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Pattern of Ovarian Follicular Development and Steroid Hormone Concentrations during Estrous Cycle of Lohi Sheep

Pattern of Ovarian Follicular Development and Steroid Hormone Concentrations during Estrous Cycle of Lohi Sheep

Muhammad Younis1, Muhammad Irfan-ur-Rehman Khan1*, Mustansar Abbas1Ali Murtaza1, Imran Mohsin2, Muhammad Shahzad3 and Muhammad Zahid Tahir1

1Department of Theriogenology, University of Veterinary and Animal Sciences, Lahore-54000
2Department of Livestock Production, University of Veterinary and Animal Sciences, Lahore-54000 
3Nuclear Institute for Agriculture and Biology, Jhang Road, Faisalabad-38000

*      Corresponding author: irfan.khan@uvas.edu.pk

ABSTRACT

The objective of the study was to determine ovarian follicular development and steroid hormones concentrations during estrous cycle of Lohi sheep. Ovaries of nine Lohi ewes were monitored for two consecutive estrous cycles using B-mode trans-rectal ultrasonography during the breeding season (Sep-Nov 2018). Plasma progesterone and estradiol-17β concentrations were determined throughout the cycle using radioimmunoassay. The average length of the estrous cycle in Lohi sheep was 17.0±0.1 days and follicular and luteal phases were 4.6±0.2 and 11.3±0.2 days long, respectively. Estrous cycles had either three or four follicular waves; 3-wave cycles were more frequent than 4-waves (87vs.13%; p≤0.05, respectively). In 3-wave cycles (n=14), follicles (≤ 3mm) emerged on Days 0.7, 5.2 and 10.5. In 4-wave cycles (n=2), follicles emerged on Days 0.1, 4, 8.5, and 11.5. The maximum diameter of preovulatory follicle and corpus luteum was 5.4±0.3 and 10.4±0.3mm, respectively. Regardless of the wave pattern, single ovulation occurred in each cycle. CL was first detectable on Day 4.0±0.1, it reached maximum diameter on Day 9.0±0.1 and luteolysis began on Day 12.2±0.2 of the cycle. Peak estradiol-17β concentration was observed 48h before ovulation and correlated with the diameter of the preovulatory follicle (r=0.84; p<0.05). Plasma progesterone concentration was maximum on Day 9±0.1 and coincided with the diameter of CL throughout the cycle (r=0.93; p<0.05). In conclusion, most of the cycles in Lohi sheep have 3-waves and are mono-ovulatory in nature.
 

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Pakistan Journal of Zoology

June

Vol. 53, Iss. 3, Pages 801-1200

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