Evaluation of a source of α-amylase and a protease in the diet of lambs on nutrient intake and digestibility and blood parameters

Abstract Text: The effects of a commercial source of α-amylase and an experimental protease or their combination on nutrient intake and digestibility and blood parameters were determined in lambs fed 21% dietary starch. Twelve crossbred lambs (14.2 kg) were assigned to one of four diets; no additive (control) or diets containing α-amylase (RONOZYME RumiStar®), an experimental protease, or their combination. Diets were offered daily at 4% of animal BW/DMB in four 28-day experimental periods consisting of 21 d of adaptation to the diet followed by 7 d of complete fecal collection.  In each period, feed offered, orts, and feces were collected, quantified, and analyzed for DM, starch, CP, and NDF contents to determine intake and digestibility.  Disease incidence was observed and recorded during the experiment. Blood samples were collected from each lamb at the end of each experimental period to determine glucose, BHB, NEFA, and insulin concentrations. Data were analyzed according to a 4 x 4 Latin Square experimental design.  Treatments contrasts were performed using least squares means adjustment for multiple comparisons (Tukey-Kramer) between diets as follows: containing enzymes versus no enzymes, amylases versus no amylases, proteases versus no proteases, and amylases versus proteases.  Adding proteases to the diet decreased (P<0.05) starch consumption as compared to that of lambs fed without the experimental enzyme (248.5 vs. 255 g/d).  Starch digestibility also tended (P<0.10) to be higher in lambs fed with the protease than with α-amylase (98.9% vs. 98.5%). Adding enzymes to the diet tended (P<0.10) to decrease BHB concentration (4.26 vs. 4.68 mg/dL). NEFA concentration tended to decrease (P<0.10) for lambs fed α-amylase as compared to lambs fed diets without α-amylase (0.128 vs. 0.156 mEq/L).  Insulin levels were lowered (P<0.05) by addition of α-amylase in lambs diets as compared to those of animals fed with protease (73.3 vs. 80.3 pmol/L). Insulin level also tended (P<.10) to increase in lambs fed the experimental protease as compared to lambs fed the enzyme (80.3 vs. 78.7 pmol/L).  In summary, adding the experimental proteases to lambs diets containing 21% dietary starch decrease starch consumption and tended to increase starch digestibility. Both exogenous enzymes influenced blood metabolites, however a greater effect was observed in lambs fed with the experimental protease.

Keywords: Enzymes, α-amylase, Protease