Dose-Related Associations of a Palm Kernel Meal-Derived Mannan-Oligosaccharide-Containing Hydrolysate with Selected Immune and Ruminal Fermentation Measures in Growing Goats

Mannan-oligosaccharides (MOS) may influence microbial and immune-related processes, but evidence concerning palm kernel meal (PKM)-derived MOS-containing products in goats remains limited. The experimental product was a chemically heterogeneous PKM-derived hydrolysate in which M2–M6 oligosaccharides were identified by HPLC–RID; residual sugars and other soluble constituents were also present. Twenty growing male goats received 0, 2.5, 5.0, or 10.0 g hydrolysate/goat/day (n = 5 per treatment) for 90 days. Feed intake, growth, hematological and serum biochemical indices, circulating immune indicators, peripheral blood leukocyte gene expression, and selected ruminal measures were evaluated. Immune and gene-expression outcomes were measured in prefeeding blood collected on Day 90. Ruminal pH and acetate, propionate, and butyrate were measured in a single rumen-fluid sample collected 3 h after feeding on Day 90. Serum IgA showed a positive linear association with supplementation level, whereas IL-1β and IL-6 showed negative associations; these remained significant after false-discovery-rate correction (q = 0.036, 0.012, and 0.012, respectively). Selected immune-related transcripts also differed among treatments, but these endpoint patterns do not establish coordinated immunological regulation or a specific mechanism. Propionate and butyrate showed nominal positive linear associations, whereas the acetate-to-propionate ratio showed a nominal negative association (raw p = 0.028, 0.021, and 0.018, respectively); none remained significant after correction (q = 0.056 for each). Ruminal pH, the sum of the three measured VFA concentrations, feed intake, and growth did not differ detectably. No overt clinical abnormalities requiring veterinary intervention were observed, but the study was not powered to establish safety. These preliminary between-group endpoint associations concern the complete heterogeneous hydrolysate and cannot be attributed specifically to M2–M6 oligosaccharides. Larger, adequately powered studies with pretreatment and repeated measurements are required.