RESUMO
BACKGROUND: The present study explored the effect of garlic and/or eucalypt oils on biogas production during in vitro ruminal fermentation of four agro industry byproducts. For this, 0-180 mg oil L-1 incubation medium was added and gas volumes were recorded from 2 to 48 h of incubation. Dry matter substrate degradability and neutral as well as acid detergent fibre were determined after 72 h. RESULTS: Gas production and nutrient degradability was oil type dependent. The oils enhanced (P < 0.05) biogas and asymptotic biogas production for corn stalks and oat straw, although no effect was observed on asymptotic biogas production for sorghum straw and sugarcane bagasse. Addition of both oils decreased (P < 0.05) fermentation pH for corn stalks, sorghum straw and oat straw and also increased (P < 0.05) dry matter degradability for all four byproducts. Neutral detergent fibre degradability for all byproducts was higher (P < 0.05) with garlic oil. Eucalypt oil, however, decreased (P < 0.05) neutral detergent fibre degradability for sugarcane bagasse and corn stalks, although only weak effects were observed for sorghum and oat straws. CONCLUSION: With respect to ruminal biogas production, the addition of garlic oil showed better environmental effects than the addition of eucalypt oil and increasing oil concentrations resulted in enhanced fermentation characteristics. © 2018 Society of Chemical Industry.