Effects of Schizochytrium microalgae and sunflower oil as sources of unsaturated fatty acids for the sustainable mitigation of ruminal biogases methane and carbon dioxide

Biogases produced during ruminant production needs to be reduced. The Food and Agriculture Organization (FAO) estimated CH4 production from livestock to contribute about 18% of all greenhouse gas emissions, while carbon dioxide (CO2) accounted for about 9% of the emission (FAO, 2006). Besides, these gases including CH4, CO2, and H2 are produced during ruminal fermentation and cause losses amounting to 2e12% of dietary energy in ruminants (Johnson and Johnson, 1995). Furthermore, these emissions have been implicated in causing climate change. Yeast, organic acids salt, exogenous enzymes, and essential oils have been used as new strategies to mitigate the production of ruminal methane from ruminants (Elghandour et al., 2016, 2017; Hernandez et al., 2017).Mitigation of methane (CH4) and carbon dioxide (CO2) emissions as well as ruminal fermentation parameters of a total mixed ration in the presence of Schizochytrium microalgae (SA) and sunflower oil (SO) or their mixture (SASO) as unsaturated fatty acid sources was investigated. Rumen liquor from two rumen cannulated Holstein steers and two rumen cannulated Creole goats was used as inoculum. Interactions between inoculum source additive type, and inoculum source additive type dose were observed for gas, CH4 and CO2 production and fermentation parameters. Additives affected the fermentation parameters in a dose-dependent manner. With goats’ inoculum, the inclusion of SO (1, 2, 4, 5%), SA (2, 3, 5%) and SASO (1, 3%) increased gas production (GP) and decreased the rate of GP, while with the steer inoculum, SO at 1 and 4% increased GP and the rate of GP. All levels of SA and SASO decreased the asymptotic GP and increased the rate of GP. The goat inoculum decreased CH4 at different doses of SO, SA and SASO whereas the steer inoculum decreased CH4 production. At all doses, additives decreased fermentation pH, protozoal counts, and increased ammonia-N, DM degradability and total bacterial counts. Sunflower oil (i.e., SO) at 1e3%, SA at 1e2%, and SASO at 1e2% were the most efficacious in the nutrition of goats, compared with SO at 1 to 2 in steers. The results suggest that Schizochytrium microalgae and sunflower oil could be a valuable means of sustainably mitigating CH4 and CO2 emissions for improved environmental conditions