Candida tropicalis as a novel dietary additive to reduce methane emissions and nitrogen excretion in sheep.

Abstract

The goal of this study was to investigate Candida tropicalis as a kind of environmentally friendly dietary additive to manipulate ruminal fermentation patterns, reduce methane emissions and nitrogen excretion, and to screen the appropriate dose for sheep. Twenty-four Dorper × thin-tailed Han crossbred ewes (51.12kg ± 2.23kg BW) were selected and randomly divided into four groups which were fed Candida tropicalis at dose of 0 (control), 4 × 108 (low dose), 4 × 109 (medium dose), and 4 × 1010 (high dose) colony-forming units (CFU)/d per head, respectively. The experiment lasted 33days with 21days for adaptation and 12days for nutrient digestibility trial and respiratory gases sampling. The results showed that nutrients intake was not affected by Candida tropicalis supplementation (P > 0.05), whereas apparent digestibility of nutrients significantly increased compared with the control group (P < 0.05). Nitrogen and energy utilization increased with Candida tropicalis supplementation (P < 0.05). Compared with the ewes of the control group, rumen fluid pH and NH3-N concentration were not affected (P > 0.05), whereas total volatile fatty acid concentration and molar proportion of propionate were greater (P < 0.05), and molar proportion of acetate and the ratio of acetate to propionate were less (P < 0.05) when the ewes were fed Candida tropicalis. Daily total CH4 production (L/d) and CH4 emissions yield (L/d of CH4 per kg of dry matter intake, metabolic weight, or digestibility dry matter intake) were decreased at the low dose group (P < 0.05). The abundance of total bacteria, methanogen, and protozoa in rumen fluid was significantly higher at medium dose and high dose of Candida tropicalis supplementation (P < 0.05) compared with low dose and the control group. In summary, Candida tropicalis supplementation has a potential to reduce CH4 emissions and nitrogen excretion, and the optimal dose should be 4 × 108CFU/d per head.