Management Factors Affecting Fertility in Sheep

An Arab horse breeder in the early 13th century carried out the first insemination reported, by trapping stallion semen in wool placed in the vagina of a mare and transferring this to the vagina of another mare (Heape, 1898). Later, in 1780, an Italian priest and physiologist named Lazzaro Spallanzani performed artificial insemination with dog semen, and revolutionised the way scientists thought. Since then, scientist and farmers have striven to improve this technology, motivated by the benefits that could be achieved. Sheep is one of the species subsequently linked to this technology and in which many questions still remain to be resolved to improve fertility. However, the potential impact of this technique on the genetic progress of sheep is high and further studies are needed to improve its efficiency. In Spain, artificial insemination programmes in sheep are linked to the genetic selection schemes of the breeds, but it has not been successfully integrated with reproductive technology on farms as happen in sows or cows. The technical difficulty and weak fertility, ranged between 15 to 60 % for pregnancy rate, limits its application. In Spain, most commercial programmes use refrigerated semen (15 degrees C) by superficial intracervical deposition (cervical), whereas the use of frozen-thawed semen by intrauterine deposition (laparoscopy) is more restricted. Cervical insemination with fresh semen is the main method chosen due to its simplicity and satisfactory results. With the aim of improving its efficiency, this paper focuses on identifying the main management effects affecting AI results when this technology is applied.