Effects of Prenatal Ursodeoxycholic Acid and Probiotic Supplementation on Stress Parameters, Immune Response and Lamb Survival Rates in Ewes.

To evaluate the effects of prenatal ursodeoxycholic acid (UDCA) and probiotics-alone or combined-on colostrum quality and lamb survival in ewes. Forty Middle Anatolian Merino ewes were randomized to control, UDCA (5 mg/kg/day), PRO (probiotic 0.2 mL/kg; 6.2 × 107 colony-forming unit (CFU)/mL ≈ 1.24 × 107 CFU/kg) or UDCA + PRO for the last month of gestation. Maternal blood/colostrum was sampled pre- and postpartum; lamb serum was sampled at 24 h to assess immunoglobulin G (IgG), total antioxidant capacity (TAC), total oxidant status (TOS) and colostrum composition (IgG, fat, protein and lactose). Growth and survival were monitored to weaning. Maternal treatments significantly affected colostral IgG (p = 0.017; highest in UDCA + PRO). In lambs, IgG (p = 0.037), total protein (TP) (p = 0.021) and albumin (p = 0.011) differed by group, favouring UDCA + PRO. Survival improved with treatment (p = 0.0014). Across groups, time effects were observed for triglycerides (p < 0.001), cholesterol (p = 0.002), gamma-glutamyl transferase (GGT) (p < 0.001) and bilirubin (p = 0.004). Treatment-specific changes included PRO increasing colostrum fat (p = 0.010) and lactose (p = 0.050) and lowering maternal GGT (p = 0.021) while elevating TOS (p = 0.032) and TAC (p = 0.039); UDCA + PRO increased postpartum TOS (p = 0.034) and TAC (p = 0.005); UDCA altered glucose and triglycerides (both p = 0.015). In hierarchical regression, maternal IgG and colostrum IgG positively predicted neonatal IgG (p = 0.005). A higher order interaction suggested attenuation of transfer efficiency when maternal IgG, maternal TP and colostrum IgG were simultaneously high (p = 0.088). Combined UDCA + PRO most consistently enhanced passive immunity indicators and survival.