78
46TH
ANNUAL
CONGRESS
OF
THE
SAEVA
SKUKUZA
16-‐20
FEBRUARY
2014
Study 1: Comparative study on the efficacy of native porcine zona
pellucida and recombinant zona pellucida vaccines in the mare.
Aims: This study will assess both the contraceptive and immunological potential of
a newly developed recombinant form of the vaccine (reZP) (Gupta et al. 2013), in
comparison to the conventional pZP vaccine in mares. This study also aims to
investigate ovarian function and follicular dynamics during ZP-based
immunocontraception in the mare by monitoring ovulation, oestrus cycle length and
ovarian steroid synthesis in mares treated with different ZP-based vaccines.
Methods: Reproductively normal Nooitgedacht pony mares (n=21) between 2-9
years of age were randomly assigned to 3 age-stratified groups. Group I (n=7)
receive an initial vaccination of 100 µg heat-solubilised pZP with adjuvant, followed
by a similar booster vaccination 5 weeks later. Group 2 (n=7) receive an i nitial
vaccination of 250- g reZP with adjuvant followed by a similar booster vaccination
5 weeks later. Group 3 (n=7), the control group will receive two treatments five
weeks apart, with the first treatment consisting of 1 ml PBS with adjuvant followed
by a similar treatment 5 weeks later. Mares are monitored daily by teasing and transrectal palpation and ultrasonography of the internal reproductive tract for 3
successive oestrous cycles commencing in October 2013. Breeding of all the mares
by fresh semen AI at an optimal stage of oestrus commenced in January 2014 (four
months after initial vaccinations). Mares are checked for pregnancy 14-16 days postovulation and following conception, mares are omitted from further study. Mares
found to be non-pregnant undergo up to two more AI’s over the course of the next
two oestrous cycles. Mares, which fail to conceive after three AI’s, will undergo no
further inseminations and will also be removed from the study.
Measurements:
a) Vital parameters (rectal temperature, heart rate, and respiratory rate) are
recorded to monitor general health,
b) Blood samples for ZP-antibody titres: collected prior to first treatment, at the
time of second treatment and monthly thereafter,
c) Blood samples for serum progesterone concentrations (SPC),
d) Blood samples for determination of serum oestrodiol-17β during oestrus and
e) Clinical oestrous cycle variables including follicular dynamics, endometrial changes
and interovulatory intervals
Conclusions
The immunisation of mares with a GnRH-vaccine resulted in an effective transient
suppression, and subsequent resumption, of cyclic ovarian activity. The significant
effect of age, particularly amongst the youngest mares, on the period to resumption
of cyclic activity must, however, be considered when considering this treatment
option in potential broodmares. GnRH vaccines offer a range of potential
applications in stallion management with benefits including enhanced economics,
welfare and treatment modalities.
The utilisation of the mare as an appropriate model for investigating improved
vaccine technologies for population control in large herbivores such as the African
elephant has great promise for improved efficacy, safety and widespread application.
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