Kinetics of Cell-Wall Digestion of Orchardgrass and Alfalfa Silages Treated with Cellulase and Formic Acid

Abstract

The objectives of this study were to determine the effects of cellulase (from Trichoderma longibrachiatum) combined with formic acid, applied before ensiling, on the subsequent concentration and composition of the cell wall and on the extent and rate of in situ cell-wall digestion of orchardgrass (Dactylis glomerata L.) and alfalfa (Medicago sativa L.). Treated and control forages of both plant species were ensiled for at least 60 d before being ruminally digested by two fistulated cows. Analyses of NDF, ADF, and acid detergent lignin were conducted sequentially on original and digested samples. Data were fitted with a first-order, nonlinear model to estimate extents and rates of digestion of potentially digestible NDF, cellulose, and hemicellulose. The concentration of indigestible residue and the discrete lag time before digestion were also determined for the cell-wall components. After ensiling, the mean NDF concentration of treated silages was 19% lower than that of control silages; the effect was greater for orchardgrass than for alfalfa. The extent of digestion of NDF, cellulose, and hemicellulose, respectively, was 33, 37, and 27% lower for treated silages than for control silages. Treatment effects on the extent of digestion varied between plant species. Cellulose from treated orchardgrass was digested 19% more slowly than cellulose from the control silage. Indigestible residue concentrations of NDF, cellulose, and hemicellulose, respectively, were 7, 8, and 7% lower in treated silages than in control silages. Thus, extensive cell-wall degradation by cellulase during ensiling resulted in less digestible cell-wall material for ruminal digestion but greater total cell-wall degradation, including that during ensiling and ruminal incubation, especially during early digestion in the rumen.

Ensiling characteristics and ruminal degradation of Italian ryegrass and lucerne silages treated with cell wall-degrading enzymes

“…Results of Italian ryegrass silage were mostly in agreement with those of Van Vuuren et al, 10 who found that enzyme treatment increased the rapidly degradable organic matter and reduced the rate of cellulose degradation in perennial ryegrass silage. Nadeau et al 13 reported smaller effects on legume (lucerne) than on grass (cocksfoot) silage, whereas the response in this study appeared greater when the legume crop was treated. Unlike the ®ndings of Hoffman et al, 9 both the amount and rate of NDF degradation were reduced in enzyme-treated lucerne silage.…”

“…Although several workers examined the effect of enzymes on the in situ degradation of silages, the results were variable and did not reach agreement. 9,10,12,13 The response to enzyme treatment may be different between grasses and legumes owing to certain differences in their composition and digestion of cell wall components. However, information is apparently scarce on the fermentation and digestion of enzyme-treated silages prepared from the two forage species.…”

Impact of ferulic acid esterase producing lactobacilli and fibrolytic enzymes on conservation characteristics, aerobic stability and fiber degradability of barley silage

“…In contrast, T3 silage had a lower aNDF concentration as compared to T2 silage, suggesting that plant cell wall carbohydrates within aNDF were hydrolysed by fibrolytic enzymes during the ensiling process. A reduction in aNDF concentration is a typical response of applying fibrolytic enzyme at ensiling on various forages as a result of hemicellulose and cellulose being partially hydrolysed during ensiling (Nadeau et al, 1996(Nadeau et al, , 2000Kung and Ranjit, 2001). This is supported by the observation that the rapidly degradable fraction of DM increased but the total fiber digestibility decreased in T3 treated silage in later in situ study.…”

“…Addition of exogenous fibrolytic enzyme (i.e., cellulases and xylanases) along with inoculants has been explored as another strategy to improve the digestibility of fiber in silage (Jaster and Moore, 1988;Nadeau et al, 1996;McAllister et al, 2001).…”

Effect of fibrolytic enzymes and incubation pH onin vitrodegradation of NDF extracts of alfalfa and orchardgrass

“…This indicates that those exogenous enzymes attached to the substrate before the native enzymes (Colombatto et al, 2003) to degrade a greater extent of NDF, and to increase the potentially digestible fraction (Nadeau et al, 1996). It is also possible that exogenous enzymes promote lignin solubility, reducing the indigestible fraction.…”