Abstract
This study aimed to provide the performance, localization and expression of the epithelial calcium transporter channels Calbindin-D28k (Calb) and TRPV6, and of the morphology of the digestive and reproductive system of laying quail under heat stress (HS), and with methionine supplementation (MS). This study characterized the positivity (immunohistochemistry) and expression (real-time PCR) of calcium channels in the kidneys, intestine and uterus of 504 laying quails under different MS (100, 110 and 120%) and temperatures (20, 24, 28 and 32°C). The animals under HS (32°C) had lower villus height, villus:crypt ratio, and goblet cell index in the duodenum and jejunum, fewer secondary and tertiary uterine folds, smaller hepatic steatosis, and increased number of distal convoluted renal tubules (CT) positive to Calb, and increased positivity in proximal CTs. Deleterious effects of HS were minimized with MS for: duodenal crypts, number of goblet cells of the jejunum, number of uterine folds, decreased Calb positivity in intestines and kidney, increased positivity of Calb in the uterus and increased TRPV6 gene expression in the kidney (P≤0.05). Epithelial calcium transporters were altered due to less need for calcium absorption and reabsorption due to more calcium available with the MS, increasing egg production in HS and quality in termoneutrality (P≤0.05). MS further increased intestinal villus absorption area and height, increased steatosis, decreased Calb positivity in the intestine and kidney, increased uterine positivity of Calb, and increase Calb and TRPV6 expression in the kidney (P≤0.001) under thermoneutrality. It was concluded that the use of MS (120%) is justifiable in order to partially reverse the deleterious effects of HS on the production, in the epithelial calcium carriers, and in the digestory and reproductive morphology of laying quail.
Highlights
Quail laying farming has been growing in Brazil, mainly in the northeast region
From the histomorphometric analysis of the intestine, it was found that the villus height variable (AV) in laying quail is reduced during heat stress in the duodenum and jejunum (Table 3), corroborating Mitchell and Carlisle [24], who observed decrease in jejunal villus height of broilers kept under constant thermal stress compared to birds in thermoneutrality
Methionine supplementation is ineffective at reversing the harmful effects of heat stress for villus height (VH)
Summary
The raising of quails is a very profitable activity and with broad perspectives, which induces the development of research aiming at better production, perfecting techniques and alternatives to reach quality standards and expansion throughout the territory. In tropical climates, such as those found in most of Brazil, laying birds suffer a reduction in their zootechnical indexes as well as an increase in mortality as a result of thermal stress by heat, leading to productive and economic losses in production [1]. Nascimento et al [8] stated that 70% of the production cost is based on food, and for this reason there is a need to develop balanced diets according to the needs of the birds, enabling them to use the diet with maximum efficiency
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