Effects of different storage times on the nutritional quality and amino acid profile of alfalfa hay

The purpose of this study was to determine and comprehensively evaluate the dynamic changes in nutrient contents and composition of amino acids in alfalfa hay during storage. We used ‘Bara310SC’ as the experimental material to prepare hay after harvest at the early flowering stage, and determined the nutritional quality and amino acid compositions after 30, 60, 90, and 120 days of storage. The results revealed that the nutritional quality of alfalfa hay declined with an increase in storage time. Whereas the content of crude protein and relative feeding value of alfalfa hay declined gradually over time, the contents of acid detergent fiber, neutral detergent fiber, and crude ash underwent a gradual increase. In addition, we detected 17 types of amino acids in alfalfa hay, and found that the contents of these amino acids declined with an increase of storage time. The contents of total amino acids, essential amino acids, and non-essential amino acids all declined with an increase in storage time, as did the contents of functional amino acids. Furthermore, we established that the ratio coefficient of amino acids was highest after 30 days of storage. In addition, the content of crude protein was found to be positively correlated with that of proline, isoleucine, leucine, tyrosine, histidine, and arginine (P < 0.05), and was highly positively correlated with alanine, cystine, phenylalanine, and lysine (P < 0.01). Moreover, we identified a more complex correlation among the compositions of amino acids. Combined with the membership function analysis method of fuzzy mathematics, we established that the best quality hay was that which had been stored for 30 days. In conclusion, the quality of alfalfa hay was found to decline with an increase in storage time. Therefore, to ensure a desirable quality of alfalfa hay to feed livestock and to reduce the loss of nutrients, the storage time should, as far as possible, be limited to within 30 days, to achieve efficient feeding results.