Blood methionine and lysine concentration in lactating dairy cows supplemented with commercial rumen-proteced methionine and lysine products

A. Gallo, G. Fusconi, L. Fiorentini, E. Grilli, P. Fantinati and F. Masoero.

(2010) Third International Symposium on Energy and Protein Metabolism and Nutrition (ISEP), September 6-10

It is well known that methionine (Met) and lysine (Lys) are two of the most limiting amino acids (AA) for milk and protein production in lactating dairy cows fed corn-based diets (Schwab et al., 2003; Rulquin, 2004). The NRC (2001) suggested concentrations of Met and Lys of 2.4% and 7.2% on a metabolizable protein (MP) basis, respectively, in order to maximize the use of MP for milk and milk protein yield by lactating dairy cows. However, it should be taken in consideration that these concentrations are hardly achieved. Nutritionists have two methods to feed lactating dairy cows with AA balanced diets: one is to incorporate feeds with a high level of rumen undegradable protein, and the other is to supplement the diet with ruminally protected (RP) synthetic AA (Schwab et al., 2003). The aim of this work was to assess the bioavailability of a RP D,L-Met and RP L-Lys HCl products by a standardized blood test (Südekum et al., 2004).