Effects of Dietary Intervention Using Spirulina at Graded Levels on Productive Performance and Physiological Status of Quail Birds Reared under Elevated Temperatures

The current study aimed to explore the effect of Spirulina platensis (SP) inclusion at various levels in quail diets, in terms of their production performance, physiological traits, stress measurements, and immunological parameters under heat stress (HS) conditions. Four hundred Japanese quail ( Coturnix japonica ) chicks, one day old, were equally distributed into forty wire cages, and the cages were placed in two chambers with environmentally controlled systems (20 cages in each chamber). From 21 to 42 d of age, the quails were randomly subjected to a factorial design of two HS treatments × four SP treatments. To induce HS treatments in the quails, the first chamber was maintained at a thermoneutral temperature of 24 °C (TN group), while the temperature of the second chamber was elevated to 35 °C during the daytime (9:00–17:00 h), followed by a thermoneutral temperature for the remaining 24 h cycle (HS group). The birds in each chamber were further allocated into four SP treatments (5 replicate cages × 10 birds per cage in each treatment), where the quails were fed on a basal diet that included 0, 5, 10, or 15 g/kg SP (SP0, SP5, SP10, and SP15 groups, respectively). After exposure to the HS, a significant ( p < 0.05) reduction of 5% in body weight and 9% in both weight gain and feed intake was recorded, and the slaughter performance of the quails was adversely ( p < 0.05) affected. In addition, HS significantly ( p < 0.05) impaired the physiological traits (total protein, albumin, globulin, alanine transferase, aspartate transferase, creatinine, uric acid, cholesterol, and triglycerides) and immunological parameters (total white blood cells, heterophil to lymphocyte ratio, and T- and B-lymphocyte stimulation indexes), but increased the stress measurements (corticosterone, malondialdehyde, interleukin-1β, and tumor necrosis factor-α). In contrast, most of these parameters were linearly ( p < 0.05) improved by increasing the SP levels in the diets of the TN quail group. When the SP was included in the diets of the HS quail group, the deleterious effects of HS on the alanine and aspartate transferase activities, creatinine, uric acid, triglycerides, corticosterone, interleukin-1β, and tumor necrosis factor-α levels, heterophil to lymphocyte ratio, and T- and B-lymphocyte stimulation indexes were remarkably ( p < 0.05) relieved. These results concluded that SP nutritional application can improve the production performance and the overall physiological homeostasis of the Japanese quail, especially when suffering from heat stress.