Abstract
Simple SummaryDue to the breeding success of common marmosets in captivity, colony managers need to achieve a balance between maintaining sustainable population numbers while preventing the breeding of surplus animals. Population control can be achieved by various methods, reversible and nonreversible. Long-acting reversible contraceptives are preferred, as they are not permanent and eliminate the logistical problems associated with the daily or weekly administration of oral or injectable contraceptives. Implanon® (etonogestrel) is a widely used progestin-based contraceptive in marmosets with the theoretical advantages of being reversible and long-acting. However, no dose and efficacy data are available yet. In this study, we examined, by using electronic health records, the relationship between the use of one-fourth or one-third of an etonogestrel implant in female marmosets and the number of parturitions, interbirth interval, litter size, body weight, stillbirths and unintended pregnancies. We have concluded that etonogestrel implants are efficacious and safe to use in marmosets. Our data result in recommendations about the use of etonogestrel implants in marmosets. Our data can probably be extrapolated to other callitrichids.Contraception is an important population control method for the colony management of primates housed in captivity. Etonogestrel (ENG) implants (i.e., Implanon®) are a widely used progestin-based contraceptive in common marmosets (Callithrix jacchus) with the theoretical advantages of being reversible and long-acting. However, no dose and efficacy data are available yet. Therefore, data from 52 adult female marmosets contracepted with ENG (one-fourth or one-third of an implant) housed at the Biomedical Primate Research Centre (BPRC, Rijswijk, The Netherlands) over the past 18 years were analyzed. Using an electronic database, a retrospective longitudinal cohort study was conducted to calculate the reproductive data before, during and after ENG use. The data show an effectiveness in preventing pregnancy of 99%. The implant was effective within one week after insertion. Unintended pregnancies did occur, but in 60% of these cases, the animals were already pregnant at the time of implant insertion. In these cases, healthy offspring were born despite the use of the implant. No stillbirths, neonatal deaths or maternal deaths could be linked to ENG use. After implant removal, 83% of the animals delivered healthy offspring. No difference in contraception efficacy was observed between the use of one-fourth or one-third of an implant. ENG achieved a contraceptive protection exceeding 99% and was shown to be reversible concerning fertility. To our knowledge, this is the first detailed analysis on the use of ENG in marmosets.
Highlights
The common marmoset (Callithrix jacchus) is a New World monkey whose natural habitat is the Atlantic coastal rainforests of Northeastern Brazil
Prior to the introduction of contraception, the used methods included the housing of sexes separately, transfer of animals to other institutions and zoos and euthanasia of surplus animals
The dataset consisted of a total of 52 captive-born female common marmosets (Callithrix jacchus) and included data on body weight, age, date of parturitions, litter size, still births and abortions, date of implant insertion and removal and the results of pathology
Summary
The common marmoset (Callithrix jacchus) (hereafter, “marmosets”) is a New World monkey whose natural habitat is the Atlantic coastal rainforests of Northeastern Brazil. Marmosets have the highest potential fecundity of any anthropoid primate [3,4,5]: marmosets usually give birth twice a year (mostly twins and triplets), show no seasonal limitations, have a relatively short gestation period of approximately 144 days [6], have a fertile postpartum ovulation and reach sexual maturity at about 18 months of age [7] Due to their breeding success, colony managers need to achieve a balance between maintaining sustainable population numbers while preventing the breeding of surplus animals. Reversible contraceptives are available, which are the perfect tool for applying balanced population control Hormonal substitution methods such as birth control pills and implants are commonly used in exotic species housed in zoos (EAZA Group on the Zoo Animal Contraception website, 2021; https://www.egzac.org/; accessed on 1 March 2021). In an effort to fill this gap of scientifically reported knowledge, a retrospective data analysis was performed, including effectiveness, reversibility and the side effects of a one-fourth to one-third part of subcutaneously (SC) inserted ENG implants in common marmosets housed in captivity
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