Effects of exogenous cellulase supplementation on microbial growth and ruminal fermentation of a high-forage diet in Rusitec fermenters

• Published in: Journal of animal science Vol. 85; no. 8; pp. 1962 - 1970
• Main Authors: Giraldo, L.A, Tejido, M.L, Ranilla, M.J, Carro, M.D
• Format: Journal Article
• Language: English
• Published: Savoy, IL Am Soc Animal Sci 01.08.2007; American Society of Animal Science
• Subjects: Animal Feed; Animal productions; Animals; Aspergillus niger; Aspergillus niger - enzymology; Bacteria - drug effects; Bacteria - growth & development; Bacteria - metabolism; Biological and medical sciences; Cellulase - administration & dosage; Cellulase - analysis; Cellulase - metabolism; Cellulase - pharmacology; cellulases; degradation; diet; Diet - veterinary; dietary fiber; Dietary Fiber - analysis; Dietary Fiber - metabolism; Dietary Supplements; enzymatic treatment; Fatty Acids, Volatile - analysis; Fatty Acids, Volatile - biosynthesis; Feed and pet food industries; feed concentrates; Fermentation - drug effects; fermenters; Food industries; forage; Fundamental and applied biological sciences. Psychology; gas production (biological); Hydrogen-Ion Concentration; Hypocrea jecorina; in vitro digestibility; in vitro digestion; microbial growth; Nitrogen - analysis; Nitrogen - metabolism; protein synthesis; Random Allocation; Rumen - metabolism; Rumen - microbiology; rumen fermentation; rumen microorganisms; ruminants; Rusitec fermenters; Sheep; Terrestrial animal productions; Time Factors; Trichoderma - enzymology; Trichoderma longibrachiatum; Vertebrates; volatile fatty acids; Exogenous; Microorganism growth; Enzyme; Fermenter; Fodder; microbial protein synthesis; Fermentation; Feeding; ruminal fermentation; Diet; Cellulase; Protein synthesis; Rusitec; Glycosidases; Hydrolases; Supplementation; O-Glycosidases
• ISSN: 0021-8812; 1525-3163
• DOI: 10.2527/jas.2006-318

Two incubation runs were carried out with a Rusitec system to investigate the effects of 2 exogenous pure cellulases on ruminal microbial growth and fermentation of a 70:30 grass hay:concentrate (DM basis) substrate. The substrate was sprayed with buffer (control; pH = 6.5), a cellulase from Trichoderma longibrachiatum (TRI), a cellulase from Aspergillus niger (ASP), or a 1:1 mixture of both cellulases (MIX) 24 h before being placed in the fermenters. Enzymes were applied at a rate of 30 endoglucanase units/g of substrate DM. Treating the substrate with enzymes reduced substrate NDF and ADF content (P < 0.001 to P = 0.002) and increased DM, NDF, and ADF disappearance after 6 and 24 h of incubation (P < 0.001 to P = 0.004) but not after 48 h of incubation. Daily VFA production was increased (P = 0.004) by 15, 9, and 15% for TRI, ASP, and MIX, respectively, with half of the increase being due to production of acetate. All enzyme treatments augmented (P = 0.009) methane production, but none of them altered the methane:VFA ratio (P = 0.70). There were no differences (P = 0.80) among treatments in the daily flow of solid-associated microorganisms, as measured using 15N as a microbial marker. Although the TRI and MIX treatments increased (P < 0.05) the daily flow of liquid-associated microorganisms and the proportion of microbial N in the solid residue after 48 h of incubation, no effects were observed (P = 0.92 and P = 0.95, respectively) for the ASP treatment. The results show that the TRI and MIX treatments enhanced in vitro fermentation by increasing substrate fiber degradation, VFA production, and ruminal microbial growth. The lack of differences between TRI and MIX in most of the measured variables indicates that treating the substrate with a mixture of both cellulases did not further improve the effects of the TRI treatment.