Effect of direct-fed microbial feed blocks on blood β-hydroxybutyrate and milk yield in early postpartum buffaloes under field conditions

Background and Aim: Early postpartum buffaloes are highly susceptible to negative energy balance and hyperketonemia, which adversely affect metabolic health, milk yield, and farm profitability under smallholder field conditions. Direct-fed microbials (DFMs) have emerged as a promising nutritional strategy to improve rumen function and productivity; however, evidence in buffaloes under real-farm settings remains limited. This study evaluated the effect of DFM feed blocks on blood β-hydroxybutyrate (BHB) concentrations and milk yield in early postpartum buffaloes managed at farmers’ doorsteps. Materials and Methods: A field-based randomized controlled trial was conducted between February and December 2023 in three dairy herds in Gandhinagar district, Gujarat, India. Initially, 36 early postpartum buffaloes were enrolled; due to attrition, 22 animals (11 per group) were included in the final analysis. Buffaloes were randomly allocated to a DFM group or a placebo group. The DFM group received feed blocks containing a consortium of probiotic strains cultivated on agricultural by-products, while the placebo group received wheat straw blocks, both alongside a nutritionally balanced basal diet. The intervention lasted five weeks. Blood BHB concentrations were measured weekly on days 0, 7, 14, 21, and 28 using a validated handheld meter, and daily milk yield was recorded throughout the study. Data were analyzed using linear mixed models with repeated-measures. Results: DFM supplementation significantly reduced mean blood BHB concentrations compared with the placebo (1.04 ± 0.04 vs. 1.40 ± 0.03 mmol/L; p < 0.05), indicating improved metabolic status. A significant treatment × time interaction demonstrated a progressive decline in BHB levels from day 7 onward in the DFM group. Buffaloes receiving DFM produced significantly more milk than controls (9.27 ± 2.91 vs. 7.35 ± 0.31 L/day), corresponding to an average increase of 1.73 ± 0.42 L/day (p < 0.001), with consistent effects across the experimental period. Conclusion: Under practical field conditions, DFM feed blocks effectively improved metabolic health by lowering blood BHB concentrations and significantly enhanced milk production in early postpartum buffaloes. These findings support the use of DFMs as a sustainable nutritional intervention for improving productivity and metabolic resilience in buffalo-based dairy systems, while highlighting the need for further mechanistic and long-term studies.