Evaluation of Isoleucine, Leucine, and Valine as a Second-Limiting Amino Acid for Milk Production in Dairy Cows Fed Grass Silage Diet

Abstract

Five Finnish ruminally cannulated Ayrshire cows were used in a 5 x 5 Latin square trial with 14-d periods to determine whether branched-chain amino acids (AA) are the second- or colimiting AA for milk protein synthesis on grass silage-cereal based diet. Mammary metabolism of AA as well as AA supply from the basal diet were also studied. Grass silage (17.5% crude protein) was given ad libitum with 9 kg/d as a cereal-based concentrate (13.8% crude protein). Treatments were basal diet without AA infusion (Control), abomasal infusion of AA mixture of His, Ile, Leu, and Val at 8.5, 14.9,27.9, and 18.3 g/d, respectively, AA mixture minus Ile, AA mixture minus Leu, and AA mixture minus Val. Glucose was infused on all treatments at 250 g/d. Amino acid infusions had no effect on dry matter intake (mean 19.2 kg/d), yields of milk (mean 25.3 kg/d), energy-corrected milk (mean 25.9 kg/d), milk protein (mean 807 g/d), lactose (mean 1261 g/d), or fat (mean 1056 g/d). Milk composition was not affected by the treatments. Plasma concentrations of His and Val responded to AA infusions but concentration of Ile increased only on treatment AA mixture minus Leu, and concentration of Leu only on treatment AA mixture minus Ile. Infusion of AA mixture of His, Ile, Leu, and Val decreased plasma concentrations of Arg, Lys, Met, Phe, and Tyr. Amino acid infusions did not affect concentrations of plasma urea and energy metabolites or AA utilization by the mammary gland. Based on unchanged production parameters, the supply of His or branched-chain AA seemed not to be limiting under the current dietary conditions. Changes in plasma AA concentrations suggest either antagonism between individual AA in absorption or increased partitioning of AA into the muscle tissues. About 75% of omasal canal nonammonia nitrogen flow (427 g/d) was of microbial origin, and AA profiles of microbial protein and omasal canal digesta were fairly similar. Postruminal AA supply seems to be dependent on the basal diet, but variation may exist even within the similar basal diets.

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

“…Similar responses to Leu supplement have been presented in other studies (e. g. , Korhonen et al 2002, Kröber et al 2001. In our study, we found that the effects of additional Leu on milk yield and composition were minor.…”

“…Rulquin et al (2001a) proposed Leu as a limiting AA for diets with low contents of maize. Although in recent studies of Korhonen et al (2002) and Huhtanen et al (2002), nonsignificant or inconsistent production responses to supplemental Leu were obtained in experiments with cows fed on grass/grass silage based diets, the Leu limitation in maize silage-concentrate diets is unclear (Kröber et al 2001, Rulquin et al 2001a. The objective of the present study was to establish, based on changes in milk yield and composition and plasma AA, the role of Leu given in the form of rumen protected tablets as a possible third-limiting AA in milk production of cows fed a maize silageconcentrate based diet.…”

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.…”

“…Similar responses to Leu supplement have been reported in other studies in which Leu was supplemented either in the ruminally protected form (Křížová et al, 2008) or in the form of abomasal Korhonen et al, 2002) or duodenal infusions (Rulquin and Pisulewski, 2006).…”

The Relationship between Changes in Serum Glycine and Alanine Concentrations in Non-Essential Amino Acid and Milk Production in the Transition Period in Dairy Cows

“…During this time the dairy cow undergoes significant physiologic changes including regeneration of the mammary gland tissue, rapid fetal growth, a reduction of dry matter intake (DMI) immediately pre-partum followed by a rapid increase post-partum, and significant repartitioning of nutrients toward lactation [1]. Serum free amino acid (FAA) concentration is influenced by muscle catabolism [1,4], amino acid profile [6] and gastrointestinal absorption [5]. The concentration of most FAAs decreases abruptly in pre-partum cows, however, glycine (Gly) increases [5,7,8].…”