Superdosagem de fitase em dietas de codornas japonesas sob estresse térmico: implicações nos transportadores de cálcio calbindin-D28K е TRPV6

Abstract

Poultry farming in hot climate regions faces significant challenges due to thermal stress, which compromises mineral metabolism and egg shell quality, especially in commercial laying hens. In addition, antinutritional factors, such as phytate, present in the ingredients of diets, reduce the bioavailability of essential minerals like calcium and phosphorus, negatively impacting the performance of the birds. Supplementation with phytase emerges as an effective strategy to release these minerals, as the enzyme breaks down the phytate molecule, making the nutrients available for absorption by the birds. Although there are studies with laying hens and broilers that demonstrate the benefits of phytase, there are few studies using this enzyme in quails, especially under thermal stress conditions and with overdosing, which makes this research field still underexplored. The aim of this study was to evaluate the effects of phytase overdosing on productive performance, bone quality, serum biochemistry, and the gene expression of calcium transporters Calbindin-D28K and TRPV6 in Japanese quails (Coturnix japonica) under different temperatures. The experiment was conducted with 720 quails, using a completely randomized design and a 5 × 3 factorial arrangement, with five levels of phytase (0, 500, 1000, 1500, and 3000 FTU/kg) and three temperatures (24°C, 30°C, and 36°C), totaling 15 treatments, with six repetitions of eight birds each. The results showed that supplementation with phytase improved egg shell thickness and calcium absorption, mitigating the effects of thermal stress. Bone analysis indicated that the mineral density and strength of the tibias were favored by the enzyme, suggesting a positive impact on skeletal integrity. Calbindin-D28K expression in the uterus was higher at 30°C, and renal expression was influenced by the interaction between temperature and phytase levels. At 36°C, the birds exhibited poorer performance and biochemical alterations typical of thermal stress. Based on the results, phytase supplementation, especially at 1500 FTU/kg, was effective in mitigating the effects of thermal stress, promoting better calcium absorption, egg shell quality, and bone health in laying quails. The study also highlighted the importance of gene regulation of calcium transporters in response to thermal stress. In a scenario of climate change, optimized phytase supplementation could be a promising tool to improve bird performance under adverse conditions. Future studies are needed to further understand the molecular mechanisms involved in the modulation of mineral absorption and to assess the feasibility of phytase supplementation in different production phases and quail strains.