Case 3: Breeding management in a bitch

CASE 3: Breeding management in a bitch

Case Information:

A 6-year-old, intact female English Cocker Spaniel was presented for breeding management prior to artificial insemination with fresh semen. She had first been observed to be in heat, characterized by swelling of the vulva and exudation of bloody vaginal discharge, 8 days prior to presentation. Vaginal cytology on the day of presentation was completely non-cornified and white blood cells were present.

Question:

What stage of her cycle is indicated by the above vaginal cytology?

Answer:

This dog could be early in proestrus or just out of heat, in diestrus.

The canine heat, or estrous cycle, has four stages. Proestrus is the first stage, when the dog first exhibits vulvar swelling and bloody vaginal discharge. The male is interested but the female does not allow him to mount. Estrus, or standing heat, is the second stage, characterized by the female allowing the male to mount and breed. Diestrus is the two month stage after standing heat during which all dogs, even those that were not bred, undergo hormonal changes of pregnancy. The fourth stage is anestrus, the long stage between active signs of heat.

Vaginal cytology changes in a characteristic way as dogs progress through their heat cycle. Early in proestrus, all the vaginal cells collected on a swab are non-cornifed, or round and healthy. White blood cells can move easily through the thin vaginal wall and often are collected on the swab. As dogs near estrus, or standing heat, a greater proportion of their vaginal cells are cornified, or deadened. These cells appear misshapen. White blood cells rarely are seen during estrus, since the vaginal lining is very thick at this stage. When dogs finish their time of standing heat and enter diestrus, they abruptly slough off all the cornified cells and return to a non-cornified smear with many white blood cells. The vaginal cytology of early proestrus and early diestrus is identical.

Case Outcome:

To differentiate early proestrus from diestrus in this dog, the hormone progesterone was measured in blood. Progesterone concentrations are low in proestrus, rise just before or during estrus, and remain high throughout diestrus. Serum progesterone concentration in this dog was 0.4 ng/ml; she was in early proestrus on the day she was seen.

The serum progesterone concentration was rechecked five days later and was 5.7 ng/ml, which is indicative of ovulation. She was artificially inseminated with good quality semen two days after ovulation. Vaginal cytology was completely cornified, with the majority of cells appearing anuclear, at the time of artificial insemination.