Abstract
The aim of this study was to determine the influence of leucine supplement in the form of rumen-protected tablets on milk yield and composition and plasma amino acids in four high-yielding lactating Holstein cows. The experiment was carried out as a cross-over procedure and was divided into 4 periods of 14 d (10 d preliminary period and 4 d experimental period). Cows were fed ad libitum a diet based on maize silage, lucerne hay and a supplemental mixture. The diet, defficient in methionine, lysine, and leucine, was supplemented with methionine+lysine (Control) or methionine+lysine+leucine (Leu) in rumen protected form. The dry matter intake, milk yield and milk yield expressed in energy corrected milk did not differ significantly between the treatments. Milk protein content and yield did not show statistically significant variation. The contents and yield of casein, fat, lactose and urea were unaffected by the treatment. Blood metabolites did not vary between the treatments. The introduction of Leu resulted in higher plasma levels of proline (p
Highlights
Results of several experiments comprising postruminal infusion of amino acids (AA) suggest that AA supply in the feed of lactating cows is qualitatively or quantitatively suboptimal
The aim of this study was to determine the influence of leucine supplement in the form of rumen-protected tablets on milk yield and composition and plasma amino acids in four high-yielding lactating Holstein cows
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
Summary
Results of several experiments comprising postruminal infusion of amino acids (AA) suggest that AA supply in the feed of lactating cows is qualitatively or quantitatively suboptimal. Providing an adequate pattern of AA for absorption in the small intestine may facilitate achieving optimum productivity in high-yield dairy cows by increasing the content and yield of milk protein (Rulquin and Vérité 1993). The knowledge of limitations in individual essential. AA allows supplementing these AA with minimum additional nitrogen (N). Composition (Blouin et al 2002) of diet can vary the pattern and amount of absorbed AA. Schwab et al (1993) emphasized that optimizing intestinal AA balance is more important in improving milk protein production than crude protein (CP) content of the ration.
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