Abstract: This study evaluated the effect of the cutting date and growth stage at cutting on nutritional quality and fermentation characteristics of alfalfa of [147 regiment] in Shihezi city, Xinjiang. Data were collected for the first, second and third cuts of the season, for bud, early flowering, and flowering crop growth stages. Silage quality was determined by sampling at 3, 9, 15, 30, 45 and 60 days after commencement of silage fermentation. Highly significant (P<0.01) effects of cutting date on crop growth duration, dry matter yield, neutral detergent fiber, crude protein, lactic acid and acetic acid contents of silage were observed. In alfalfa the silage fermentation process can reduce nutrient content. After 60 days fermentation, DM content of alfalfa silage in the third cutting was the highest, reaching 39.03%. Acid and neutral detergent fiber contents were lowest in the third cut at the budding crop growth stage, while crude protein contents were highest in the first cut at budding stage. CP and WSC were the highest in the first cutting, which was 20.21% and 4.39%, respectively. The highest silage lactic and acetic acid contents occurred in second cut silage harvest at the budding stage. The ammonia nitrogen content of silage from the first cut was the lowest at the budding stage. The earlier the cutting time, the more tender the alfalfa crop was, and the higher the nutritive quality and palatability was, and plant regrowth was also improved. The overall ranking of cut and growth stage combinations for silage nutritive value, quality and yield was: first cut at bud stage>third cut at bud stage>first cut at early flowering stage>second cut at bud stage>third cut at early flowering stage>first cut at flowering stage>third cut at flowering stage>second cut at early flowering stage>second cut at flowering stage. Therefore, controlling the cutting time of alfalfa could improve the nutrition, fermentation quality and utilization rate of alfalfa.

Key words: alfalfa silage, nutritional quality, fermentation quality, growth period