Seasonal investigation of the macroscopic and microscopic structure of the sinus interdigitalis in Hamdani crossbred sheep (Ovis aries)

Background The odours of different body parts and structures, such as external genitalia, female urine, ventral tail radix, infraorbital sinus and interdigital sinus, have a strong attractiveness for rams. The sinus interdigitalis is considered an important trail gland for sexual behaviour, as its odour is included in the list of strongly attractive structures for male animals during the breeding season, being important in pheromone production. Objectives In the present study, the effects of sex and breeding season on the morphological and histological structure of the interdigital gland were investigated in Hamdani crossbred sheep (Ovis aries). Methods Sinus interdigitalis glands located on the forelimbs and hind limbs were collected from 10 male and 10 female sheep during both breeding and non‐breeding seasons. The gland's position in the forelimbs and hind limbs was determined radiographically. The glands were examined macroscopically, histologically and immunohistochemically in both seasons. Results In all animals, the topographic location of the gland between the digits was determined to be distal to the phalanx proximalis and at the level of the phalanx media. The mean weight of the gland in male and female animals was 1.07 ± 0.03 and 1.4 ± 0.11 g, respectively. In general, the results of morphometric measurements were higher during the breeding season, and the increase was more pronounced in female animals. In histological examinations, it was determined that both neck and body parts of the tissues consisted of a structure consisting of a connective tissue capsule at the outermost, dermis, epidermis and lumen underneath. Immunohistochemically staining revealed that oestrogen receptors showed positive immunoreactions only in the intracytoplasmic localization of apocrine sweat glands. In terms of morphological, histological and oestrogen receptors, it was thought that the gland may play a role in sexual communication. The manuscript is the first study on sinus interdigitalis in Hamdani crossbred sheep bred in Siirt province. Sinus interdigitalis were collected from male and female sheep breeding and non‐breeding periods, and the glands were compared macroscopically and microscopically. In this context, the topographic positions of the glands were determined macroscopically and this information was confirmed with radiographic images. In the continuation of the study, morphometric measurements were carried out on the glands. After the macroscopic examin