In vitro rumen fermentation performance in mutton sheep for three kinds of wrapped-silage forage from the hill and gully region of the Loess Plateau

To evaluate the fermentation performance of different wrapped silage forage in mutton sheep rumen by using the in vitro fermentation gas production method, three kinds of wrapped silage were selected as experimental material from the hill and gully region of the Loess Plateau. The results showed no significant differences in cumulative gas production between corn (Zea mays) silage and oat (Avena sativa) silage (P > 0.05); however, the cumulative gas production of both silages was significantly higher than that for alfalfa (Medicago sativa silage) (P < 0.05). There was no significant difference in gas production rate (c) among the three kinds of wrapped silage (P > 0.05). There was no significant difference in partial gas production (b), potential gas production (a + b), and 48 h cumulative gas production (GP) between corn silage and oat silage (P > 0.05); however, these were significantly higher than that for alfalfa silage (P < 0.05). Ammonia nitrogen (NH₃-N) concentration and metabolic energy (ME) were not significantly different between corn silage and oat silage (P > 0.05). The NH₃-N concentration of corn silage and oat silage was significantly higher than that for alfalfa silage (P < 0.05); however, the ME was significantly lower than that for alfalfa silage (P < 0.05). There was no significant difference in the pH and in vitro dry matter disappearance rate (IVDMD) of the three kinds of wrapped silage forage (P > 0.05). Furthermore, there was no significant difference in total volatile fatty acid (TVFA) concentration and the butyric acid ratio between the three kinds of silage forage after 48 h fermentation in vitro (P > 0.05). The ratio of acetic acid and acetic/propionic (A/P) of alfalfa silage were significantly higher than that of corn and oat silage (P < 0.05); however, the propionic acid ratio of alfalfa silage (15.95%) was significantly lower than that of corn (23.98%) and oat (24.43%) (P < 0.05) silage. In summary, GP, dry matter digestibility, and ME in vitro of gramineous forage (corn and oat wrapped-silage) were higher than that of leguminous forage (alfalfa wrapped silage). However, the NH₃-N and TVFA concentration of alfalfa wrapped silage was higher than that of gramineous (corn and oat wrapped-silage) forage.