Effect of rumen-protected methionine, lysine or both on milk production and plasma amino acids of high-yielding dairy cows
2009
Trinacty, J.,Vyzkumny Ustav pro Chov Skotu, Rapotin (Czech Republic) | Krizova, L.,Agrovyzkum, Rapotin (Czech Republic) | Richter, M.,Agrovyzkum, Rapotin (Czech Republic) | Cerny, V.,Milcom, Tabor (Czech Republic) | Riha, J.,Agrovyzkum, Rapotin (Czech Republic)
The objective of this study was to determine the effect of supplemental lysine (Lys), methionine (Met) or both amino acids added in the form of rumen-protected (RP) tablets with copolymer coating to a diet of dairy cows on yield and composition of milk and concentration of plasma amino acids (AA). The experiment was carried out on four high-yielding lactating Holstein cows with average milk production of 33.5 kg/day in the form of Latin square design. The four treatments were as follows: C - control without AA supplementation, L - control plus supplement of RP Lys, M - control plus supplement of RP Met and ML - control plus supplement of RP Met and Lys. The experiment was divided into 4 periods. Each period (14 days) consisted of 10-day preliminary period and 4-day experimental period. Cows were fed a diet based on maize silage, lucerne hay and supplemental mixture. Average milk yield recorded in ML was 34.18 kg and was higher than that recorded in L or M (32.46 kg and 32.13 kg, respectively, P less than 0.05) and tended to be higher than in C (33.33 kg, P less than 0.05). The content of protein and casein was higher in L and ML in comparison with C (P less than 0.05) and tended to be higher than in M. Protein yield in ML (1 054 g/day) was higher than that found in C, L or M (990, 998 or 968 g/day, respectively, P less than 0.05). The same response was found for casein yield (P less than 0.05). Although the proportion of individual casein fractions was not affected by the treatment, the yield of alpha and beta-casein differed (P less than 0.05) while the yield of kappa-casein was not affected by the treatment. Concentrations of blood metabolites, except for betahydroxybutyrate, were not changed. Plasma Met concentrations were increased (P less than 0.05) in the M and ML group. Similar, but insignificant increases were also observed in plasma Lys in the L and ML group.
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