Characterization of Ovarian Follicular Dynamics and Estrus Behavior in Fogera and Jersey Cattle Breeds

Abstract

Ovarian follicles grow in a wave-like fashion during the estrus cycle of female animals. Understanding the reproductive physiology of female animals is used to optimize reproductive management. The current study was conducted from January to march 2022 at Ada’a Barga dairy farm to characterize the follicular dynamics and estrus behavior of Fogera and Jersey breeds. For this purpose, a total of 15 experimental animals (9 Fogera heifers and 6 Jersey cows) were used. A single intramuscular injection of 2ml PGF2α (Estrumate, Holland) hormone was used to synchronize and bring all animals to the same physiological status. For each cow, estrus behavior signs were visually observed and recorded. Follicular population, day of emergency, growth and atresia of the dominant follicle, a diameter of follicle, and ovary size during estrous cycles were evaluated using a trans-rectal real-time B-mode ultrasound system for three consecutive estrus cycles. Descriptive statistics was used to calculate the mean, variance, and standard deviation of means, and a comparison between the groups was done by t-test. Fogera heifer responded well to the hormonal synchronization. Fogara heifers (n=9) manifested two (29.62%), three (55.55%), and four (14%) follicular waves whereas Jersey cows (n=6) showed two (38.9%) and three (61.11%) follicular waves. Cycle length or inter ovulatory interval was 20.35 ± 2.8 and 20.67 ± 2.6 days for Fogera heifers and Jersey cows, respectively. The mean number of follicular population per animal was 13.9 ± 5.9 for Fogera heifers and 17.9 ± 7.0 for Jersey cows, where a statistically significant (p=0.000) difference was observed between the two breeds. The mean maximum diameter of the ovulatory follicle for Jersey cows was 17.2 ± 0.86 mm and for Fogera heifers 15.22 ± 1.3 mm. There was no statistical difference between the breed in terms of inter ovulatory interval (IOI), however, the difference is statistically significant (p=0.000) in terms of follicular population and dominant ovulatory follicle size. It was concluded that the follicular dynamics of fogera heifers and jersey cows were characterized by a higher incidence of cycles with two or three follicular waves and jersey cows proved to have better for follicular population than fogera heifers.