Ruminal tannase-producing bacteria and their effects on growth performance, nutrient digestibility, blood parameters, and rumen bacterial populations in weaning Afshar-Kurdi lambs fed pomegranate peel

Abstract

This study investigated the effects of ruminal tannase-producing bacteria (TPB) on growth performance, nutrient digestibility, blood parameters, and rumen bacterial populations in weaning Afshar–Kurdi lambs fed pomegranate peel (PP). Forty-nine strains representing the genera Klebsiella, Escherichia, Raoultella, Enterobacter, and Pectobacterium, used to formulate an oral feed additive (OFA). The OFA was administered to thirty-six lambs aged 1–70 days, which were randomly assigned to four treatments: T1 (basal diet), T2 (basal diet + 1 mL OFA), T3 (basal diet + 5% PP), and T4 (basal diet + 1 mL OFA + 5% PP). Growth performance was not affected by dietary treatments, as dry matter intake (DMI), body weight (BW), and average daily gain (ADG) remained unchanged (P > 0.05). However, birth weight significantly influenced DMI, BW, and ADG (P < 0.05). OFA reduced ruminal pH (P < 0.0001) and improved digestibility of fiber fractions, particularly ADF and cellulose (P < 0.01). In contrast, PP increased ruminal pH and NH₃–N concentration (P = 0.009) and decreased DM and CP digestibility (P < 0.05). Significant OFA × PP interactions were observed for DM, CP, CF, NDF, and ADF digestibility (P ≤ 0.01), indicating interactive effects on fiber utilization. Blood metabolites were largely unaffected; however, OFA reduced serum uric acid (UA) by 60.5% (0.58 vs. 1.47 mg/dL; P = 0.01) and increased albumin (ALB) and Glutamate oxaloacetate transaminase (GOT, P < 0.05, while creatinine (CRE) remained unchanged. DGGE analysis revealed treatment-dependent shifts in ruminal bacterial communities, with OFA-supplemented groups showing greater band richness (≈ 11–14 bands per lane) than control and PP-only groups (< 7 bands). Overall, OFA, particularly when combined with PP, enhanced ruminal microbial diversity and fiber digestion without affecting growth performance.