Page 967 - Small Animal Internal Medicine, 6th Edition

CHAPTER 54 The Practice of Theriogenology 939

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FIG 54.4
Proestrus vaginal cytology, showing intermediate cells and
red blood cells, with numerous extracellular opportunistic
bacteria.

FIG 54.6
Vulvar appearance,estrus.

FIG 54.5
Vaginoscopic appearance of edematous vaginal folds
during proestrus.

tends to be maximal (Fig. 54.6). Vaginal cytology remains
predominated by superficial cells; RBCs tend to decrease but
may persist throughout (Fig. 54.7). Vaginal mucosal folds
become progressively wrinkled (crenulated) in conjunction
with ovulation and oocyte maturation (Fig. 54.8). Estrogen
concentrations reduce markedly after the LH peak, while FIG 54.7
progesterone concentrations steadily increase (usually Estrus vaginal cytology, showing superficial cells with both
4-10 ng/mL at ovulation), marking the luteal phase of the pyknotic nuclei and anuclear cells.
ovarian cycle. Estrus lasts 3 days to 3 weeks, with an average
of 9 days. Estrous behavior may precede or follow the LH
surge; its duration is variable and may not coincide precisely cytology is abruptly altered by the reappearance of parabasal
with the fertile period. Ovulation of primary oocytes occurs epithelial cells and frequently neutrophils (Fig. 54.9). The
2 days after the LH surge; oocyte maturation occurs 2 to 3 appearance of vaginal mucosal folds becomes flattened and
days later. The life span of secondary oocytes is 2 to 3 days. flaccid. Estrogen concentrations are variably low, and pro-
During diestrus, the normal bitch becomes refractory to gesterone concentrations steadily rise to a peak of 15 to
breeding, with diminishing attraction of male dogs. Vulvar 80 ng/mL before progressively declining in late diestrus.
discharge diminishes and edema slowly resolves. Vaginal Progesterone secretion is dependent on both pituitary LH