Effect of Synchronization Protocols on Follicular Development and Estradiol and Progesterone Concentrations of Dairy Heifers

Abstract

The objectives were to evaluate the effect of synchronization protocols on follicular development and estradiol 17-beta (E(2)) and progesterone (P(4)) concentrations in dairy heifers. In experiment 1, 36 heifers were assigned to 1 of 6 synchronization protocols in a 3 x 2 factorial design: presynchronization with GnRH on study d -6 or -9 [study d 0 = initiation of the Cosynch + CIDR (controlled internal drug releasing insert containing P(4)) protocol] or no presynchronization (control) and one injection of PGF(2 alpha) or not on study d 0. In experiment 2, 126 heifers were assigned to 1 of 4 synchronization protocols in a 2 x 2 factorial arrangement: presynchronization or not with GnRH on study d -6 and injection of PGF(2 alpha) or not on study d 0. In experiments 1 and 2, all heifers received a modified Cosynch protocol with CIDR for 7 d starting on study d 0. After the PGF(2 alpha) of the Cosynch and removal of the CIDR, heifers were detected in estrus and inseminated. Those not inseminated by study d 10 received an injection of GnRH and were timed-inseminated. Ovaries were scanned by ultrasound on d 0, 2, and 5, daily from d 7 to 14, and on d 16. Blood samples collected on d 0, 2, 7, 9, and 16 were analyzed for P(4), and the blood sample collected on d 9 was analyzed for E(2). Pregnancy was diagnosed at 28 and 40 +/- 3 d after artificial insemination. In experiment 1, there was a tendency for the presynchronization protocol to affect the proportion of heifers ovulating in response to the first GnRH injection of the Cosynch + CIDR protocol. In experiment 2, a greater proportion of presynchronized heifers ovulated in response to the first GnRH injection. Although heifers receiving PGF(2 alpha) had larger ovulatory follicles on d 7 and before ovulation and shorter intervals to estrus and ovulation, these heifers tended to have decreased concentrations of E(2) during proestrus. Presynchronization of dairy heifers with GnRH increased ovulation in response to the first GnRH injection, and treatment of heifers with PGF(2 alpha) at initiation of the Cosynch + CIDR protocol increased the size of the ovulatory follicle and reduced the intervals to estrus and ovulation.

Endocrine and metabolic differences between Bos taurus and Bos indicus cows andimplications for reproductive management

“…In B. taurus beef cattle, Stevenson and Lamb (2016) reported little effect of P4 environment during development of the preovulatory follicle on pregnancy risk. Moreover, Holstein heifers that received PGF2α at the initiation of a Cosynch + CIDR protocol, and therefore, had lower circulating P4 during the protocol, resulting in larger ovulatory follicles, had similar P/AI as heifers not receiving PGF2α at the initiation of the protocol (Stevenson et al, 2008). In contrast, studies in B. indicus heifers or nonlactating cows indicated that high circulating P4 concentrations during synchronization of ovulation protocols reduced the growth of the dominant follicle, which negatively affected ovulation rate and pregnancy success (Carvalho et al, 2008;Dias et al, 2009;Peres et al, 2009).…”

Ovarian Response of Dairy Cows to Progesterone Combined On

“…Injection of PGF2α causes luteolysis of CL present and allows the cows to express estrus because of the reduced progesterone concentration (Stevenson et al, 2008). CONCLUSIONS It can be concluded that ovarian response after involving CIDR in the protocol for estrus synchronization especially using combination of GnRH and PGF2α were much effective to synchronize the initiation of estrus in dairy cows.…”

“…This technique has widely been used as an important tool for increasing AI submission rate in beef and dairy herds (Macmillan and Peterson 1993;Xu and Burton 1999;Lucy et al, 2001). Otherwise, efficient and accurate detection of estrus are fundamental for successful reproductive management when no fixed-time AI protocols are implemented (Heersche and Nebel, 1994;Stevenson et al, 2008). This reproductive protocol, however, requires daily observation for signs of estrus and may result in extended interval from puberty to pregnancy depending on estrus detection efficiency and accuracy (Stevenson et al, 2008).…”

“…Otherwise, efficient and accurate detection of estrus are fundamental for successful reproductive management when no fixed-time AI protocols are implemented (Heersche and Nebel, 1994;Stevenson et al, 2008). This reproductive protocol, however, requires daily observation for signs of estrus and may result in extended interval from puberty to pregnancy depending on estrus detection efficiency and accuracy (Stevenson et al, 2008). This implies that since the dairy or beef cattle producers have a difficulty to detect estrus in a certain time especially in tie-stall housing system, estrus synchronization is an alternative way for successful reproductive management.…”

Clinical Use of Progesterone and Its Relation to Oxidative Stress in Ruminants

“…Progesterone devices are removed during PGF2α injection (day 7). Fixed-time artificial insemination is performed in 48, 56, or 60 hours after GnRH is injected [38][39][40]. Such protocols may be applied for 12-14 days with progesterone [41,42].…”