Page 972 - Small Animal Internal Medicine, 6th Edition

944 PART VIII Reproductive System Disorders

90% to 100% superficial cells should be present. If clients
delay in bringing dogs to the veterinarian for assistance with
VetBooks.ir 0 breeding until after several days of failed attempts, vaginal
cytology must still be performed to confirm the bitch is still
in estrus. Progesterone testing will then confirm whether she
1 is postovulatory and breeding is timely, but an initial arti-
LK ficial insemination is advised while awaiting progesterone
results. A shift to less than 50% superficial cells indicates
2
diestrus has begun. Only intrauterine inseminations per-
L OVARY formed on the first day of diestrus have been successful in
3 producing pregnancy.
When increased accuracy of ovulation timing is necessary
(i.e., for frozen semen breedings or breedings with subfertile
4
stud dogs or brood bitches), LH testing is recommended.
Once the LH surge is identified, breeding days may be
planned. The day of the LH surge is also day zero. Two
FIG 54.19 natural, fresh, or chilled semen artificial breedings are
Normal sagittal canine left ovary in the luteal phase of the advised from days 3 through 6. Frozen semen inseminations
estrous cycle. The corpora lutea have thicker walls (cursors)
and anechoic contents, and will persist for >45 days are advised on day 5 or 6 of the fertile window owing to the
postovulation. LK, Left kidney. short life span of cryopreserved thawed sperm. In addition,
at least one progesterone assay should be performed after the
LH surge is identified to document that progesterone levels
continue to rise and are above 5.0 ng/mL before breeding. If
CLINICAL PROTOCOL: VETERINARY client economics dictate minimal testing, serum can be
BREEDING MANAGEMENT batched on a daily basis and quantitative progesterone tests
Clients usually delay breeding the maiden bitch until after performed initially as advised earlier. When the initial rise
2 years of age for ethical reasons and to complete genetic in progesterone is identified, the batched serum can be spe-
screening; bitches are physiologically capable of breeding in cifically evaluated for the day of the LH surge, confirming
their first estrous cycle. Breeder clients should be advised identification of day zero.
to notify the clinic when they first notice a bitch for which Clinicians may be questioned about using vaginal glucose
timing is planned is in season, based on vaginal discharge content and electrical conductivity for ovulation timing.
or vulvar swelling/attraction to males. Even the most astute Increased glucose has been identified in vaginal secretions
owner can fail to notice the true onset of proestrus for a as an inconsistent finding; it is thought to be a result of
few days, so early clinical evaluation (on day 3-5 after the insulin antagonism that occurs secondary to altered hormone
onset of the heat cycle) with vaginal cytology is advised. The concentrations at the time of the progesterone rise. This
type of breeding anticipated should be determined because finding is not reliable, however, and is not recommended for
it dictates the types of testing to be done. Early proestrus ovulation timing. Measurement of electrical conductivity of
should be documented by vaginal cytologic analysis (<50% vaginal mucus is used routinely to time breedings in foxes
cornification/superficial cells). A baseline progesterone and has been studied in several other species, including the
level might be informative if the true onset of the cycle is dog. It was found that electrical resistance increases as estrus
unknown (baseline is < 1.0 ng/mL). Vaginal cytology should approaches and then plateaus at a maximal level for several
be performed every 2 to 4 days until a significant progression days, changes that may be due to rising estrogen. Although
in the percent of superficial cells is seen, usually above 70% it appeared that ovulation occurred at some point during this
superficial cells. At that point, appropriate serial hormonal period of maximum electrical resistance, it has not been
assaying should begin. For routine breedings (natural, fresh, shown to be correlated to the LH surge or the fertile period,
or fresh chilled artificial insemination with fertile dogs), so it cannot be recommended for accurate ovulation timing.
progesterone testing may be done every other day until a Ovulation timing is not usually performed in the queen
rise in progesterone above 2.0 ng/mL is identified. The day whose estrual behavior is obvious; in fact vaginal swabbing
of the initial rise in progesterone is identified as “day zero.” can induce ovulation. Estrus cytology in the queen is similar
Two natural breedings or artificial inseminations are advised to the bitch, but superficial cells retain their nuclei (Fig.
between days 3 through 6, ideally 48 hours apart. Which 54.20). Serum progesterone can be used to confirm ovulation
2 days are chosen depends upon overnight chilled semen if >5.0 ng/mL.
shipping options and the involved clients’ and veterinarians’ Behavior and other observations (flagging, attractiveness
schedules. As described, confirmation of progesterone rise to males) should also be made at each examination, but less
above 5.0 ng/mL by the time of breeding is optimal. Vaginal weight should be put on these parameters (Videos 54.1 and
cytologic examination should always be performed on the 54.2). The clinician should keep in mind that the most accu-
day of artificial insemination to confirm previous timing; rate ovulation timing occurs when information from several