Effects of Processing Methods and Inclusion Levels of Dried Garlic on In Vitro Fermentation and Methane Production in a Corn Silage-Based Substrate.

Garlic ( Allium sativum ) contains secondary compounds that are known to modify rumen fermentation parameters and decrease methane (CH 4 ) emissions. The objective was to evaluate the effects of increasing the inclusion levels and processing methods of garlic on in vitro fermentation and CH 4 production. Treatments were arranged in a randomized complete block design with a 2 × 3 × 2 + 1 factorial arrangement, where the main factors were the initial condition of garlic (intact or smashed), drying process (freeze-dried, oven-dried, or autoclaved), and garlic proportion in the diet (2.5 and 5%) and one control (without garlic supplementation). Incubations were conducted using corn silage and cotton-gin trash (80:20, respectively) as basal substrates on three different days. Final pH, the concentration of volatile fatty acids (VFA) and ammonia nitrogen (NH 3 -N), in vitro organic matter digestibility (IVOMD), total gas production, and CH 4 concentration were determined after 24 h. Initial garlic condition or drying processing neither modify ( p > 0.05) the in vitro fermentation nor the CH 4 production. However, increasing garlic inclusion linearly increased ( p < 0.05) IVOMD, the concentration of the total VFA, and the proportion of propionate. Also, the concentration of NH 3 -N and the proportion of acetate increased quadratically ( p < 0.05) with greater garlic inclusions. Finally, garlic inclusion did not affect ( p > 0.05) gas and CH 4 production. In conclusion, increasing garlic levels, but not the processing methods, improved in vitro fermentation but did not modify CH 4 emissions under in vitro conditions.