Study on the dynamic changes of long-chain fatty acids in alfalfa silage during aerobic exposure
The objective of this study was to investigate the dynamic changes of fermentation characteristics,nutrient content and long-chain fatty acids,including palmitic acid,palmitoleic acid,stearic acid,oleic acid,linoleic acid and linolenic acid,in alfalfa silage during aerobic exposure by a small bag silage method.The results showed that lactic acid content of alfalfa silage was sig-nificantly decreased during aerobic exposure(P＜0.05),while pH value,acetic acid content,propionic acid content,butyric acid content and ammonia nitrogen content in total nitrogen were significantly increased(P＜0.05).Compared with raw alfalfa,the contents of dry matter,crude protein,acid detergent fiber and water soluble carbohydrates in silage were significantly de-creased,and the contents of dry matter and crude protein continued to decrease during aerobic exposure(P＜0.05).The con-tents of palmitic acid,linolenic acid and linoleic acid in raw alfalfa and silage was more than 1 mg/g,while the contents of palmitoleic acid,stearic acid,and oleic acid were low,and without obvious change during whole process.Contents of palmitic acid and linolenic acid increased during anaerobic fermentation.The content of palmitic acid did not change but linolenic acid decreased during aerobic exposure.The total long-chain fatty acid content in alfalfa silage was significantly increased during an-aerobic fermentation(P＜0.05),but decreased after it exposed to air,and reached even lower than that in raw alfalfa(P＜0.05).In conclusion,the quality of alfalfa silage was obviously deteriorated during aerobic exposure,and the long-chain fatty acid accumulated in the anaerobic fermentation were gradually consumed.
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