In tropical and subtropical climate regions, heat stress is one of the main causes of production losses in laying quails, aggravated by the antinutritional effects of the phytate in diet ingredients, which negatively affect the bioavailability of minerals, especially calcium and phosphorus. This situation results in a reduction in production and the quality of eggs from commercial laying quails. Several nutritional strategies are utilized to reduce the adverse effects of high temperatures and antinutritional factors such as phytate. Among these strategies, the use of exogenous enzymes, such as phytase, stands out as a viable alternative. Phytase breaks down phytate molecules, optimizing the absorption of essential minerals and improving productive performance and egg quality under unfavorable conditions. Specifically, it is recommended to use 1500 FTU of phytase, as it not only reduces the effects of thermal stress but also enhances eggshell thickness and calcium absorption. In this context, this bibliographic review sought to produce a document demonstrating the beneficial effects of the phytase enzyme on the hydrolysis of the phytate molecule, the availability of calcium for Japanese quails (Coturnix japonica), and its implications in thermal stress due to heat.

Context: Thermal stress causes significant changes in the bioavailability of minerals, especially calcium, in laying birds, resulting in reduced egg production, and compromising egg quality. Therefore, it is necessary to use additives that provide better nutrient availability and minimise the negative effects caused by high temperatures. Aims: This study aimed to evaluate the effects of super-dosing the diet of laying quails submitted to different temperatures with phytase on their bone parameters and on the epithelial calcium transporter calbindin-D28K positivity. Methods: Seven hundred and twenty (720) Japanese quails in the production phase were distributed in a completely randomised design, in a 5 × 3 factorial design, with five supplementation levels of phytase (0, 500, 1000, 1500, and 3000 FTU/kg), and three temperatures (24°C, 30°C and 36°C), totalling 15 treatments, and six replications of eight birds each. The study began at the 8th week of age and continued for two cycles of 21 days, totalling 42 days of experiment. Bone parameters of the tibias and calbindin-D28K positivity were measured by immunohistochemistry. The data were submitted to variance, Tukey, and regression analyses. Key results: At 24°C, birds had higher averages for proximal, medial, and distal diaphyses than did birds at 30°C and 36°C, and a greater breaking strength of the tibias than did those at 36°C. There was an increasing linear effect on the medial diaphysis and Seedor index in the tibias with an increasing phytase supplementation level. Calcium (Ca) in the tibias was higher in birds kept at 30°C at a supplementation level of up to 1000 FTU of phytase, than in the birds at 24°C and 36°C, equalling at 1500 FTU, and lower at 3000 FTU. There was a quadratic effect for phosphorus (P) and the Ca:P ratio in the tibias of quails submitted to increasing concentrations of phytase. Quails kept at 30°C showed greater anti-calbindin-D28K positivity in the duodenum and jejunum, when compared to animals subjected to temperatures of 24°C and 36°C. Phytase doses of 500 and 1000 FTU increased calbindin-D28K positivity in the duodenum of quails kept at 30°C. At a supplementation level of 1500 FTU, phytase provided greater eggshell thickness and greater calbindin-D28K positivity in the uterus of quails kept at 36°C. Conclusions: Therefore, it is recommended to use 1500 FTU of phytase for Japanese quail exposed to high temperatures. Implications: These findings suggest that dietary phytase super-dosing can help alleviate thermal stress in Japanese quail.

This study aimed to evaluate the effects of phytase superdosing in the diet of Japanese quails subjected to different thermal conditions on productive performance, egg characteristics, intestinal morphometry, and physiological parameters. The experiment was conducted in a completely randomized design in a 5 × 3 factorial arrangement, consisting of five phytase levels (0, 500, 1000, 1500, and 3000 FTU/kg) and three temperatures (24, 30, and 36°C), with six replicates of eight birds each. The performance variables evaluated included feed intake, egg production, egg weight, egg mass, feed conversion per egg mass, and feed conversion per dozen eggs. Egg quality was assessed by yolk color, shell thickness, specific gravity, Haugh units, and proportions of yolk, albumen, and shell. Spleen, liver, heart, and abdominal fat weights were also measured, along with duodenum and jejunum morphometry. Data were subjected to analysis of variance, Tukey's test, and regression analysis. Birds kept at 36°C showed lower feed intake compared with those maintained at 24 and 30°C (P < 0.001), with no significant effect of phytase on performance. Supplementation with 1500 FTU increased eggshell thickness at 36°C (P < 0.001). A temperature × phytase interaction was observed for liver weight (p = 0.010), whereas heart weight was higher at 24°C compared with 36°C (P = 0.005). The effects of phytase on duodenal morphometry were temperature-dependent, with the greatest absorptive area observed with 3000 FTU at 30°C (P < 0.001). The temperature of 24°C resulted in the best morphological parameters and the lowest hepatic glycogen index. It is concluded that although quails tolerate temperatures of 36°C, the best productive responses occur at 30°C. Therefore, the use of 1000 to 1500 FTU is recommended, as these levels provided benefits to intestinal morphometry and egg quality.

In tropical and subtropical climate regions, heat stress is one of the main causes of production losses in laying quails, aggravated by the antinutritional effects of the phytate in diet ingredients, which negatively affect the bioavailability of minerals, especially calcium and phosphorus. This situation results in a reduction in production and quality of eggs from commercial laying hens. Several nutritional strategies are utilized to reduce the adverse effects of high temperatures and antinutritional factors such as phytate. Among these strategies, the use of exogenous enzymes, such as phytase, stands out as a viable alternative. Phytase breaks down phytate molecules, optimizing the absorption of essential minerals and improving productive performance and egg quality under unfavorable conditions. In this context, this bibliographic review sought to produce a document demonstrating the beneficial effects of the phytase enzyme on the hydrolysis of the phytate molecule and the availability of calcium for Japanese quails (Coturnix coturnix japonica), and its implications in thermal stress due to heat.

This study evaluated the effects of increasing phytase levels on serum biochemical parameters and renal and hepatic changes in Japanese quails (Coturnix japonica) under different temperature conditions. A total of 720 quails were distributed in a 5 × 3 factorial design with five phytase levels (0, 500, 1000, 1500, and 3000 FTU/kg) and three temperature ranges (24, 30, and 36 °C), totaling 15 treatments with six replicates of eight birds each. Data were collected in cycles 2 and 4. The parameters measured included eggshell thickness (ST), total egg production (TEP), liver weight (LW), gamma-glutamyl transferase (GGT), alanine aminotransferase (ALT), aspartate aminotransferase (AST), alkaline phosphatase (FA), phosphorus (P), calcium (Ca), urea (URE), creatine kinase (CK), and uric acid (UA). PRO was higher at 30 °C compared to 24 °C and 36 °C. EC showed a significant interaction between phytase levels and temperature, with phytase improving EC, especially at 1500 FTU and 36 °C. PF was not affected in the second cycle but had a quadratic effect in the fourth cycle. Phytase supplementation improved shell thickness and regulated biochemical parameters, especially at high temperatures. Based on these results, a phytase level of 1500 FTU/kg is recommended to optimize performance and mitigate the negative effects of high temperatures on quail health.