CHOICE OF THE MOST SUITABLE ENZYME FOR DE TERMINATION OF RUMEN DEGRADABILITY OF DIETARY-PROTEIN

The objective of the present paper was to choose a suitable enzymic pr eparation for determination of protein degradability Three proteases w ere used in the trial: papain (Loba, Switzerland), pronase (Serva, Ger many) and bromelain (Sigma, USA). Enzyme concentrations in the termina l enzymic solution: papain - 12 mg/ml phosphate buffer, pH 6; bromelai n - 6 mg.ml phosphate buffer, pH 7.2; pronase - 2 mg/ml phosphate-bora te buffer, pH 8. A set of feeds consisted of both bulk feeds and grain s (n = 13 x 3): green alfalfa, green clover, meadow grass, alfalfa hay , alfalfa haylage, com silage, ensiled beet tops, pea + wheat, fish me al, ground-nut meal, wheat, pea and wheat bran. Enzymic reactions were performed at a temperature of 40-degrees-C. Chloramphenicol addition was to reduce the effect of microbial contamination. Feed incubation i n buffer lasted 24 hours. After incubated feed mineralization, ammonia content in mineralizate was determined by Nessler method after Kjelda hl. The results obtained by the methods in sacco and in vitro were com pared. Regression equations and correlation coefficients were calculat ed. Tab. I shows the values of protein degradability determined by the methods in sacco and in vitro using the particular enzymes after 24 h ours of incubation. Tab. II indicates a relationship between the value s determined in sacco and the values determined enzymatically by calcu lations of linear regression equations for the particular enzymes with in the entire set of samples. The comparison of enzymes shows that the enzyme bromelain had the highest value of correlation coefficient whi le the values for papain and pronase were lower. Suitability of using bromelain protease for prediction of protein degradation was demonstra ted by assessment of the relationship between the values in sacco and the values in vitro in the given set of feeds.