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.