Effects of Water-Delivered Probiotics on Performance, Carcass Traits, Immunity, Blood Biochemistry, and Ileal Morphology of Broilers Reared at High Stocking Density Under Warm Ambient Temperature

This study investigated the effects of dietary probiotic supplementation and stocking density on the growth performance, carcass traits, immunity, blood biochemical parameters, and ileal histomorphology of broiler chickens. A total of five hundred ten 1-day-old unsexed broiler chicks (Cobb 39) were allocated to three probiotic levels (0%, 0.1%, 0.2%) and two stocking densities (low vs. high). Results indicated that stocking density significantly influenced body weight from the third week onward, with birds reared under low density showing higher weight and better feed-to-gain ratio. Probiotic supplementation did not significantly affect weekly body weight, feed intake, or mortality, although mortality tended to be lower in probiotic-fed groups. Carcass traits and lymphoid organ indices were largely unaffected by treatments, except for a higher heart percentage in low-density birds. Cell-mediated immunity was enhanced under low stocking density, and probiotic supplementation at 0.2% increased the immune response at 48 h post-challenge. Blood biochemical analysis revealed significant effects of stocking density on total protein, globulin, and triglycerides, while probiotics reduced total lipid and LDL levels. Ileal histomorphology was significantly improved by probiotics, with increased villus height, crypt depth, and villus-to-crypt ratio. Similarly, low stocking density further enhanced these parameters. Overall, probiotic supplementation, particularly at 0.1%, combined with low stocking density, positively influenced gut morphology and immune responses, contributing to improved broiler health and performance.