OVARIAN FOLLICULAR DYNAMICS AND EFFECT OF BREED ON CONCEPTION RATE TO ARTIFICIAL INSEMINATION WITH FROZEN SEMEN IN MARES
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2018-06
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Abstract
Equine reproduction is unique by having long behavioral estrus and variations in ovarial follicular dynamics. Additionally, differences in time of breeding between breeds and individuals of mares made difficulty to standardize breeding time. There were a limitted data on equine reproduction and breeding in Ethiopia. An experimental study was conducted at Balderas sport horses and recreational center, Addis Ababa, Ethiopia from January to June, 2018 to determine ovarian follicular dynamics and evaluate conception rate to frozen semen in local and exotic cross breed mares. A daily transrectal ultrasonography was carried out to evaluate uterine changes and ovarian structures for 2-3 consecutive estrus cycles. Inseminations were done post ovulation within an average of 6-9h using frozen thawed semen. The mean (+SEM) of cross sectional uterine diameter were 44.4+0.5mm and 45+0.5mm for local and cross breed mares respectively; whereas endometrial fold development indicated 3.1+0.1 in local and 2.8+0.1 scores in cross breed mares with significant difference at P<0.05. The mean (+SEM) of preovulatory follicle diameter in local and cross breed mares indicated 49.1+1.0mm and 50.1+0.8mm respectively. Fast growth of dominant follicles in cross breed shorten interovulatory interval than local breed mares with length of estrus, 7.0+0.9 days for local and 6.1+0.6 days for cross breed mares. A positive correlation of teasing scores, uterine diameter and endometrial fold scores with diameter of developing dominant follicles in the present study has been used to estimate time of eminent ovulation. The overall conception rate to frozen semen was 15/21 (71.43%) with 8/11 (72.73%) in cross breed and 7/10 (70%) local breed mares. Conception rate increased significantly with increased number of services/conception with an overall mean +(SEM) of 2.2+0.2 services/conception. More number of services/conception were required for local breed (2.7+0.2) than cross breed mares (1.8+0.3) and again for lower body condition scores than higher condition scores of mares. In conclusion, measuring a cross sectional uterine diameter, endometrial folding scores and teasing scores with developing dominant follicles and their correlation were good parameters to determine relative time of ovulation and breeding in mares; whereas good management of mares for improved body conditions could require to decrease number of services per conception.
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A Thesis submitted to the College of Veterinary Medicine and Agriculture of Addis Ababa University in partial fulfillment of the requirements for the degree of Master of Veterinary Science in Veterinary Obstetrics and Gynecology
Keywords
Breeds, conception rate, follicular dynamics