Sustainable mitigation of fecal greenhouse gases emission from equine using safflower and fish oils in combination with live yeast culture as additives towards a cleaner ecosystem

Abstract

This study was investigated to determine the synergistic effect of dietary oils (safflower and fish oils) and yeast on in vitro biogases emission from horses fed with concentrate forage. Fecal from adult English Thoroughbred horses were used as inoculums source in this study. Oils of safflower and fish were supplemented at two different concentrations (2.4 and 4.8% v/w), while Saccharomyces cerevisiae was supplemented at 4 mg/g dry matter (DM) into the diet. The asymptotic gas production (GP), rate of GP, and lag period were not affected due to the supplementation of safflower oil, fish oil, and S. cerevisiae. The oil level × S. cerevisiae interaction showed significant (P = 0.047) mitigation of asymptotic methane (CH4) emission. In contradictory, additives revealed no influence on asymptotic, rate, and lag time of carbon dioxide (CO2) and hydrogen (H2) productions. The fermentation pH was unaffected, while dry matter degradability (DMD) was decreased (P < 0.05) due to the supplementation of additives. Further, additives increased (P < 0.05) in vitro GP up to 48 h. The safflower oil, fish oil, and S. cerevisiae revealed significant (P < 0.05) impact on mitigating CH4 emission. Both the oils and S. cerevisae showed non-significant influence on CO2 emission (mL/0.5 g DM incubated), while CO2 emission (mL/0.5 g DM degraded) was reduced (P ≤ 0.05) due to oil type × S. cerevisiae and oil level × S. cerevisiae interactions. Likewise, oil type × S. cerevisiae interaction revealed significant (P < 0.05) mitigation in H2 production (mL/0.5 g DM degraded) up to 12 h of incubation. Concisely, dietary oils and yeast can be implied as dietary manipulation strategy for mitigating in vitro CH4, CO2, and H2 emission from horses. The combination of safflower oil, fish oil, and yeast could undeniably be a prominent feeding approach for livestock towards the maintenance of cleaner ecosystem.