Effect of exogenous fibrolytic enzymes and ammonia fiber expansion on the fermentation of wheat straw in an artificial rumen system (RUSITEC)1. (1st July 2019)

• Record Type: Journal Article
• Authors: Saleem, Atef M; Ribeiro, Gabriel O; Sanderson, Haley; Alipour, Daryoush; Brand, Tassilo; Hünerberg, Martin; Yang, Wenzhu Z; Santos, Laize V; McAllister, Tim A
• Is Part Of: Journal of animal science. Volume 97:Number 8(2019)
• Page Start: 3535
• Page End: 3549
• Publication Date: 2019-07-01
• Subjects: AFEX -- fibrolytic enzymes -- fiber -- rumen fermentation -- RUSITEC; Livestock -- Periodicals; Livestock; Electronic journals; Periodicals; 636.005
• DOI: 10.1093/jas/skz224
• Languages: English
• ISSNs: 0021-8812

Abstract

Abstract: This study investigated the effect of treatment of wheat straw using ammonia fiber expansion (AFEX ) and exogenous fibrolytic enzymes (Viscozyme) on fiber digestibility, rumen fermentation, microbial protein synthesis, and microbial populations in an artificial rumen system [Rumen Simulation Technique (RUSITEC )]. Four treatments were assigned to 16 vessels (4 per treatment) in 2 RUSITEC apparatuses in a randomized block design. Treatments were arranged as a 2 × 2 factorial using untreated or AFEX-treated wheat straw with or without exogenous fibrolytic enzymes [0 or 500 μg of protein/g straw dry matter (DM)]. Fibrolytic enzymes were applied to straw, prior to sealing in nylon bags. The concentrate mixture was provided in a separate bag within each fermentation vessel. The RUSITECs were adapted for 8 d and disappearance of DM, neutral detergent fiber (NDF), acid detergent fiber (ADF), and crude protein (CP) was measured after 48 h of incubation. Ammonia fiber expansion increased ( P < 0.01) the disappearance of wheat straw DM (69.6 vs. 38.3%), NDF (65.6 vs. 36.8%), ADF (61.4 vs. 36.0%), and CP (68.3 vs. 24.0%). Total dietary DM, organic matter (OM), and NDF disappearance was also increased ( P ≤ 0.05) by enzymes. Total microbial protein production was greater ( P < 0.01) for AFEX-treated (72.9 mg/d) than untreated straw (63.1 mg/d). Total gas and methane (CH4 ) production ( P < 0.01) were also greater for AFEX-treated wheat straw than untreated straw, with a tendency for total gas to increase ( P = 0.06) with enzymes. Ammonia fiber expansion increased ( P < 0.01) total volatile fatty acid (VFA) production and the molar proportion of propionate, while it decreased ( P < 0.01) acetate and the acetate-to-propionate ratio. The AFEX-treated straw had lower relative quantities of fungi, methanogens, and Fibrobacter succinogenes ( P < 0.01) and fewer protozoa ( P < 0.01) compared to untreated straw. The pH of fermenters fed AFEX-treated straw was lower ( P < 0.01) than those fed untreated straw. Both AFEX ( P < 0.01) and enzymes ( P = 0.02) decreased xylanase activity. There was an enzyme × straw interaction ( P = 0.02) for endoglucanase activity. Enzymes increased endoglucanase activity of AFEX-treated wheat straw, but had no effect on untreated straw. The addition of enzymes lowered the relative abundance of Ruminococcus flavefaciens, but increased F. succinogenes . These results indicate that AFEX increased the ruminal disappearance of wheat straw and improved fermentation and microbial protein synthesis in the RUSITEC.