Substrates enriched by the fungus Cunninghamella echinulata: an in vitro study of nutrient composition, sheep rumen fermentation and lipid metabolism.

Abstract

Enrichment of wheat bran (WB), corn meal (CM) and barley flakes (BF) with the oleaginous fungus Cunninghamella echinulata (CE) might lead to effective use of these by-products in ruminant nutrition. We examined their effects on rumen fermentation and lipid metabolism. WB, CM and BF substrates without or with brewer's grains (WBG, CMG, BFG) and enriched with CE were incubated with meadow hay (MH, 500 : 500, w/w) in rumen fluid in vitro for 24 h. The dry matter of the CE-enriched substrates increased (by 2-4%); however, digestibility decreased (P < 0·01). Adverse effects of CE-enriched substrates on the rumen ciliate population were observed. Little effect on the rumen eubacterial population was detected by the 16S-polymerase chain reaction/denaturizing gradient gel electrophoresis method. The increase in γ-linolenic acid output in the MH + BFGCE diet (800 : 200, w/w) was accompanied by an increase in rumen biohydrogenation of polyunsaturated fatty acids. The diet substrates enriched with the fungus CE were less digestible than the untreated cereal substrates; no appreciable positive effect was observed on rumen fermentation patterns or the eubacterial and ciliate populations. The in vitro study showed that adding CE-enriched substrates to ruminant diets is not effective for improving rumen fermentation.