Page 450 - Equine Clinical Medicine, Surgery and Reproduction, 2nd Edition

Reproductive system: 2.1 The female reproductive tr act 425

VetBooks.ir and fertile stallion can naturally cover 40–60 mares • Assess the presence of any intrauterine fluid
4–12 hours after mating using ultrasound
in one season, although in recent times the tendency
has been for Thoroughbred stallions to cover well
over 100–150 mares. This requires intensive ultra- examination. If a significant quantity of fluid
is present after 4 hours, the uterus should be
sound monitoring of the mares in advance of breed- lavaged using 1 litre of lactated Ringer’s solution
ing and post-breeding treatments to maximise the or 0.9% saline warmed to body temperature
fertility of each cycle and minimise the number of (37°C [98.6°F]) via an equine uterine lavage
coverings a stallion has to perform. catheter or soft tube. Lavage and siphoning
should be repeated a maximum of 3–4 times
MINIMAL-CONTAMINATION or until the flushing solution emerges clear
BREEDING TECHNIQUES of debris. If the pre-breeding endometrial
swab showed bacterial contamination, then
Overview an antibiotic solution may be infused after
During natural mating ejaculation occurs into the the last flushing depending on the culture
body of the uterus, leading to contamination of the and sensitivity results. The routine use of
lumen and inflammation of the cervix, vestibule, intrauterine antibiotics post breeding is
vagina and vulva. Techniques applied at mating are viewed as controversial and not best practice
aimed at reducing the pathogen challenge to, and any for appropriate antibiotic use. (Note: If
inflammatory reaction from, the intrauterine environ- oxytocin is to be administered intravenously,
ment in the pericoital period. These techniques help wait 30 minutes until myometrial activity has
to improve fertility rates in older multiparous mares, subsided before instilling an antibiotic solution.)
those with a history of endometritis and in mares Oxytocin administered intramuscularly or
mated at the foaling heat or to stallions infected with intravenously 4–8 hours after mating has
Pseudomonas aeruginosa or Klebsiella pneumoniae (not proved beneficial to conception rates in some
in the UK under the Horserace Betting Levy Board mares with a history of chronic endometritis.
Code of Practice). It should be considered sound ‘good It also stimulates the drainage of any residual
practice’ in any mating situation for minimising the intrauterine fluid, but it may increase the
possibility of infection and maximising fertility. likelihood of early embryonic death in some
susceptible mares.
Technique • The mare should be re-examined by
• One covering per oestrous cycle should ultrasound 24 hours later and the oxytocin
be performed, ideally 24 hours prior to injection repeated every 4–8 hours if required.
ovulation. If required, LH or deslorelin can be Uncommonly, the mare may require further
administered 24 hours prior to covering in order uterine lavages, particularly in those animals
to induce ovulation. with pre-existing issues such as cervical fibrosis
• Attend to general hygiene: bandage the tail; or poor lymphatic drainage.
wash the vulva and perineum of the mare (some
clinicians also wash the penis of the stallion) ARTIFICIAL INSEMINATION OF THE MARE
with clean water, preferably from a spray bottle
or from a disposable plastic liner in a bucket AI is regularly used in many types of horse and pony
(plastic bin liner) to avoid cross-contamination; to achieve a pregnancy. Some breeds, however, will
dry with a sterile paper towel. Do not use not register progeny bred by this technique. Three
chemicals or strong soaps/detergents, as these types of insemination are used in the horse:
can be spermicidal. In some situations it may be
necessary to use warmed semen extender with • Fresh +/- extender.
antibiotic into the uterus at covering. Mating • Chilled extended.
should be fully supervised. • Frozen extended.