Effect of corn stalks treated with carbonylamines in different concentrate and forage rations and nitrogen conditions on rumen fermentation in vitro.

[Objective] To investigate the effects of concentrate/roughage ratios and nitrogen levels on in-vitro rumen fermentation of urea-treating corn stalk. [Method] The concentrate/roughage ratios were 7∶3, 5∶5 and 3∶7. The crude protein levels were 11% and 14%. The in-vitro culture time was 2, 4, 6 and 48 h. [Result] The pH value of broth decreased significantly with the decline in the proportion of roughage (P 0.01) and with the increase in the crude protein levels (P 0.05). The ammonium nitrogen concentration and acetic acid/propionic acid ratio of the fermented products decreased with the increase in the crude protein levels and proportion of concentrate in diet. The diet with concentrate/roughage ratio of 5∶5 and crude protein level of 14% had significantly higher digestibility of dry matter and organic matter than other diets (P 0.05). The digestibility of organic matter increased gradually with the increasing proportion of concentrate and crude protein level. With the increase in the proportion of concentrate, the microbial protein levels increased remarkably, while the acetic acid/propionic acid ratio declined. [Conclusion] The concentrate/roughage ratios and nitrogen levels affect rumen fermentation and microbial growth during in-vitro culture. However, the best supplementary feeding results of urea-treating corn stalks can be obtained when the concentrate/roughage ratio is below 5∶5 and the crude protein level is 14%.