Abstract

In breeding sheep high fertility rate is an important consideration factor. The association of genetic, nutritional and environmental conditions directly affects the fertility of ewes. There are high fertility sheep breeds (Texel, Suffolk) and other standard fertility breeds as (Romney, Criolla Araucana). Animal reproduction is modulated by sex hormones that act by binding to specific receptors. In sheep, alpha (ER-a) estrogen receptor is widely distributed in the reproductive system, modulating several mechanisms associated with reproductive system function. One factor possibly related to the difference in fertility between sheep breeds, is the differential expression level of these receptors in the reproductive system. In the present study a quantitative comparison of the immunohistochemical expression of ER-a was carried out in prepubertal sheep endometrium in high fertility (Texel) breed versus standard fertility (Araucana) breed, by measuring the integrated optical density in specific areas of the endometrium. Results indicate a significant difference between ER-a expression in endometrium off Texel breed ewes and Araucana breed ewes, and registered higher levels in all areas of evaluated Texel breed prepubertal ewes. This differential expression suggests a possible link between ER-a expression intensity and fertility in the breeds studied in this work.