Reproduction, Fertility and Development
Number 8 2012
African elephants in zoos are not reproducing well, and many exhibit abnormal reproductive cycles, due in part to a condition known to cause infertility in women: hyperprolactinaemia. This study compared rates of hyperprolactinaemia with data collected 7 years prior, and found that the incidence has increased from one-third to two-thirds of acyclic females. We conclude that creating a self-sustaining population of African elephants will not be possible until we identify causes of hyperprolactinaemia and develop therapies to treat this serious fertility problem.
The relationship between the immune response and normal physiological processes such as involution in cattle is poorly understood. In this study we characterise the postpartum immune response at both a cellular and a molecular level in healthy cows. Our results show that postpartum inflammation and immune activation is not necessarily pathological and we speculate that dysregulation of this response determines susceptibility to uterine disease and sub-fertility in cattle.
The number of lambs born is limited by ovulation rate and embryo mortality, both of which are limited by the level of nutrition. However, supplements that increase ovulation rate might also increase embryo mortality. We tested this hypothesis and found that feeding lupin grain for 2 weeks after mating increased embryo survival, but sudden withdrawal of the supplement increased embryo mortality.
In pigs, oxidative stress effects the success rate of IVF and embryo development in vitro, but the methods used to reduce stress are not completely understood yet. The current study indicated that supplementing oocytes prior to fertilisation with the antioxidant n-acetyl-l-cysteine improves IVF and embryo development success. These findings emphasise the importance of reducing oxidative stress using antioxidant supplementation during the in vitro production of pig oocytes.
The mechanisms causing the positive influence of very short-term nutritional supplementation on ovulation rate and prolificacy still need to be fully elucidated. The present study shows that glucogenic treatment in sheep modifies follicle and corpus luteum functionality, and improves oocyte quality. This finding is important for determining the intrinsic effect of high-energy diets on prolificacy and sets the basis for adapting nutritional supplementation in protocols for assisted reproduction.
C-Type natriuretic peptide (CNP), a growth factor involved in fetal–placental growth and development, appears to be tightly regulated during ruminant pregnancy. In the present study of pregnant ewes, it was found that a period of fasting in late gestation increased CNP concentrations in maternal blood, likely reflecting increased production by the placenta. These results indicate that CNP production is acutely sensitive to dietary restriction during pregnancy and could thus be used to monitor nutrient supply to the fetus.
Oestrogen production by the trophoblast of the early equine conceptus is important for the establishment of pregnancy but its specific role(s) has not been defined. Having shown that the embryo proper can metabolise oestrogens, the present study sought to determine whether it could also biosynthesise them. Positive findings in this investigation are of interest in relation to the well recognised role of oestrogens in blood cell and blood vessel development.
Cryopreservation of germplasm is widely used in breeding programs for many valuable agricultural species, although the honey bee remains a notable exception. In this study, honey bee semen was cryopreserved and used to inseminate sequential generations of queens. This work demonstrates the potential utility of cryopreservation in honey bee breeding programs, and in the conservation of unique genetic lines and threatened subspecies.
Individual bovine in vitro embryo production can serve many purposes but is not a routine procedure due to low embryo numbers and quality, compared to group production. Individual embryo culture was optimised by the establishment of an oil-free, cell-free, semi-defined protocol leading to high embryo rates. The elucidation of specific needs of an individually growing embryo further unravelled the interactions between an individually developing embryo and changing culture conditions.
Ovulation in camelids is induced by a previously unidentified seminal plasma protein. The aim of the present study was to identify the protein that induces ovulation and to investigate its potential to induce ovulation in camelids. β-Nerve growth factor (β-NGF) was abundant in alpaca seminal plasma and induced ovulation in four of five female alpacas. This is the first study to identify β-NGF as the ovulation-inducing factor in camelids and this finding may lead to new methods for the induction of ovulation in camelids.
Embryonic stem (ES) cells require many growth factors for their survival and maintenance, many of which come from feeder layers on which the ES cells are cultured. We showed that genes expressing ACTIVIN-A, TGF-β1, BMP-4, gremlin and FGF-2 are expressed and that ACTIVIN-A and TGF-β1 are secreted by a buffalo fetal fibroblast feeder layer. This suggests that feeder cells produce signalling molecules that may help in the self-renewal of buffalo ES cells.
Artificial insemination has considerable potential for the genetic management of captive Asian elephants. We demonstrate that a semen extender designed to prevent oxidative damage (Bullmax) preserves sperm DNA integrity better than a conventional extender (TEST), at 4°C or 15°C. Moreover, sperm DNA stability during incubation at 37°C proved to be a promising parameter for determining whether bulls or storage conditions were suitable for semen preservation.
The spiny mouse is a unique rodent, giving birth to 1–4 pups of precocial nature after a relatively long gestation (39 days). We have developed for the first time, a superovulation protocol for the spiny mouse which elicits a 5-fold increase in the natural ovulation rate of this species. This technique will allow us to compare spiny mouse embryo development to other species and assess its usefulness as a model of early human pregnancy.
In the present study, we analysed for the first time the impact of pregnancy on thymocyte subpopulations in a mouse model. The findings show that the maternal thymus is aware of the pregnancy status and responds to it by modifying the proportion of lymphocyte subsets according to the male component of the cross-breeding and the pregnancy outcome. These effects may participate in the maintenance of maternal–fetal tolerance.
Poor survival of spermatozoa following freezing has been a major impediment towards establishing sperm banks (sperm repositories) for the endangered Asian elephant. The present study demonstrates that modification of Asian elephant sperm membranes using cholesterol-loaded cyclodextrins prior to freezing results in improved post-thaw sperm survival. This has major implications for species conservation by facilitating the establishment of a sperm bank and enhanced genetic management of the Asian elephant.