Bacillus Subtilis Inclusion in Lactating Goats’ Diet: A Dose-Response Evaluation of Feed Efficiency, Rumen Fermentation, Metabolic Health, and Milk Production of Does, And Performance of their Kids

Fifteen Zaraibi does (3-4 years old; live body weight: 32.69 ± 0.43 kg) were randomly assigned to three experimental groups fed three experimental rations supplemented with Bacillus subtilis, as a feed additive. The experimental period started 21 prepartum and continued until 180 days postpartum: R1 (Control, basal diet), R2 (Basal diet + 2 g B. subtilis/h/d), and R3 (Basal diet + 4 g B. subtilis/h/d). Dry matter intake (DMI), milk yield and composition, and live body weight were recorded across three lactation stages (Early, mid, and late). Serum metabolites and rumen fluid parameters were determined. Compared to the control (R1), B. subtilis treated groups (R2 and R3) increased DMI during lactation stages. In rumen liquor of does, pH value and protozoa counts decreased (P<0.05), while concentration of ammonia-N and total volatile fatty acids, and total bacterial counts increased (P<0.05) by R2 and R3. Average daily milk yield was higher (P<0.05) in R2 and R3 than in R1. Milk fat, protein and lactose percentages were improved (P<0.05) by B. subtilis supplementation, Liver enzymes (AST and ALT), and serum metabolites (Cholesterol, triglycerides, glucose, total protein, and albumin was not affected significantly by B. subtilis supplementation. Economic returns compared to the control were verified with using B. subtilis, as probiotic feed additive in goat’s diet.