Broodiness in birds is physically characterized by defeathering, vascularization and edema. The purpose of these morphological alterations is to facilitate the transfer of internal heat to the eggs during incubation. To the same end, arteriovenous anastomoses (AVAs) byepass the capillary blood flow from arterioles to venules in the brood patch. Unlike capillaries, which facilitate nutritional exchange between tissues and blood, AVAs function for thermo-regulatory purposes. Increased blood flow through AVAs facilitates the heat transfer from the brood patch to the embryo, a response known as Cold Induced Vasodilation. The mechanism behind CIVD is not properly characterized. A hypothetical mechanism links TRP channels with CIVD. TRP channels could allow the entry of calcium ions in the endothelial linings of AVAs for them to open. Calcium ions help in the production of endothelial nitric oxide synthase (e-NOS) enzyme which releases vasodilator substances mainly Nitric Oxide (NO) and dilates the blood vessels, resulting in the increased blood flow. It is not clear whether this response is locally or neutrally mediated.

The aim was to study whether NO exerts a higher vasodilatory role over the AVAs during the broody period to identify whether TRP channels gets up regulated more by the cold stimulus. The hypothesis is that if the vasodilatory effect of NO is higher in the broody bird than the non-broody ones, activation of TRP channels would be higher in the broody period and we can conclude that the heat transfer to the eggs is carried out by the TRP channels. Three different imaging techniques: Laser Doppler Flowmetry; Tissue Viability Imaging and Mediscope have been used to standardize a technique to study the skin microcirculation in birds since there is no recommended method to study the same.