RESUMO
A total of 300 laying Japanese quails (230.10 ± 20 g body weight) divided into four groups (15 birds in 5 replicates/group) were used to examine the impacts of dietary sodium humate (SH) supplementation at levels of 0% (control diet), 0.2%, 0.4% and 0.6% on egg variables and physiological merits of laying quails for 10 weeks under heat stress conditions (15 June and 23 August 2021). Results showed 0.4% SH increased (p < 0.05) weight (12.27 vs. 11.91 g), production (79.84% vs. 69.20%), mass (597.13 vs. 510.48 g) and brokenness (2.8% vs. 5.4%) of eggs as compared to control. Egg shape, shell thickness, shell strength and cholesterol content as well as feed conversion ratio were higher (80.2, 295.8 µm, 1.468 kg/cm,2 11.08 mg/g and 2.69, p < 0.05) in 0.4% SH than in control group (75.2, 279.0 µm, 1.304 kg/cm,2 14.94 mg/g and 2.76). Feed intake, percentages of eggs' shells, yolk, albumen and serum biochemistry (total protein, albumin, AST and HDL) were not altered with the dietary SH. Birds fed on SH diets showed higher levels of globulin, calcium and phosphorus, as well as lower contents of albumin/globulin ratio, triglycerides, cholesterol, corticosterone compared with the control. Regression analysis of antioxidants expected higher total antioxidant capacity (TAC), superoxide dismutase, glutathione peroxidase at 0.35%, and glutathione at 0.40% SH, while the lowest concentration of malondialdehyde was computed at 0.45%. Similarly, immunoglobulins (IgG and IgM) maximum values were determined at 0.35% and 0.40% levels. Moreover, the concentration of tumour necrosis factor-alpha increased (p < 0.05) in all SH levels as compared to the control group. It is conceivable to conclude that the dietary implementation of SH at a level of 0.4% improved egg variables and well-being aspects of laying quail exposed to heat stress conditions.