Exogenous fibrolytic enzymes to unlock nutrients: Histological investigation of its effects on fibre degradation in ruminants

Abstract

There is a need for a better understanding of the mode-of-action of exogenous fibrolytic enzymes (EFE) used as additives in ruminant feeds. Four forages, treated with EFE, were evaluated in vitro and histologically, in an attempt to determine the effect of EFE on tissue degradation. Weeping love grass, kikuyu leaf material, lucerne and wheat straw stem material were histologically evaluated. Simultaneously, milled samples were incubated in the rumen fluid inoculated media for the determination of in vitro digestibility. The main focus, however, was a quantitative assessment of the degradation of the plant tissue at histological level over a 24 h incubation period. Degradation of cell wall components were quantified using the image analysis software. After 12 h of incubation, cell walls of the metaxylem of kikuyu and weeping love grass leaf material were thinner for the EFE treatment than for the control treatment. Treatment also resulted in a significant thinning effect of the cell walls of kikuyu phloem (12 h) and the adaxial epidermis (24 h). The abaxial epidermis at 12 h was thinner for weeping love grass due to EFE treatment. For stem material, a thinning of the epidermis of EFE treated lucerne was observed. Histological findings were concomitant with higher in vitro digestibilities of EFE treated lucerne and kikuyu. It was concluded that image analysis can be useful to quantify changes in cell wall due to the treatment of forages with EFE. There was a definite, subtle thinning effect of EFE on cell wall thickness of plant material which could be indicative of the mode-of-action of EFE.________________________________________________________________________________________________________________________

Use of essential oils in combination with fibrolytic enzymes to decrease in vitro ruminal methane production

“…A fresh batch of dilutions was prepared for each in vitro incubation run. The amount of 400 mg Eragrostis hay was weighed and 1 mL of enzyme or EO treatment was added to each 125 mL serum bottle 24 hours before the start of incubation as pre-treatment of the milled substrate to allow for an enzyme-substrate interaction (Van de Vyver & Cruywagen, 2013). The control treatment received 1 mL of distilled water to standardize the volume of liquor in the vials.…”

“…Although fibrolytic enzymes have been used successfully to improve rumen fermentation with high forage diets (Van de Vyver & Cruywagen, 2013), there is an associated increase in methane production because of a higher proportion of acetate in the fermentation product (Gemeda et al, 2014;Gemeda & Hassen, 2015). In contrast, EOs have been shown to mitigate enteric methane production in vitro and in vivo (Mutavhatsindi et al, 2018).…”

In vitro evaluation of total mixed ration supplemented with exogenous fibrolytic enzymes for crossbred cows

“…The supplementation of exogenous fibrolytic enzymes (EFE) in feeds has been identified as a promising biological treatment to improve the energy availability of feeds to ruminants. Positive effects of EFE include direct hydrolysis, improvement in palatability, changes in gut viscosity, complimentary action with ruminal enzymes, change in the site of digestion [ 2 ], increase in rumen bacterial colonization of the substrate [ 3 ], altering fiber cell wall structures, and thinning of fiber cell wall [ 4 ]. The feeding of diets supplemented with EFE were shown to improve the digestibilities of dry matter (DM), organic matter (OM), crude fiber, neutral detergent fiber (NDF), cellulose and hemicellulose in dairy animals [ 5 - 7 ].…”