Ruminal Methanogenic Responses to the Thiamine Supplementation in High-Concentrate Diets

SIMPLE SUMMARY: Optimal methane (CH(4)) mitigation strategy should decrease carbon footprint and meanwhile avoid causing hazard residues and productive reduction. Thiamine is a critical coenzyme in carbohydrates, and metabolism has been confirmed to effectively attenuate subacute ruminal acidosis (SARA). Whether thiamine supplementation impacts ruminal methanogenesis is still unclear. In the present study, thiamine supplementation in high-concentrate diets (HC) was conducted to investigate the impacts on ruminal methanogenesis process. Results indicated that thiamine supplementation in HC could efficiently reduce CH(4) emissions compared with high-forage diets; meanwhile, it did not cause ruminal metabolic disorders compared with HC treatment. The effective decrease in methane production and changes of methanogens after thiamine supplementation in HC compared with high-forage diets contributed a better understanding of thiamine on ruminal carbohydrate metabolism. This finding here provided a brand-new perspective on mitigating methane emission in dairy cattle production, and an optimal strategy to decrease the carbon footprint without compromising the livestock production efficiency. ABSTRACT: Background: Thiamine supplementation in high-concentrate diets (HC) was confirmed to attenuate ruminal subacute acidosis through promoting carbohydrate metabolism, however, whether thiamine supplementation in HC impacts methane metabolism is still unclear. Therefore, in the present study, thiamine was supplemented in the high-concentrate diets to investigate its effects on ruminal methanogens and methanogenesis process. Methods: an in vitro fermentation experiment which included three treatments: control diet (CON, concentrate/forage = 4:6; DM basis), high-concentrate diet (HC, concentrate/forage = 6:4; DM basis) and high-concentrate diet supplemented with thiamine (HCT, concentrate/forage = 6:4, DM basis; thiamine supplementation content = 180 mg/kg DM) was conducted. Each treatment concluded with four repeats, with three bottles in each repeat. The in vitro fermentation was sustained for 48h each time and repeated three times. At the end of fermentation, fermentable parameters, ruminal bacteria and methanogens community were measured. Results: HC significantly decreased ruminal pH, thiamine and acetate content, while significantly increasing propionate content compared with CON (p < 0.05). Conversely, thiamine supplementation significantly increased ruminal pH, acetate while significantly decreasing propionate content compared with HC treatment (p < 0.05). No significant difference of ruminal methanogens abundances among three treatments was observed. Thiamine supplementation significantly decreased methane production compared with CON, while no significant change was found in HCT compared with HC. Conclusion: thiamine supplementation in the high-concentrate diet (HC) could efficiently reduce CH(4) emissions compared with high-forage diets while without causing ruminal metabolic disorders compared with HC treatment. This study demonstrated that supplementation of proper thiamine in concentrate diets could be an effective nutritional strategy to decrease CH(4) production in dairy cows.