PSVI-19 - Effect of Processing Methods and Inclusion Level of Dried Raw Garlic on in vitro Fermentation Profile and Methane Production in a Corn Silage-based Diet

Abstract: Garlic (Allium sativum) contains secondary compounds known to modify rumen fermentation parameters and decrease methane (CH₄) emissions; however, results from previous research on the effects of garlic-byproduct supplementation are quite variable. The objective of this experiment was to evaluate the effects of increasing inclusion levels and processing methods of dried raw garlic on in vitro ruminal fermentation and CH₄ production. The experiment was designed as a randomized complete block design, where 24 h incubations were conducted on three separate days, with corn silage and gin trash (80:20, respectively) used as basal substrate. Treatments were arranged in a 3 × 3 factorial with garlic inclusion (0, 2.5, and 5% of the diet) and processing method (freeze-dried, oven-dried, and autoclaved) as factors. Three ruminally cannulated steers were fed ad libitum a corn silage and gin trash diet, for at least 35 d prior to collection of ruminal fluid used as inoculum. Final pH, concentration of volatile fatty acids (VFA) and ammonia nitrogen (NH₃-N), in vitro organic matter digestibility (IVOMD), total gas production, and CH₄ concentrations were determined at the end of incubation. Data were analyzed using the Mixed procedure of SAS. Final pH and concentration of total VFA were not affected (P > 0.05) by the processing method nor inclusion level of garlic. Increasing garlic inclusion decreased NH₃-N concentration (P < 0.05), reduced (P < 0.05) the proportion of acetate, tended to increase (P < 0.10) the proportion of propionate, and tended to decrease (P < 0.10) the acetate:propionate ratio. Neither garlic inclusion level nor processing methods modified IVOMD, total gas production, or CH₄ concentration. Modifications in VFA molar proportions and NH₃-N concentration may be related to differences in N concentration in the incubated substrates. In conclusion, neither processing method nor garlic level inclusion modified CH₄ production or nutrient digestibility.