Study on the associative effects of quinoa andsorghum straw under different diet ratios of concentrate to roughage

This study aimed to evaluate the associative effect of different quinoa and sorghum straw ratios under different Concentrate-Roughage ratios. Therefore, the experiment set the concentrate to a roughage ratio of 30 ꞉ 70 and 40 ꞉ 60, respectively, with quinoa straw ꞉ sorghum straw ratios of 40 ꞉ 60 ꞉ 0 (Ⅰ), 40 ꞉ 45 ꞉ 15 (Ⅱ), 40 ꞉ 30 ꞉ 30 (Ⅲ), 40 ꞉ 15 ꞉ 45 (Ⅳ), and 40 ꞉ 0 ꞉ 60 (Ⅴ), as well as 30 ꞉ 70 ꞉ 0 (Ⅵ), 30 ꞉ 55 ꞉ 15 (Ⅶ), 30 ꞉ 40 ꞉ 30 (Ⅷ), 30 ꞉ 25 ꞉ 45 (Ⅸ), 30 ꞉ 10 ꞉ 60 (Ⅹ), 30 ꞉ 0 ꞉ 70 (Ⅺ). The combination ratios of the 11 mixed feeds, along with the separate concentrates, and quinoa straw and sorghum straws as controls were used during in vitro gas production experiments that were conducted to determine the in vitro dry matter degradation rate (IVDMD), rumen fluid pH, and total volatile fatty acids (TVFA) of the different diet combinations. Moreover, the ammonia nitrogen (NH₃-N) content was also investigated and the single and multiple factors associative effect indices were calculated for each feed combination. The results showed that the GP of all groups increased significantly within 24 h, then leveled off, except for the fermentation time. The IVDMD increased with an increase in the sorghum straw addition. When the ratio of concentrate to roughage was 40 ꞉ 60, the GP_{24 h}, the NH₃-N content, and the total volatile fatty acid (TVFA) increased by 36.2% and 53.5%, 30.7% and 30.3%, and 12.2% and 33.3%, respectively. Moreover, the single factor associative effect index (SFAEI) of the NH₃-N and TVFA in group Ⅲ were significantly higher than those in other groups(P < 0.05), and the multiple factors associative effect index (MFAEI) in the same group (Ⅲ) was significantly higher than that in other groups (P < 0.05). When the ratio of concentrate to roughage was 30 ꞉ 70, the GP_{24 h}, the NH₃-N content, and the TVFA increased by 29.2 and 23.2%, 35.1% and 2.06%, and 32.7 and 16%, respectively. Compared with the single quinoa and sorghum groups, the SFAEI of the TVFA in group Ⅷ was significantly higher than that in the other groups (P < 0.05). Moreover, the SFAEI of the NH₃-N in groups Ⅷ and Ⅺ were significantly higher than in group Ⅵ (P < 0.05), and the MFAEI in group Ⅷ was significantly higher than in groups Ⅵ, Ⅸ, and Ⅹ (P < 0.05). In conclusion, the MFAEI of the concentrate ꞉ quinoa straw ꞉ sorghum straw was 30 ꞉ 40 ꞉ 30, which was the largest. It could be used as an optimal feed combination and a suitable additive amount in the production practice.