Abstract This study evaluated the impact of adding two levels of Bacillus subtilis (2 g and 4 g/head/day) to concentrate diet of dairy goats across 180 day (early, mid, and late of lactation), on the productivity, rumen fermentation, nutrient digestibility, some blood biochemical parameters, and economic efficiency. Fifteen goats were divided into three groups (n = 5 each). The control group (G1) was fed on the basal diet without additives, while treated groups (G2 and G3) received the basal diet with 2 g and 4 g of B. subtilis, respectively. The results showed that the addition of B. subtilis has significantly improved total intake as well as dry matter and all nutrients digestibility. All rumen parameters were significantly affected (p ≤ 0.05) by treatments. The pH values were decreased while the concentrations of ammonia-N, total FVA, and microbial protein were increased, but the protozoa count was decreased, the highest values were recorded with G3. Milk yield and milk composition (fat, protein, and lactose) were enhanced, particularly in G3, with significant improvements in reproductive traits and growth performance. The treated groups exhibited increased glucose, albumin, and HDL, alongside reduced ALT, AST, creatinine, and LDL levels, which was an indicator of improved liver and kidney function and metabolic health. Regarding economic efficiency, it was highest in G3, highlighting the viability of probiotic inclusion in practical goat farming. So it can be concluded that using B. subtilis for dairy goats as a functional feed additive enhances performance, health, and profitability in the different stages of milk production.
Gad et al. (Tue,) studied this question.