Short communication: The effect of an exogenous enzyme with amylolytic activity on gas production and in vitro rumen starch degradability of small and large particles of corn or barley meals

The objective of this study was to evaluate the effect\r\nof exogenous amylase supplementation on gas production\r\nand on in vitro rumen starch degradability (IVSD)\r\nof different sized particles of corn and barley meals\r\n(Cm and Bm, respectively). An aqueous liquid amylase\r\nformulation from Bacillus licheniformis was tested\r\nat 3 enzyme doses (EnzD; 0, 300 and 1,500 kilo novo\r\nunits/kg of dry matter) on small (<750 μm) and large\r\n(≥750 μm) particle size (PS) of Cm and Bm. Data were\r\nanalyzed according to a randomized complete block\r\ndesign with a factorial arrangement of treatments; the\r\nmain tested effects were PS, EnzD, and their interaction.\r\nFermentation run entered in the model as random\r\neffect. The mixed rumen fluid was collected from 2\r\nrumen-fistulated Holstein dry dairy cows fed at maintenance\r\n(forage:concentrate ratio of 80:20; 12% crude\r\nprotein; 55% amylase-treated neutral detergent fiber).\r\nSmall particles of both Cm and Bm had a greater rate\r\nof fermentation and shorter lag time than large particles.\r\nThe rate of starch degradation was greater for\r\nsmall than for large particles of Bm, being 0.187 and\r\n0.125 1/h, respectively. Conversely, the rate of starch\r\ndegradation of Cm averaged 0.063 1/h and was similar\r\namong treatments. Enzyme supplementation tended to\r\nreduce lag time and to increase rate of fermentation for\r\nboth PS of Cm and Bm, with a more pronounced effect\r\nfor small PS. A limited EnzD effect was measured for\r\nIVSD data and rate of starch degradation; PS influenced\r\nfermentation parameters and the magnitude of\r\nstarch degradation more than EnzD. Supplementation\r\nwith exogenous amylase influenced the rumen fermentation\r\npattern of small and large PS of Cm and Bm,\r\neven if the effect of the enzyme supplementation differed\r\naccording to the PS of cereal meals.