Influence of an anaerobic fungal culture administration on in vivo ruminal fermentation and nutrient digestion

Abstract

Experiments were conducted to study the effect of administration of anaerobic fungal cultures or their enzymes on ruminal fermentation, microbial populations and enzyme activities in the rumen, and general nutrient digestion in sheep. Twelve mature sheep receiving 560 g of orchard grass hay and 240 g of concentrate per day were randomly assigned to three different treatments with four sheep per treatment. Control (FM) animals received 200 ml of the defined medium for fungal growth through rumen cannulae at 8.00 h each day (as a control treatment without added fungal enzymes and viable cells). The second group of animals (FE) were given 200 ml of supernatant from fungal culture incubated with an anaerobic ruminal fungus for 7 days (as a treatment for fungal enzymes in cultures without viable fungus). The third group (FC) was administered with an anaerobic fungal culture incubated for 7 days (as a direct-fed microbials (DFM) treatment with fungal enzymes and viable cells). Animals were exposed to each treatment for 15 days before rumen collection and digestion trials began. Direct administration of cultures of a polycentric fungal strain, Orpinomyces strain KNGF-2 isolated from a Korean native goat, to the rumen of sheep (FC) generally increased nutrient digestibility and nitrogen (N) retention resulting from an increase in numbers of bacteria and fungi in the rumen and by altering the patterns of volatile fatty acids (VFA) production. However, administration of fungal enzyme (FE) failed to improve nutrient digestibility and N retention, and ruminal fermentation parameters. Results indicate that these proteins may be rapidly degraded by ruminal microbes or that these enzymes could reduce the growth or activity of ruminal microbes. These are the first report of the effect of DFM originating from an anaerobic fungal culture. Such a development is particularly significant because this study demonstrates that the introduction of a microorganism with superior fibrolytic activity into the rumen can improve nutrient utilization in ruminants.