ResearchTiming of induction of ovulation in mares treated with Ovuplant or Chorulon☆,☆☆
Introduction
Although it has been shown that mares bred to fertile stallions can conceive even if ovulation occurs several days after breeding, conception rates increase significantly if the breeding takes place closer to ovulation.1 The reliability of inducing a timed ovulation in relationship to breeding becomes an important managerial tool when (1) mares are bred too highly booked stallions, and only 1 service per cycle is possible; (2) mares are bred to subfertile stallions whose sperm concentration is low or have poor sperm longevity; (3) mares must be bred only once because of delayed uterine clearance or susceptibility to uterine infections so that uterine contamination is reduced; or (4) mares are bred by artificial insemination with cooled transported or frozen semen because the number of shipments or insemination doses are often limited and semen quality is not optimal. Furthermore, limiting or reducing the number of inseminations per cycle will result in a more labor-efficient and cost-effective breeding operation.
Currently, there are 2 products commercially available to induce ovulation in the mare. Human chorionic gonadotropin (hCG) is a large glycoprotein with luteinizing hormone–like activity purified from the urine of pregnant women. Intramuscular or intravenous injection of 1,500 to 5,000 IU of hCG in mares displaying behavioral estrus and a follicle of at least 35 mm has proven effective in inducing ovulation.2 In addition to hCG, the gonadotropin releasing hormone (GnRH) analogue, deslorelin, or Ovuplant, has also been effective in inducing ovulation in mares that are displaying behavioral estrus with a follicle of 30 mm or greater.3, 4 Ovuplant is a small synthetic peptide that when implanted releases the active product over a period of 48 to 72 hours.3
Although hCG is effective in inducing ovulation, recent data indicates that the interval between treatment and ovulation when using hCG ranged between 12 hours to more than 48.5 In contrast, clinical impressions from practitioners have suggested that Ovuplant induces ovulation in what appears to be a very predictable time frame after treatment and that pregnancy rates of mares bred once or twice with frozen semen at fixed times after Ovuplant treatment appear to be comparable with no significant deleterious effect on pregnancy rates.6 Although ovulations induced by Ovuplant appear to occur around 24 to 48 hours, the precise ovulation time is not clear.
This study was designed to determine the precise timing of ovulation after Ovuplant treatment. In addition, we wanted to compare the distribution of the ovulations of normal cycling mares presented to the Veterinary Medicine Teaching Hospital for breeding and treated with Ovuplant or hCG (Chorulon). Pregnancy rates of mares bred with a single insemination of frozen or chilled semen at a fixed time after Ovuplant or hCG were determined. Based on previous observations,6, 7 we hypothesized that Ovuplant would have a reduced variation in the timing of ovulation induction compared with hCG.
Section snippets
Materials and methods
This study was conducted between May and July of 2001, at Kansas State University and complied with all criteria set by the animal use and care committee of Kansas State University.
Twenty-two quarterhorse (QH), 4 warmblood (WB), 4 thoroughbred (TB), and 2 Arabian mares were used for this study and were kept on pasture and supplemented with grass-alfalfa hay and minerals ad libitum or housed at the Veterinary Medical Teaching Hospital at Kansas State University. All mares were monitored for
Results
Average follicle size at the time of treatment for the hCG-treated mares was 40.5 ± 2.4 mm. and was not statistically different than that for the Ovuplant-treated mares (39.1 ± 3.7 mm.) (P > .05). Ovulation rate in response to Chorulon was 83.3% at 48 hours, 91.6% at 72 hours, and 100% at 96 hours. In contrast, all of the Ovuplant-treated mares had ovulated by 42 hours (Fig 1). Although there
Discussion
In brood mare practice, timing ovulations at a specific time is highly desirable and could have many advantages for the veterinarian and breeding farm manager. Benefits of inducing a timed and reliable ovulation include a reduction in the number of services per cycle in highly booked stallions, increased accuracy in the timing of breeding when using cooled shipped or frozen semen or stallions with poor sperm longevity, a reduction in the number of covers or inseminations of problem or difficult
Conclusions
This data shows that Ovuplant induces ovulation in a very narrow window (36-42 hours) when implanted using the criteria set in the present study. Although hCG-induced ovulation reliably in most mares, the distribution was much wider than those ovulations in mares treated with Ovuplant. Because of its predictability in the time it causes ovulation, Ovuplant could become a very important tool in the management of mares breed by artificial insemination with shipped or frozen semen, or by natural
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Cited by (27)
Increase of Body Temperature Immediately After Ovulation in Mares
2023, Journal of Equine Veterinary ScienceEffects of Equine Chorionic Gonadotropin on Ovulatory and Luteal Characteristics of Mares Submitted to an P4-Based Protocol of Ovulation Induction With hCG
2020, Journal of Equine Veterinary ScienceCitation Excerpt :The equine is a positive phototropic species in which increased luminosity has a positive effect on the pulses of hypothalamic gonadotropin-releasing hormone (GnRH) and gonadotropins secretion [9,10]. Hence, the breeding activity of the mare is mainly influenced by photoperiod, nutrition, and climatic factors [11]. Several hormonal treatments have been used to induce and/or synchronize the ovulation as it facilitates equine reproductive management, reduces animal handling, and increases the successful application of reproductive biotechniques [12].
Histrelin acetate-induced ovulation in Brazilian Northeastern jennies (Equus asinus) with different follicle diameters
2019, TheriogenologyCitation Excerpt :Ovulation induction is a methodology often used in mares [19–22] for predicting the best times for artificial insemination [23], which improves conception rates and enables the use of advanced techniques for assisted reproduction. Ovulation induction in mares is well established [24–26]. However, protocols for inducing ovulation in jennies are not well established yet.
What Are the Options for Induction of Ovulation in the Mare in Europe? Buserelin as an Alternative to Human Chorionic Gonadotropin
2017, Journal of Equine Veterinary ScienceEffect of Deslorelin and/or Human Chorionic Gonadotropin on Inducing Ovulation in Mares During the Transition Period Versus Ovulatory Season
2014, Journal of Equine Veterinary ScienceEfficacy of Deslorelin Acetate (SucroMate) on Induction of Ovulation in American Quarter Horse Mares
2012, Journal of Equine Veterinary ScienceCitation Excerpt :Historically, deslorelin acetate has been administered to mares in implant, slow release, aqueous, and lyophilized formulations with the intent to induce a timed ovulation [3-8]. Subcutaneous administration of a sustained release implant containing 2.1 mg of deslorelin acetate (Ovuplant; Fort Dodge Animal Health, Fort Dodge, IA) was reported to induce ovulation in approximately 40 hours [2,9]. However, limited clinical data have been published on the recently approved deslorelin product.
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Address reprint requests to Juan C. Samper, DVM, PhD, Department of Clinical Sciences, 1800 Dennison Avenue, Manhattan, KS 66506.
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Refereed