Abstract
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.