Dog Owner's Home Veterinary Handbook.pdf - Mr. Walnuts

452 •DOG OWNER’S HOME VETERINARY HANDBOOK
progesterone. The administration of progesterone and androgenic drugs produces
a similar effect. Hypothyroidism and Cushing’s syndrome also produce
prolonged anestrus.
Hypothyroidism can be diagnosed by a thyroid blood test. Cushing’s syndrome
generally occurs in older females and is not a common reproductive
problem.
Bitches with normal ovaries who are slow to come into heat will often do so
when they are kenneled with other cycling females and regularly exposed to a
male. If this is not successful, and the bitch has a low serum progesterone level
and no discernible medical cause for the prolonged anestrus, consider karyotyping
to rule out intersex. If the karyotype is normal, an attempt can be made
to induce estrus and ovulation, as described on page 450 for Absent Heat.
Shortened Interestrous Interval
In bitches with this condition, the interval between one cycle and the next is
four months or less. A shortened interestrous interval should be distinguished
from split heat, in which the first cycle does not progress beyond proestrus,
and thus is incomplete.
The problem with a shortened interval is that the lining of the uterus has
not had sufficient time to repair the progesterone-induced damage caused by
the previous heat cycle. Thus, the endometrium is not hormonally receptive
to embryo implantation and the bitch with a shortened interestrous interval
cannot become pregnant.
Treatment may not be necessary. Most young females develop normal
interestrous intervals as they mature. In a mature bitch with a shortened
interestrous cycle, the process of uterine repair can be expedited by using an
androgen to terminate heat before ovulation, thus paving the way for a normal
endometrium on the next heat cycle.
Premature Ovarian Failure
Ovarian function begins to decline at about 6 years of age and ceases, on average,
when a bitch is 10 years old. This usually is not a problem, because most
bitches are not bred beyond 7 to 8 years of age. The ovaries of some bitches,
however, may cease to function as early as 6 years of age, resulting in permanent
anestrus. This can be confirmed by FSH and LH concentrations; both
will be extremely high in premature ovarian failure. There is no treatment for
premature aging of the ovaries.
FETAL LOSS DURING PREGNANCY
Early embryonic loss may take place even before the embryos implant in the
lining of the uterus because of unfavorable environmental conditions caused
by endometritis or cystic endometrial hyperplasia. Other causes of early