Effects of grain processing and supplementation with exogenous amylase on nutrient digestibility in feedlot diets

• Published in: Livestock science 2011-05, Vol.137 (1-3), p.178-184
• Main Authors: DiLorenzo, N., Smith, D.R., Quinn, M.J., May, M.L., Ponce, C.H., Steinberg, W., Engstrom, M.A., Galyean, M.L.
• Format: Article
• Language: English
• Subjects: acidosis; alpha-amylase; Amylase; Angus; animal performance; corn; Digestibility; digestive system diseases; energy efficiency; experimental diets; feedlots; fermentation; flaking; Grain processing; large intestine; rumen fermentation; small intestine; starch; steam; steers
• ISSN: 1871-1413; 1878-0490
• DOI: 10.1016/j.livsci.2010.11.003

Starch is the major source of energy in the diets of feedlot cattle, comprising 50% or more of the dietary DM. With limitations to starch digestion in the small intestine and low energetic efficiency of starch fermentation in the large intestine, it is important to maximize ruminal starch digestibility, while concurrently minimizing digestive disorders such as acidosis. Grain processing is the most common strategy to increase ruminal digestion of starch. Supplemental amylase has been proposed as a means of improving total tract starch digestion, but research on the effects of exogenous amylase in feedlot diets is limited. To evaluate addition of amylase to feedlot diets, 32 Angus and Angus-crossbred steers were used in a randomized complete block design with replication of treatments in the block in a 2×2 factorial arrangement. Factors included grain processing method (dry-rolled corn [DRC] or steam-flaked corn [SFC]) with or without α-amylase (RumiStar; DSM Nutritional Products, Inc., Kaiseraugst, Switzerland) supplemented at 600kilo novo units (KNU)/kg of dietary DM. One KNU is the amount of enzyme that releases 6μmol of p-nitrophenol per min at pH 7.0 and 37°C. Steers gradually adapted a 90% concentrate finishing diet for 28d, during which the DRC and SFC treatments were applied. Amylase was supplemented when steers reached ad libitum intake of the 90% concentrate diet (d 1 of experimental period). Experimental diets were fed for 42d, and 0.25% (DM basis) of Cr2O3 was included in the diet for 11d as an indigestible marker for measurement of nutrient digestibility from d 39 to 42. Supplementation with amylase did not affect nutrient digestibility (P≥0.21) or DMI, ADG, and G:F for the 42-d period (P≥0.35). The SFC diets had 28% less total tract digestibility of NDF (P