Effect of AmafermŽ on Digestion of Diets Containing Forages with High or Low Neutral Detergent Fiber Digestibility

Abstract Text: Amaferm^® (AF), an extract obtained from fermenting Aspergillus oryzae, has been reported to stimulate fiber degrading ruminal fungi and bacteria. The objective of this study was to measure effects of AF on fermentation of typical lactation dairy cow rations containing forages with high NDF digestibility (NDFd) or low NDFd.  Corn silage (CS) and alfalfa haylage (AH) with 30 h NDFd of 66.4 and 41.4 % of NDF, respectively, were used as the only forages to formulate a high NDFd ration (HFd).  A CS and AH with 30 hr NDFd of 51.2 and 34.3 % of NDF, respectively, were used as the only forages to formulate a low NDFd ration (LFd).  Diets were formulated to contain (DM basis) 16.0 % NDF from CS and 8.0 % NDF from AH.   Corn, soybean meal, urea, blood meal, Megalac^® and molasses were adjusted to equalize CP, soluble CP, starch, nonfiber carbohydrates and fat between diets. A completely randomized experimental design was used with a 2 x 2 factorial arrangement of diet forage NDFd (high or low) and level of AF (0.0 or 0.06 % of DM).  Diets were fermented in triplicate in continuous culture fermentors at the Rumen Fermentation Profiling Laboratory, West Virginia University, Morgantown, West Virginia.  Data on pH were reduced to daily means for each fermentor.  Fermentation data were analyzed using the MIXED procedure of SAS with a repeated-measures model.  Fermentor was treated as a random variable.  First-order autoregressive structure type was selected as the appropriate covariance structure based on the goodness-of-fit criteria.  Digestibility (%) of DM, NDF, and nonstructural carbohydrates (NSC) were, respectively, 67.8, 41.4, and 79.3 for HFd, 66.2, 34.8, and 77.5 for HFd + AF, 62.9, 34.9, and 79.3 for LFd and 65.8, 39.6, and 79.5 for LFd + AF.  DM digestibility tended to be more for high NDFd vs low NDFd treatments (P = 0.08).  Digestibility of NSC was similar among treatments.  Adding AF improved NDF digestion of LFd but reduced NDF digestion of HFd (forage NDFd x AF interaction; P < 0.01).  Average fermentor pH for HFd, HFd + AF, LFd and LFd + AF were 6.03, 6.08, 6.31 and 6.24, respectively, with a main effect due to forage NDFd observed (P< 0.01).  Adding AF improved NDF digestion of the LFd diet but not the HFd diet.  The difference in response of HFd and LFd diets to AF may be related to differences in fermentor pH.

Keywords: Amaferm, NDF digestion,