| Ensiling is an effective measure to aviod defoliations caused by the process of hay-making, mildewing when haying at the rainy season and dependence on machine in undeveloped areas. However, hydrolysis and lipolysis occurred in the ensiled alfalfa usually decrease the nutritive values of protein and fatty acid in alfalfa after ensiling. Therefore, inhibition of the lipolysis and proteolysis in ensiled alfalfa will be of great importance in improving the nutritive value of alfalfa silage, and has been a concern at silage field all over the world for a long time.In this study, based on the research advances in inhibiting proteolysis and lipolysis in alfalfa silage, a single factor and completely randomized design was used to investigate the influences of three kinds of pomace(dried apple pomace(AP), unground grape pomace (GP)or ground grape pomace(GGP)), two kinds of antioxidants (apple acid, citric acid) and two kinds of compound additives (apple acid +lactic acid bacteria, citric acid and lactic acid bacteria) on the quality of alfalfa, especially on hydrolysis and the fatty acid composition. In order to provide measures and throretical basis to inhibitting the lipolysis and proteolysis in ensiled alfalfa. A 100 g of the three kinds of pomaces were added respectively to 1 kg of alfalfa silage (Fresh Weight); the apple acid and citric acid were added to alfalfa in concentrations of 0.1%,0.5% and 1% (Fresh Weight); the apple acid and citric acid were added to alfalfa in concentrations of 0.1%,0.5% and 1% together with 106cfu/g lactic acid bacteria. After ensiling for 60 d, we summarised as follows:The results showed that, after adding pomace, the decrease of pH of forage was significant (P<0.05), and the content of lactic acid was increased significantly (P <0.05. However, the aerobic stability was lower than control group. In addition, the nonprotein nitrogen (NPN) concentrations in the ensiled alfalfa were decreased by 54%,67% and 69% after being ensiled with AP, GP and GGP respectively. Total fatty acid concentrations in the control silage and AP silage were comparable, but in GP or GGP-treated silages they were more than double that of the control silage. Because the pomace contains large amounts of oleic acid and linoleic acid, it also led to the oleic acid and linoleic acid contain significantly increased. Compared with AP silage treatment group and the control silage, the content of linoleic acid increased significantly (P<0.05), while the content of linolenic acid decreased significantly (P<0.05) in GP or GGP-treated silages. Comparing with GP-treated silages, the pH and the content of lactic acid in silage treated with ground grape pomace were separately decreased and increased significantly. The processing method of ground grape pomace had better effects on inhibiting proteolysis even though the differences between these two groups were not significant.The pH and dry matter loss were reduced effectively and the amount of carbohydrates was increasesed after adding antioxidants. Meanwhile, addition of apple acid, citric acid could inhibit proteolysis and reduce the amount of NPN (non-protein nitrogen) and NH3-N (ammonia nitrogen). Besides, the effects of the citric acid group were increased significantly with the increase of addtive amount (P <0.05). In terms of the composition of fatty acid, additives had no significant effect on total fatty acid concentrations, but it could increase the amount of polyunsaturated fatty acids effectively (P<0.05), after adding two different kinds of antioxidants, linoleic acid and linolenic acid increased significantly. What’s more, the content of linolenic acid was positively related to the acid content.After adding compound additives, the pH was reduced, and the amount of dry matter and carbohydrates were increased effectively (P<0.05). Addition of compound additives also had a significant effect on inhibition of protein hydrolysis, especially on the content of NH3-N, which treated with 1% malic acid + lactic acid and lactic acid + lactic acid was less than 10% of that in control group. In terms of the composition of fatty acid, the amount of polyunsaturated fatty acids were significantly increased (P<0.05), and the contents of linoleic acid and linolenic acid were improved significantly compared with control group. In the treatment groups added with lactic acid separately, although the contents of linoleic acid and linolenic acid had no significant decrease compared with control group, they were less than that in control group which led to the amount of polyunsaturated fatty acids decreased significantly. |
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