Page 551 - Equine Clinical Medicine, Surgery and Reproduction, 2nd Edition

526 CHAPTER 2

VetBooks.ir Observation of libido and or ground collection, also develop an erection rap-
breeding behaviour
idly during their usual breeding routine; however,
Libido and behaviour are observed during the stal-
should exhibit a strong drive to mount the phan-
lion’s typical breeding routine. Sexually experi- the stimuli are stallion specific. These stallions
enced stallions used for breeding in hand will show tom or service the artificial vagina. Experienced
strong interest in a mare in oestrus. Vocalising and pasture-breeding stallions may appear to show little
prancing begin soon after the mare is visible. Most interest in breeding in an in-hand situation or when
stallions will approach the shoulder of the mare and the mare is not at the peak of oestrus. Additionally,
may sniff, then squeal and strike out. If the mare they test receptivity carefully by thorough teasing
is receptive, the stallion will move towards the and mounting without an erection. After mount-
mare’s hindquarters, nuzzling the flank and peri- ing, intromission of the penis into the vagina or
neal region before mounting. The time required to artificial vagina stimulates strong pelvic thrusting.
obtain an erection depends on the stallion’s previ- Ejaculation occurs rapidly, and consists of six to
ous breeding experience and temperament, but is eight strong urethral pulsations. After ejaculation,
normally less than 5 minutes. Stallions experienced the penis almost immediately becomes flaccid and
in collection for AI, either by mounting a phantom the stallion relaxes.

SEMEN COLLECTION AND EVALUATION

SEMEN COLLECTION internal temperature cools more quickly than other
types. The Colorado artificial vagina holds the tem-
Collection of semen from a stallion for evaluation or perature well, but it is heavy to use. Commercially
insemination is best accomplished through the use of available phantom mounts are designed in some
one of the commercially available models of artificial cases to have the Colorado device placed inside.
vaginas. The most common types in use include the This method offers the advantage of requiring one
Missouri style, the Colorado style and the Hanover less person (i.e. does not require a semen collec-
artificial vagina (Fig. 2.134). The Missouri artifi- tor) for the semen collection. However, this type of
cial vagina is light and easily handled; however, the set-up appears to place the stallion at higher risk of
traumatic injuries, particularly to the prepuce and
penis. Other methods of obtaining semen include
2.134 collection of a dismount sample, use of a condom
or other collection device in the mare, and phar-
macological ejaculation. The total number of sperm
in the ejaculate, however, can only be determined
following collection of the entire ejaculate with an
artificial vagina to allow measurement of both total
semen volume and sperm concentration. This is an
important consideration when a stallion is presented
for fertility evaluation. Raw stallion semen is very
fragile and poor handling can easily result in poor
motility, morphology and longevity. Rapid changes
in temperature and exposure to water, detergents,
lubricants or other chemicals all impact negatively
Fig. 2.134 The disassembled Missouri artificial on sperm survival (Fig. 2.135).
vagina, including the rubber liner, leather case with The artificial vagina is designed to hold hot water
handle, semen filter, collection bag and bottle. within a sealed jacket. The warmth and pressure