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Ovarian follicular dynamics, LH profiles, corpus luteum function and pregnancy following two ovulation synchronization/timed artificial insemination protocols in cattle Aali, Muhammad

Abstract

The reduced fertility following earlier estrus synchronization protocols made it necessary to develop new protocols based on our understanding of ovarian follicular dynamics and corpus luteum (CL) function in cattle. "Ovsynch" and "CIDR" are emerging protocols for ovulation synchronization that would facilitate artificial insemination at a fixed time (TAI) without estrus detection. Unfortunately, the limited and available literature on Ovsynch and CIDR treatment protocols focuses mainly on ovarian follicular dynamics during treatment and ovulation synchronization success. Therefore, the objectives of this study were to compare L H profiles, follicular dynamics, CL function and pregnancy rates (PR), following treatment with Ovsynch and CIDR ovulation synchronization/TAI protocols. In the first experiment, ultrasonography was performed throughout the treatment protocols and following ovulation for one complete cycle to monitor ovarian follicular and CL dynamics. Serial blood samples were taken to determine the L H profile and progesterone (P₄) concentrations throughout the treatment protocols and for one complete cycle following ovulation. Prolonged duration and larger diameter of the ovulatory follicle in the Ovsynch compared to CIDR protocol did not affect post synchronization LH profiles, follicular dynamics and P₄ concentrations, which were similar between Ovsynch and CIDR ovulation synchronization protocols. In experiment 2, CL's formed after Ovsynch and CIDR ovulation synchronization protocols were incubated with four different hormone treatments; LH, PGF[sub 2α] LH + PGF[sub 2α], and control (no treatment) to determine in vitro P₄ secretion. Corpora lutea formed after Ovsynch and CIDR ovulation synchronization protocols yielded similar in vitro P₄ concentrations at different stages of the synchronized cycle. The response to LH, PGF[sub 2α], and LH + PGF[sub 2α] was also not different between the two ovulation synchronization protocols. In experiment 3, the focus was to compare in vivo P₄ profiles and PR in lactating dairy cows following treatment with the Ovsynch and CLDR ovulation synchronization/TAI protocols. In vivo P₄ production and PR were similar between the Ovsynch and CIDR treatment protocols. Similar post synchronization LH profiles, follicular dynamics, P₄ profiles and PR following Ovsynch and CIDR ovulation synchronization protocols suggest that both protocols can be equally effective in synchronization of ovulation, elimination of estrus detection and enhancement of pregnancy in heifers as well as in cows. However, based on frequency of handling, cost, and industry approval, this study favors the use of the Ovsynch over the CIDR for ovulation synchronization in cows and heifers.

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