Soybean silage as a protein-rich roughage for ruminants: recent advances

Soybean silage has gained attention as a protein-rich roughage for ruminants, particularly in tropical regions where high-quality forage resources are limited. Compared with cereal silages, soybean silage provides higher crude protein. However, it is more difficult to ensile due to low water-soluble carbohydrate content, high moisture content, and high buffering capacity. These characteristics can delay pH decline, increase proteolysis, and lead to variable fermentation quality and animal responses. This review synthesizes recent research on soybean silage, with emphasis on forage characteristics, fermentation biology, management strategies, and implications for ruminant performance under tropical conditions. Soybean silage is most effective as a complementary forage rather than a primary energy source, especially when diets supply adequate fermentable carbohydrates to support ruminal nitrogen utilization. Available studies indicate that harvest timing, moisture control, and the use of additives or microbial inoculants strongly influence fermentation outcomes and nutrient preservation. In particular, the rapid establishment of lactic acid fermentation is critical for limiting protein degradation and improve silage stability. Soybean silage is a valuable option for improving local feed self-sufficiency and reducing reliance on imported protein sources, provided that ensiling practices and dietary integration are appropriately managed. Further refinement of fermentation strategies and farm-scale evaluation will be essential to maximize soybean silage for sustainable ruminant production in the tropics.