonen et al (2000) mentioned His as the first limiting AA in diets based on grass silage and, according to Vanhatalo et al (1999) His has been identified as a potentially limiting AA for milk production. Other authors mentioned as limiting the combinations of Met with Leu (Krober et al, 2001) and/or with His and Arg (Xu et al, 1998). The problem of limiting AA has been relatively well investigated in studies on the supply of Met and Lys but not enough data are available for other AA or their combinations.…”