Princess Nourah bint Abdulrahman University

Lactic acid bacteria (LAB)-based probiotics are widely recognized as effective and sustainable alternatives to antibiotic growth promoters due to their ability to improve intestinal integrity, modulate host immunity, and enhance productive performance in poultry. This study evaluated the effects of Pediococcus acidilactici (1 × 10 8 CFU/g) administered via drinking water on the productive performance, egg quality characteristics, hatching traits, serum biochemical indices, and immune responses of broiler breeder hens. A total of 240 hens (29 weeks old) were randomly assigned to four treatment groups receiving 0.0, 0.1, 0.2, or 0.3 g of Pediococcus acidilactici per liter of drinking water, with six replicates of ten birds each. All birds were maintained under standardized management and environmental conditions for an eight-week experimental period. Supplementation at 0.2 and 0.3 g/L significantly increased egg production, egg weight, and egg mass, while also improving feed efficiency ( P < 0.05) without affecting feed intake, final body weight, or livability ( P > 0.05). These inclusion levels also enhanced reproductive performance—including settable eggs, fertility, hatchability, and hatch of fertile eggs—while reducing embryonic mortality ( P < 0.05). In terms of egg quality, hens receiving 0.2 and 0.3 g/L exhibited significant improvements in egg length, egg width, and Haugh unit scores ( P < 0.05), whereas other internal and external egg quality parameters remained statistically unchanged ( P > 0.05). Furthermore, probiotic supplementation at these levels significantly reduced serum triglyceride concentrations and elevated antibody titers against Newcastle disease and infectious bronchitis viruses ( P < 0.05). Taken together, these findings demonstrate that supplementing drinking water with PA, particularly at a concentration of 0.2 g/L, can effectively enhance the productivity, reproductive performance, and immune status of breeder hens. Future research should explore the long-term effects of PA across different genetic strains and production stages, while also integrating gut microbiota profiling and metabolic studies to better elucidate the underlying biological mechanisms.