Effect of enzyme preparations on in situ and in vitro degradation and in vivo digestive characteristics of mature cool-season grass forage in beef steers.

Abstract

In situ and in vitro studies with a 3 x 2 x 5 factorial arrangement of treatments with an added untreated control evaluated three enzyme preparations, two levels of enzyme, and five moisture conditions of grass forage. Enzyme preparations predominantly contained cellulase and xylanase and will be designated as enzyme 1 (E1), enzyme 2 (E2), and a 50:50 combination of E1 and E2 (E1E2). The five moisture conditions included fresh, wilted, dried and rehydrated to fresh, dried and rehydrated to wilt, and dried grass. Addition of the high level of E1E2 to dried grass improved (P < .05) in vitro DM (43.5 vs 38.7%) and NDF (31.1 vs 26.0%) disappearance (48 h incubation) compared with the control treatment. Also, IVDMD was greater (P < .05) for the low level of E1 applied to wilted grass compared with the control. No other enzyme application improved in situ or in vitro disappearance of substrate over the control. In vivo responses of enzyme treatments found most likely to be effective from degradability studies were measured using four ruminally cannulated steers in a 4 x 4 Latin square experiment. Treatments examined were E1 applied to fresh forage, then dried; E1 applied to wilted forage, then dried; E1E2 applied to dry forage immediately before feeding (E-dry), and untreated forage (control). All forage treatments were harvested as dry hay. Total diet and hay DM intakes were greater (P < .05) for the E-dry than for the control diet. Rate of in situ NDF disappearance and total tract DM and NDF digestibility were greater (P < .05) for the E-dry than for the other treatments. Ruminal fluid ammonia N concentration, total VFA concentration, and pH were not altered (P > .10) by dietary treatment. Ruminal particulate passage rate was greater (P < .05) and ruminal retention time was shorter (P < .05) for the E-dry than for the control treatment. Data from this study suggest that addition of fibrolytic enzymes to grass hay before feeding has the potential to enhance intake and digestion.

Mode of action of exogenous cell wall degrading enzymes for ruminants

“…Numerous studies have reported increased digestion of DM and fibre measured in situ or in vitro (Nakashima et al 1988;Feng et al 1996;Hristov et al 1996;Yang et al 1999;Colombatto 2000;Colombatto et al 2002) or in vivo (Feng et al 1996;Krause et al 1998;Yang et al 1999;Beauchemin et al 2000;Kung et al 2000). These increases in feed digestion are somewhat unexpected given the exceptionally high starch and fibre digesting capacity of the rumen.…”

“…Various studies have shown that exogenous enzymes enhanced rate of in situ or in vitro digestion measured using short-term incubations (Nakashima et al 1988;Feng et al 1996;Hristov et al 1996;Yang et al 1999;Colombatto 2000;Colombatto et al 2002). However, most studies have not found exogenous enzymes to improve the extent of in situ or in vitro digestion (Nakashima et al 1988;Feng et al 1996;Hristov et al 1996;Iwaasa et al 1999;Yang et al 1999;Colombatto 2000).…”

In vitro determination of ruminal dry matter and cell wall degradation, and production of fermentation end-products of various by-products

“…Thus, some studies conducted by Luchini et al [18], Feng et al [8] and Wilman et al [39] propose in vitro methods for determining ruminal feed degradation because of a greater speed and lower expense than in vivo and in situ methods.…”

A proposed methodology to standardize the determination of enzymic activities present in enzyme additives used in ruminant diets

“…Usually, enzymes are assayed at their optimum pH or temperature (Wood and Bhat 1988), which are generally a pH range of 4.5 to 5.5 and a temperature range of 45 to 60°C. However, in most of the published reports on enzymes as feed additives for ruminants, the experimental conditions used in the assays to determine enzyme activities were not stated Feng et al 1996;Lewis et al 1996). Furthermore, where assay conditions were stated, they rarely resemble the in vivo situations.…”