Abstract:

This research used in vitro gas production （GP） when feed samples were incubated with rumen fluid of donor Han sheep， to explore the optimal associative effects （AE） when mixing maize （Zea mays） straw silage， feed concentrate， and commercial waste and peel of one of three different vegetables： mung bean （Vigna radiata）， garlic （Allium sativum）， or eggplant （Solanum melongena）. First， the different vegetable wastes were screened as mixtures with maize straw silage at ratios of 100∶0， 75∶25， 50∶50， 25∶75， 0∶100. For each vegetable waste， the maize straw silage mixture with the best AE was regarded as a mixed roughage that was combined with a commercial concentrate at ratios of 0∶100， 50∶50， 60∶40， 70∶30， 80∶20， 100∶0. The GP was recorded at 0， 2， 4， 6， 9， 12， 24， 36， 48， 72 hours. From exponential curve fitting of the GP time series data， the fast GP， slow GP， and an exponential GP constant were calculated. The GP_72h and weighted estimated values of each combination were used to calculate the value of AE of GP. The results showed that the AE value were significantly or extremely significantly higher （P<0.01， P<0.05） than the other two groups when peel of mung bean， garlic or eggplant was combined with maize straw silage at ratios of 25∶75， 75∶25， 50∶50， respectively. When these three mixed roughages were combined with concentrate at different ratios， for the 25∶75 mung bean waste： maize straw silage it was found that the fast GP， the AE of GP at 48 and 72 hours of 70∶30 ratio were significantly higher than 80∶20， 60∶40， 50∶50 groups （P<0.05）. For the 75∶25 garlic peel∶maize silage mixed roughage， the slow GP and potential GP of the 60∶40， 0∶100 concentrate groups were significantly or extremely significantly higher than 100∶0， 80∶20 and 50∶50 groups （P<0.05， P<0.01）. Also， the AE value of GP at 48 and 72 hours of 60∶40 concentrate mixture of garlic peel mixed roughage were significantly higher than the other three groups （P<0.05）. For the eggplant peel mixed roughage， the 80∶20 mixture with concentrate had a significantly higher fast GP and AE value of GP at 48 and 72 hours than the other three groups （P<0.01， P<0.05）. In summary， optimal dietary AE was obtained with a 17.5∶52.5∶30.0 ratio of mung bean peel∶corn straw silage∶concentrate； with a 45∶15∶40 ratio of garlic peel∶corn straw silage∶concentrate； and with a 40∶40∶20 mixture of eggplant peel∶corn straw silage∶concentrate. However， a caveat is that these in vitro results still need to be validated by animal feeding experiments to confirm that they hold good for predicting the performance of animals.

Key words: mung bean peel, garlic peel, eggplant peel, corn straw silage, concentrate, associative effects, in vitro gas production method