Effects of estradiol cypionate (ECP) on ovarian follicular dynamics, synchrony of ovulation, and fertility in CIDR-based, fixed-time AI programs in beef heifers
Introduction
Estradiol-17β (E-17β) and estradiol benzoate (EB) are commonly used to synchronize follicular wave emergence [1], [2], [3], [4] and ovulation [5], [6], [7], [8] in controlled internal drug release (CIDR)-treated cattle. However, estradiol cypionate (ECP), an ester of estradiol with a low water solubility that delays its release from the site of injection, is the only estrogen ester licensed for use in cattle in North America. Plasma concentrations of estradiol were prolonged (98–170 h) after intramuscular administration of large doses (5–10 mg) of ECP [9], [10]. However, when ovariectomized beef heifers were treated with only 2 mg ECP, the duration of estrus (15.8±1.1 h) was not different from heifers with a spontaneous estrus [11], suggesting that reduced doses of ECP may be useful in estrus synchronization regimens.
The effects of ECP on ovarian follicular wave emergence and ovulation have been studied in lactating Holstein cows [12]. Although 1 mg ECP was more efficacious than 0.5 mg in synchronizing follicular wave emergence, the authors concluded that the prolonged half-life of ECP made it far less efficacious than E-17β for synchronizing both follicular wave emergence and ovulation in CIDR-treated dairy cattle. However, Lopes et al. [13] used ECP successfully to replace the second treatment with GnRH to synchronize ovulation for fixed-time AI (FTAI) in an Ovsynch-type program in dairy cattle. Furthermore, Ambrose et al. [14] reported that 0.5 mg ECP administered concurrently with CIDR removal synchronized ovulation in Holstein heifers that had received PGF 24 h before CIDR removal. To our knowledge, the use of ECP in comparison or combination with E-17β or EB for FTAI in beef cattle has not been reported.
Four experiments were designed to study and compare the effects of ECP (with or without injectable progesterone), E-17β, and EB on follicular dynamics, time of ovulation, and pregnancy rate to FTAI in CIDR-based protocols. In addition, the duration of CIDR treatment (8 days versus 9 days) on the interval from CIDR removal to ovulation was determined.
Section snippets
Experiment 1
Puberal, crossbred beef heifers 18–20 months of age (n=24), received a once used intravaginal progesterone releasing device (CIDR; Bioniche Animal Health; Belleville, Ont., Canada) at random stages of the estrous cycle, and were randomly assigned to two groups to concurrently receive either 1 mg estradiol cypionate i.m. (ECP; Pharmacia Animal Health, Orangeville, Ont., Canada; n=13) or 1 mg ECP plus 50 mg commercial progesterone preparation (CP; Progesterone 5%®, J Webster Lab Inc., Victoriaville,
Experiment 1
Two heifers, one in each treatment group, did not respond to treatment to induce follicular wave emergence at CIDR insertion and they were excluded from the calculation of the interval from treatment to wave emergence. There was an effect of day (P<0.0001) on diameter of the regressing follicle, but the effects of treatment (P=0.17), and the treatment by day interaction (P=0.66) were not significant. Similarly, the effects of day (P=0.35), treatment (P=0.99) and the treatment by day interaction
Discussion
Although the administration of 1 mg ECP resulted in relatively synchronous follicular wave emergence in the present study, synchrony was less precise than with 5 mg E-17β; this is consistent with a previous study in which the administration of ECP to dairy cows resulted in relatively asynchronous follicular wave emergence [12]. In this regard, Bó et al. [16] reported delayed or asynchronous emergence of a new follicular wave when 5 mg EB (another estradiol ester) was administered. However,
Acknowledgements
Marcos Colazo was supported by FOMEC (Universidad de La Pampa, Argentina) and the University of Saskatchewan. The Saskatchewan Agriculture Development Fund, Strategic Research Program provided financial support. The authors thank Bioniche Animal Health for CIDR devices, Schering-Plough Animal Health for Estrumate, and Pharmacia Animal Health for Lutalyse. The authors also wish to thank Dr. Leonardo Brito, Dr. Cristal Deyo, Mr. Quinn Gavaga, Mr. Ken Piller (Neudorf, SK), Mr. William Kerr and the
References (28)
- et al.
Follicle wave emergence following treatment of CIDR-B implanted beef cows with estradiol benzoate and progesterone
Theriogenology
(1998) - et al.
The effect of estradiol benzoate administration on estrous response and synchronized pregnancy rate in dairy heifers after treatment with exogenous progesterone
Theriogenology
(1996) - et al.
Ovulatory responses and plasma luteinizing hormone concentrations in dairy heifers after treatment with exogenous progesterone and estradiol benzoate
Theriogenology
(1997) - et al.
Fixed-time artificial insemination in beef cattle using CIDR-B devices progesterone and estradiol benzoate
Theriogenology
(1999) - et al.
Effects of oestradiol cypionate on spontaneous and oxytocin-stimulated postpartum myometrial activity in the cow
Br. Vet. J.
(1990) - et al.
Effect of recombinant bovine somatrotopin on estradiol-induced estrous behavior in ovariectomized heifers
J. Dairy Sci.
(1992) - et al.
The influence of estradiol-17β and progesterone on peripheral serum concentrations of luteinizing hormone and follicle stimulating hormone on the ovariectomized ewe
Theriogenology
(1984) - et al.
Local versus systemic effect of exogenous estradiol-17β on follicular dynamics in heifers with progestogen implants
Anim. Reprod. Sci.
(2000) - et al.
Relationship between ultrasonic assessment of the corpus luteum and plasma progesterone concentration in heifers
Theriogenology
(1990) - et al.
Factors affecting the origin of the ovulatory follicle in heifers with induced luteolysis
Anim. Reprod. Sci.
(1991)
Effects of dose and route of administration of cloprostenol on luteolysis, estrus, and ovulation in beef heifers
Anim. Reprod. Sci.
Follicular wave dynamics after estradiol 17β treatment of heifers with or without a progestogen implant
Theriogenology
Estrus synchronization and pregnancy rates in beef cattle given CIDR-B, prostaglandin and estradiol, or GnRH
Can. Vet. J.
Induction of follicular wave emergence for estrus synchronization and artificial insemination in heifers
Theriogenology
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