Stress and reproduction in domestic cats (Felis catus) as a model for endangered felids : a thesis presented in partial fulfilment of the requirements for the degree of Doctor of Philosophy (Ph.D.) Animal Science Group, Massey University, Palmerston North, New Zealand
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Date
2021
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Massey University
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Abstract
Captive breeding programs are a vital component of the conservation strategies for felids, but these programs are often hindered by poor reproductive performance. Knowledge of reproductive biology is crucial to improving in situ and ex situ felid breeding programs. This thesis provided the first comprehensive systematic review of the literature available on the reproductive biology of the extant felid species. It was concluded that the high prevalence of teratospermia and highly variable oestrous cycles in felids contribute towards their poor reproductive performance in captivity. The captive environment has been linked to reduced ejaculate quality and ovarian quiescence in felids, but it is difficult to elucidate whether this is due to captivity-related stress (i.e., elevated glucocorticoid (GC) concentrations) or other factors associated with captivity. This thesis aimed to determine whether a simulated endocrine stress response (GC treatment) altered the testicular and ovarian function of felids using the domestic cat as a model species. While epididymal sperm motility was unaffected by GC treatments, the percentage of morphological abnormal sperm was higher in GC-treated cats than in control cats. This would likely have an adverse effect on fertility as morphologically abnormal sperm are rarely involved in the fertilisation process. Glucocorticoid treatments did not affect the ovarian response of cats in which follicular growth and development was stimulated by exogenous gonadotrophins. However, ooplasm and zona pellucida morphology was graded poorer in GC-treated animals than control animals. Whether this corresponds to a reduction in fertility is unclear as the fertilisation capabilities of oocytes were not assessed. It would be worth investigating whether GC administration affects the natural oestrous cycles of cats, as elevated GC concentrations associated with captivity have been linked to ovarian quiescence. However, this would require an accurate and minimally invasive (i.e., low stress) method for monitoring the ovarian cycles of domestic cats. Thus, this thesis investigated whether accelerometry and infrared thermography could be used to monitor the ovarian function of cats. It was found that accelerometry could be used to detect an increase in activity of cats following the induction of follicular growth with equine chorionic gonadotrophin (eCG). Infrared thermography also identified changes in perivulvar temperature (PVT) driven by follicular development and ovulation, with PVT increasing as follicular growth occurred and decreasing following ovulation. Both methods show promise; however, further investigation into the use of accelerometry and IR thermography for monitoring ovarian function is needed. In conclusion, the results of thesis indicate that GC have adverse effects on the testicular and ovarian function of domestic cats. Thus, there is an urgent need to further investigate the effects of captivity-related stress on the reproductive performance of non-domestic felids. Furthermore, this thesis assessed two promising non-invasive methods for monitoring the ovarian activity of cats, with the findings being highly applicable for the management and breeding of non-domestic felids in captivity.
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Listed in 2021 Dean's List of Exceptional Theses
Figure 1 (=Johnson et al., 2006 Fig. 1) was removed for copyright reasons but may be accessed via https://www.jstor.org/stable/3843306 Also removed were published articles comprising Appendix 1 and Appendix 2 as they are are copyrighted to their publishers.
Figure 1 (=Johnson et al., 2006 Fig. 1) was removed for copyright reasons but may be accessed via https://www.jstor.org/stable/3843306 Also removed were published articles comprising Appendix 1 and Appendix 2 as they are are copyrighted to their publishers.
Keywords
Dean's List of Exceptional Theses, Cats, Reproduction, Effect of stress on, Infertility