Variation Factors of the Pregnancy Rate of Arab Pure Breed Mares Inseminated by the Deep Intracornual Method in Post-ovulation

This work was aimed to study the influence of different factors on the pregnancy rate in the Pure Arab Breed (PAB) mares, inseminated intra-cornually in post-ovulation. A total of 62 thoroughbred PAB mares were inseminated by this method during the breeding season of 2016. Almost half of these mares (28) received an hCG- treatment (Chorulon®) to induce ovulation. Heat in all the mares was detected by rail teasing, and their follicular activity monitored 3 times a day by ultrasound (9am, 4pm and 11pm) until observation of the corpus luteum. At this moment, intracornual artificial insemination with frozen semen (AIF) is executed and the pregnancy rate is determined after the pregnancy confirmation examination, at 35 days post AI. Results showed that the pregnancy rate does not vary between the group of mares treated with Chorulon® (37%) and that of untreated mares (34%). However, this parameter varies significantly according to the moment op AI (21.5% if the AI occurs at 4pm versus 36% and 36.5% respectively if the AI is practiced immediately after the 9am and 11pm ultrasound examinations, respectively, p<0.05). Moreover, the rate of pregnant mares is higher when the ovulation occurs in the right ovary (p<0.05). A significantly higher number of pregnancies is obtained when the diameter of the preovulatory follicle measures between 35 to 44 mm (p<0.05). The identified variation factors influencing the pregnancy rate in PAB mares are the moment of insemination, the ovary where the ovulation occurs, and the diameter of the preovulatory follicle.