Effects of prefermented cereal-derived substrates (ground barley and rye bran) enriched with fungal γ-linolenic acid on rumen fermentation parameters and lipid metabolism in vitro

Aims: To increase rumen output of γ‐linolenic acid (GLA), we used two cereal‐derived substrates, ground barley (GB) and rye bran (RB), enriched with fungal GLA as components of feed rations. We examined their effects on rumen fermentation patterns, lipid metabolism and the ciliated protozoan population in an artificial rumen. Methods and Results: Four diets consisting of meadow hay (MH) plus unfermented (GB or RB) or prefermented (GB ? TE or RB ? TE) cereal‐derived substrates were fermented in an artificial rumen with ovine rumen inoculum. The cereal‐derived substrates were prefermented with the fungus Thamnidium elegans (TE) by fungal solid‐state fermentation. The diets with TE increased the rumen input of dietary GLA (mg day^?1) from 0 to 21 (GB ? TE) or 26 (RB ? TE). Both experimental diets increased the rumen output of GLA (P < 0·001). Adverse effects on the ciliate population were observed. Both diets also had an effect on the fatty acids profile. Fermentation patterns were also affected with MH + RB ? TE. Conclusion: Cereal‐derived substrates enriched with GLA effectively enhanced the output of GLA in artificial rumen. Significance and Impact of the Study: The ability of the fungal strain T. elegans to grow and utilize various agro‐industrial substrates might be useful in developing potential new animal diets enriched in GLA.