PS9-18. Enteric Methane Emissions in Mature Spanish Goats as Affected by Red Algae (Asparagopsis taxiformis), Concentrate Level, and Forage Type.

Abstract Reducing enteric methane (CH4) production may improve energy efficiency and overall productivity in small ruminants. The objective of this study was to evaluate the effects of red algae (Asparagopsis taxiformis), concentrate inclusion level, and forage type on methane emissions in meat goats. Thirty-six mature Spanish goats were assigned to a split-plot design comprising 12 simultaneous 3 × 3 Latin squares, with three 3-week experimental periods. Dietary treatments included three levels of red algae supplementation (0, 2, and 4 g/day). Two concentrate inclusion levels (20% and 30% of total dry matter intake [DMI]) were used, with the remainder of the diet supplied as forage (alfalfa, bermudagrass, or mixed grass hay). Forage and concentrate combinations were formulated to meet maintenance energy requirements and provide approximately 10% crude protein. Methane concentration (ppm) was measured using a portable laser methane detector (LMD), whereas methane production (RC-CH4; g/day) was measured using standard respiration calorimetry (RC) over a 24-h period during week 3. Data were analyzed using the MIXED procedure of SAS, with algae level, concentrate level, forage type, and their interactions as fixed effects, and animals nested within Latin squares as random effects. Supplementation with red algae significantly reduced both LMD-CH4 and RC-CH4 expressed per kilogram of DMI (P < 0.003). Goats receiving 2 and 4 g/day of algae exhibited reductions of 41% and 55% in LMD-CH4 (18.9 and 14.3 ppm/kg DMI, respectively) and 35% and 74% in RC-CH4 (18.6 and 7.4 g/kg DMI, respectively), relative to the control (32 ppm/kg DMI for LMD-CH4 and 28.2 g/kg DMI for RC-CH4). Forage type significantly influenced LMD-CH4 and RC-CH4 per kilogram DMI (P < 0.05), with mixed grass hay diets resulting in higher methane production than Bermuda or alfalfa hay diets (24.9, 19.9, and 20.5 ppm/kg DMI for RC-CH4 and 19.4, 16.8, and 18.3 g/kg DMI for LMD-CH4, respectively). The main effect of concentrate inclusion levels on methane emissions per kilogram DMI was not significant for both RC-CH4 and LMD-CH4; however, the forage type × concentrate level and the algae × forage type interactions were significant (P < 0.05) for RC-CH4 but not for LMD-CH4. In conclusion, red algae supplementation substantially reduced CH4 emissions per kilogram DMI in goats, with reductions exceeding 50% at higher inclusion levels. Forage types also contributed to variation in methane production. These findings also highlight the combined potential of red algae supplementation and forage selection as effective nutritional strategies to mitigate enteric methane emissions in meat goat production systems.