Analysis of main factors affecting silage fermentation of sorghum prepared with whole crop and stover in semiarid West Africa

Abstract

Sorghum (Sorghum bicolor L.) is widely cultivated in semiarid West Africa as a combined crop for human consumption and animal feed. In order to address the shortage of ruminant feed in Burkina Faso, we studied the potential of preparing silage from sorghum at  various growth stages and analysed the main factors affecting silage fermentation, including the microbial population, chemical  composition and ensiling characteristics of sorghum prepared with and without microbial additives at three stages of development  (soft dough; hard dough; physiological mature stover). After 90 d of ensiling, lactic acid bacteria (LAB) became the dominant  microorganisms in silages. The silage from soft dough sorghum exhibited the highest LAB counts, water-soluble carbohydrate (WSC) and crude protein content. In addition, silage presented greater quality with higher (p < 0.05) lactic acid content and lower (p < 0.05) pH and ammonia nitrogen levels than those at hard dough stage and stover. The WSC and LAB were the important factors affecting silage fermentation and the addition of LAB and cellulase improved fermentation quality. The combined additives displayed a synergistic effect and when silage is prepared with sorghum at soft dough stage, it has best potential for controlling spoilage microorganisms and preserving the silage quality for animal feed.

Keywords: cellulase, ensiling, fermentation factor, growth stage, lactic acid bacteria