Effect of dietary saffron (Crocus sativus) petal extract on growth performance, blood biochemical indices, antioxidant balance, and immune responses of broiler chickens reared under heat stress conditions

To evaluate the alleviative effects of saffron (Crocus sativus) petal extract (SPE) on growth performance, blood biochemical indices, antioxidant status, and immunity of heat-stressed broilers, 250 newly hatched male broiler chickens were randomly allocated to control diet (basal diet, two groups), or control diet supplemented with 300, 500, or 700 mg SPE/kg diet, with five replicates and 10 birds each. The broiler chickens, except one of the control groups, were exposed to heat stress (HS, 37 ± 1 °C, 55% relative humidity) for 6 h/day from day 25 to 42. Heat stress reduced body weight gain (BWG), feed intake (FI), and abdominal fat percentage, and increased feed conversion ratio (FCR, p < .05). It also caused decreases in the antibody production against sheep red blood cells (SRBC) and Newcastle disease virus (NDV) and an increase in the heterophil: lymphocyte (H: L) ratio. However, SPE linearly increased the FI during the entire experimental period (p = .024) and linearly improved the BWG and FCR during the finisher and entire experimental periods (p < .05). The abdominal fat percentage decreased linearly with increasing dietary SPE levels (p < .005). Dietary SPE also caused significant reductions in the plasma concentration of cholesterol (L, p < .001), uric acid (L, p < .001), and MDA (L, p < .001; Q, p < .001) and enzyme activity of LDH (L, p = .002; Q, p = .015) and AST (L, p = .002; Q, p = .019), whereas enhanced the total protein concentration (L, p = .006), SOD and GPx (L, p < .001; Q, p = .028) activities, and TAC content (L, p < .001). Meanwhile, supplementation with dietary SPE enhanced the bursa percentage (p = .05) and improved the primary and secondary antibody production titres against SRBC and antibody response to NDV at 24 and 24 days (p < .01). The results indicate that SPE is an effective additive for broiler chickens under heat stress conditions. According to estimates of regression models, the optimum amount of extract recommended is 689.5 mg/kg.HIGHLIGHTS Saffron petal extract (SPE) enhanced the growth performance of heat-stressed broiler chickens. Dietary SPE improved the liver function in broilers reared in heat stress conditions. Supplementation of SPE improved the antioxidant status and immune responses in heat-stressed broiler chickens.