Effects of the gender differences in cattle rumen fermentation on anaerobic fermentation of wheat straw

The rumen anaerobic fermentation has been exploited as a molecular platform for producing fermentative biogas and organic acids. The aim of this study was to select more efficient rumen fermentation bacteria by comparing the nutrient degradation rate, rumen fermentation characteristics and bacterial flora between the bulls and heifers. The rumen fluid from bulls and heifers was inoculated to wheat straw for anaerobic fermentation to produce organic acids and biogas. The results showed that the bulls had higher degradation rate of dietary total solids and acid detergent fiber, and had higher concentration of acetate, butyrate, ammoniacal nitrogen, total volatile fatty acids and total fungi in rumen compared with the heifers (P < 0.05). The rumen bacterial flora of bulls had lower the shannon index, and higher bacterial abundance of Bacteroidia class and Prevotellaceae family than that in the rumen of heifers (P < 0.05). These bacterial floras were significantly clustered according to gender (P < 0.05). There were significant correlations between the abundance of rumen bacteria families and the rumen fermentation products. In the anaerobic fermentation of wheat straw, the wheat straw inoculated with bull rumen fluid produced 183.4 mmol of acetate, 22.19 mmol of propionate, 221.6 mL/g volatile solid (VS) of biomethane and 44.6 mL/g VS of biohydrogen, which were 16.8%, 39.3%, 32.5% and 46.8% higher than those inoculated with heifer. The methane potential yield model shown that bull microbes produced 288 mL/g VS maximum methane yield, increased by 35.2% compared to heifers. These results suggested that the differences in the rumen bacterial flora between different genders of the cattle resulted in the rumen bacteria from bulls were more conducive to the production of biofuels and bioproducts by anaerobic fermentation.