Nutritional Efficiency of Mulberry Leaves Enriched with a Concentrated Probiotic in Two Breeds (Kahuri/T and AO/T) of Bombyx mori L. Silkworm

This study aimed to assess the effect of mulberry leaf fortification with a probiotic (Enterococcus faecium and rosemary) on larval development, feed utilization efficiency, digestive performance, and cocoon-related traits in two Bombyx mori breeds. The results showed that a probiotic addition to the silkworms’ diet, particularly at a 2% inclusion level, enhances key productive traits such as larval weight, silk gland weight, cocoon weight, digestibility, and feed efficiency, while reducing excreta. Breed-specific differences were evident, with Kahuri/T exhibiting superior nutrient intake, assimilation, and overall productivity compared to AO/T (p < 0.0001). Productive traits during the 5th instar increased significantly over time, with both larval growth and silk gland development following rapid, exponential patterns. The Kahuri/T breed and the probiotic-supplemented groups—particularly at a 2% concentration—showed the most notable improvements compared with the AO/T breed and the control diet. Pearson correlation analyses identified strong positive relationships between feed efficiency, protein intake, and silk yield, underscoring probiotics as a viable strategy for sustainable productivity gains in sericulture. In conclusion, mulberry leaf fortification with Enterococcus faecium and rosemary, especially at a 2% inclusion level, significantly improved performance and nutrient utilization, with the strongest responses observed in the Kahuri/T breed. These findings highlight probiotic supplementation as an effective and sustainable strategy for enhancing sericulture.