Effects of methionine supplementing on intestine, liver and uterus morphology, and on positivity and expression of calbindin-D28k and TRPV6 calcium carriers in laying quails in thermoneutral conditions and under thermal stress

The aim of this study was to provide support for 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 quails under heat stress, and with methionine supplementation. Therefore, the present study characterized the positivity (immunohistochemistry) and expression (real-time PCR) of calcium channels (Calb and TRPV6) in the kidneys, intestine and uterus of 504 laying quails that were submitted to different methionine supplementation (100, 110 and 120%) and temperatures (20, 24, 28 and 32oC). The animals under thermal stress 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 (protein), and increased positivity in proximal CTs. The deleterious effects of heat stress were minimized with methionine supplementation for the following variables: 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. Calcium transporters were altered due to less need for calcium absorption and reabsorption due to more calcium available with the supplementation, increasing egg production and quality. Methionine supplementation further increased intestinal villus absorption area and height, increased steatosis, decreased Calb positivity in the intestine and kidney, increased uterine positivity and Calb expression, and increased TRPV6 expression in the uterus under thermoneutrality. This is the first study that describes the gene and protein expression of calcium transporters in the intestine, kidney and uterus of laying quails, and concludes that the use of methionine supplementation is justifiable in order to partially reverse the deleterious effects of thermal stress on the production.