Manipulation of reproductive functions in male and female New World camelids

Abstract

Although most of the information comes from research on alpacas, there is evidence that the four species of New World camelids (alpaca, Ilama, guanaco and vicuña) share common reproductive characteristics. Females, after reaching puberty at about 1 year of age, do not show a definite pattern of estrous cycles. During the breeding season they show continuous estrus interrupted by short periods of non-receptivity. Copulation takes place in a recumbent position and may last from 10 to 50 min. Ovulation is induced and occurs about 26 h after copulation. In the absence of gestation the corpus luteum has a lifespan of about 13 days. Both ovaries are equally active in the production of ova; however, more than 90% of embryos are located in the left uterine horn. Multiple ovulations occur in about 10% of cases, but multiple births have not been reported. The breeding season in the natural habitat is confined to the rainy months (January–April); however, when males and females are kept separately they show sexual activity all year round. Mean gestation lengths vary from 342 to 350 days. Females may show estrous behavior as soon as 24 h after parturition, but fertile mating may not be possible until about 15 days post partum. Estrous behavior of females in response to males is a reliable method of pregnancy diagnosis. Other methods such as rectal palpation and circulating progesterone levels are also effective. Early embryo mortality appears to be one of the main factors leading to low reproductive efficiency. Studies on male reproduction are more limited than in the female. The lack of a reliable semen collection technique has been one of the limiting factors for studies on semen characteristics and the use of artificial insemination. Even though males start showing sexual desires as early as 1 year of age, normal copulation is not possible since shedding of the penopreputial adhesions does not occur until at least 2 years of age. Some studies on spermatogenesis, semen collection techniques and semen characteristics in Ilamas and alpacas are described. Also, reference is made to artificial insemination and embryo transfer trials carried out in alpacas and vicuñas with limited success. Research priorities to obtain a more thorough understanding of the reproductive biology of these species are also pointed out.