Natural vs synchronized estrus: determinants of successful pregnancy in ewes using frozen-thawed Suffolk semen

• Published in: Journal of animal reproduction & biotechnology (Online) Vol. 35; no. 2; pp. 183 - 189
• Main Authors: Rahman, Md. Mahbubur, Naher, Nazmun, Isam, Md. Mofijul, Hasan, Moinul, Naznin, Farhana, Bhuiyan, Mohammad Musharraf Uddin, Bari, Farida Yeasmin, Juyena, Nasrin Sultana
• Format: Journal Article
• Language: English
• Published: The Korean Society of Animal Reproduction and Biotechnology 30.06.2020; 사단법인 한국동물생명공학회
• Subjects: estrus; pregnancy rate; progesterone; vaginal electrical resistance (ver); 축산학
• ISSN: 2671-4639; 2671-4663
• DOI: 10.12750/JARB.35.2.183

The pregnancy rate in indigenous ewes inseminated with frozen-thawed Suffolk semen following natural and synchronized estrus was determined. The serum Progesterone and Estrogen concentration and vaginal electrical resistance (VER) of ewes at the time of Artificial Insemination (AI) were observed as successful pregnancy determinants. 21 healthy ewes were selected for this experiment during JanuaryApril, 2017. 10 ewes were inseminated in natural estrus. Whereas, 11 ewes were inseminated after estrus synchronization using intravaginal sponges containing 60 mg medroxyprogesterone acetate. Trans-cervical Al (TCAI) was performed in all ewes within 12-16 hours of observed heat. Prostaglandin E1 analogue impregnated vaginal sponge was used for cervical relaxation 6-8 hours before insemination. Pregnancy was diagnosed through trans-abdominal ultrasonography after 40 days of AI. The pregnancy rate of ewes in synchronized estrus was higher (54.5%) than in natural estrus (30%). Higher serum Progesterone level (0.90 ± 0.02 ng/mL) and significantly (p < 0.001) lower VER (257.78 ± 10.11 ohm) were observed at the time of AI in ewes becoming pregnant. Results suggest that higher Progesterone concentration and lower VER could be considered as pregnancy indicators. Oestrous synchronization could be implemented to increase the pregnancy rate in ewes.