Associative effects of corn straw silage with beet root on fermentation by the in vitro gas production method

This study was conducted to analyze the associative effects of corn straw silage (Zea mays) with beet root (Beta vulgaris) on fermentation parameters in vitro. Corn straw silage was combined with beet rootat ratios of 100 ꞉ 0 (T₁), 80 ꞉ 20 (T₂), 60 ꞉ 40 (T₃), 50 ꞉ 50 (T₄), 40 ꞉ 60 (T₅), 20 ꞉ 80 (T₆), and 0 ꞉ 100 (T₇). We usedin vitro rumen fermentation technology to analyze the nutrient degradation rate, fermentation parameters, and total gas production, to evaluate the combined effect on rumen fermentation in vitro. The results showed thefollowing: 1) as the proportion of beet root increased, DMD (dry matter degradability), NDFD (neutral detergent fiberdegradability), and ADFD (acid detergent fiberdegradability) first increased and then decreased, and the nutrient degradation rate after combination was higher than that of a single raw material; 2) as the proportion of beet root increased, the pH decreased gradually, and the pH of the T₁ group was significantly higher than that of the other groups (P < 0.001).The concentration of NH₃-N in the T₃ and T₆ groups was significantly lower than that in the other groups (P = 0.003). When the proportion of beet rootswas 40%, the concentrations of TVFAs (total volatile fatty acids) and each volatile fatty acid were the highest, and when the proportion of beet root was more than 40%, the concentration showed a decreasing trend, and the acetate/propionate values of the T₃, T₄, and T₅ groups were significantly higher than those of other groups (P < 0.001); 3) fermentation time had a significant effect on total gas production (P < 0.001), and the time and treatment had significant interaction effects (P = 0.006). As the fermentation time increased, the total gas production increased gradually, and with the increase in the proportion of beet root, it first increased and then decreased. After fermentation for 4, 8, and 12 h, the total gas production inthe T₃ group was significantly higher than that inthe T₁, T₆, and T₇ groups (P < 0.004), and after fermentation for 24 and 48 h, the total gas production in group T₄ was significantly higher than that ingroups T₆ and T₇ (P < 0.008); and 4) the single-factor associative effects index of different proportions were different, but from the multiple-factor associative effects index, the result was T₃ > T₅ > T₄ > T₂ > T₆. Therefore, the optimal combination of corn straw silage and beet root was 60 ꞉ 40.