Semester of Graduation

August 2022

Degree

Master of Science (MS)

Department

Animal Sciences

Document Type

Thesis

Abstract

Over the course of two years (2021-2022), two experiments were conducted during the nonbreeding seasons to evaluate the in vitro developmental potential of oocytes derived from seasonally anovulatory mares treated with ECP-sulpiride. The objective of experiments 1 and 2 were to compare pooled recovery and maturation rates of oocytes from mares treated with estradiol cypionate (ECP) and sulpiride with oocytes collected from naturally transitional mares (controls). Cleavage rates of oocytes subjected to intracytoplasmic sperm injection (ICSI) were compared only in experiment 2. In experiments 1 and 2, a total of 36 light horse and pony-cross anovulatory mares were used. Treatment was administered intramuscularly and consisted of 50 mg ECP followed by 3 g sulpiride (n = 18) in sucrose acetate isobutyrate (SAIB), while controls received vehicle only (n = 18). Jugular blood samples were collected prior to treatment and continued daily for 12 days in order to characterize plasma LH and prolactin concentrations. All mares were subjected to ovum pick up (OPU) when the first 30 mm follicle of the season was detected. All follicles ≥ 8 mm were targeted for OPU and aspirates from three follicle diameter categories (8-19 mm, 20-29 mm, and > 30 mm) were pooled within treatment groups. In experiments 1 and 2, 7/7 and 10/11 ECP-sulpiride treated mares responded within 15 days of treatment. Mean day to first 30 mm follicle of ECP-sulpiride treated mares was advanced in experiments 1 (P = 0.005) and 2 (P = 0.0007) by 23 and 19 days, respectively. In both experiments, plasma prolactin and LH increased (P ≤ 0.0001) in all mares treated with ECP-sulpiride for at least 7-10 days after treatment. The recovery and maturation rates of oocytes from ECP-sulpiride and vehicle only treated mares did not differ (41.6 vs 45%; P = 0.77 and 55.6 vs 65.4%; P = 0.47, respectively) and there was no significant effect on follicle diameter. Cleavage rates of oocytes subjected to ICSI did not differ between ECP-sulpiride and vehicle only treated mares (71.4 vs 61.3%; P = 0.99, respectively).

Date

7-12-2022

Committee Chair

Oberhaus, Erin

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