Page 448 - Equine Clinical Medicine, Surgery and Reproduction, 2nd Edition

Reproductive system: 2.1 The female reproductive tr act 423

VetBooks.ir If the mare is bred at foal heat it is essential that • Ovulation at preferably >10 days post foaling
(minimum of 8 days).
the embryo enters a uterus that is fully recovered,
and given that the embryo passes into the uterus
4–5 days after ovulation, the mare should not be • Intensive post-breeding treatment may be
appropriate (e.g. intrauterine antibiotics,
covered prior to 10 days following a normal foaling intravenous oxytocin +/- uterine lavage to
(10 days + 4 days = 14 days) so that the fertility of improve pregnancy rates at the foal heat).
foal heat is maximised. Owners may wish to try and
cover a foaling mare on the foal heat to gain time PGF α administration
2
in the race against the January 1st or August 1st PGF α can be used to shorten the first luteal phase
2
deadline. It therefore makes good sense to monitor in mares that are not ideal for mating on or around
mares individually 7 days after foaling by vaginal day 10. It can be given to mares 5 or 6 days after
speculum examination, rectal palpation and ultra- ovulation when the exact dates are known, or on or
sound to select those capable of being bred on the around day 20 post foaling to bring them back into
foal heat. It should be appreciated that mares in foal oestrus 3–4 days post injection.
from being bred at foal heat have a slightly increased
pregnancy failure rate when compared with mares Delaying the first post-
bred at the second oestrus or those that are short partum ovulation
cycled. The criteria used to help decide whether to Progesterone or altrenogest alone (or in combina-
cover a mare at foal heat include: tion with oestradiol) can be used to delay the first
ovulation. Although it can be given from day 1 post
• Normal foaling. partum, it is preferable to start from around day 4
• No retained placenta or history of metritis or to allow some uterine involution and recovery. By
endometritis. delaying the first ovulation beyond day 10 the preg-
• No cervical, vaginal or vulval damage. nancy rates are improved for mares bred at foal heat.
• Normal uterine involution. This technique is not always successful.

BREEDING MANAGEMENT

Mares can be bred naturally by a stallion or artifi- stallion can be used. Teasing is performed every
cially inseminated using either fresh or preserved 1–2 days and records made of the mare’s response.
semen (chilled or frozen). Furthermore, the use of a teaser stallion allows the
stud to confirm the mare will display the appropriate
NATURAL MATING behaviour for breeding before exposing her to the
covering stallion, thus minimising the risk of injury
Mating can occur free with the mare and stallion in a to the stallion. The requirements are:
yard or at grass, and this is a system still used at some
stud farms, particularly in ponies. There is often • A good teaser stallion(s).
minimum input by the stud staff or veterinarian. • A teaser system suited to the farm’s management
A supervised mating system is used for the major- system and the individual mare.
ity of stud farms using natural mating and is the • An experienced observer and recorder.
only system permissible in the Thoroughbred if the
resulting progeny are to be registered (Fig. 2.23). Some breeding operations do not use veterinary
Detecting whether a mare is in oestrus can be car- monitoring of the mares and rely only on how the
ried out by ultrasound examination alone or, to min- mare behaves towards the stallion. This can be
imise veterinary examinations and costs, a teaser labour intensive and require multiple matings per