OVULATION WITHOUT CERVICAL STIMULATION IN DOMESTIC CATS

Progesterone was measured by radioimmunoassay of serum collected at mo nthly intervals for 9 months (April-December) in 24 adult female Ameri can shorthair cats (age 2.5-11 years, mean 7.4 years); 20 cats were in tact, and four were ovario-hysterectomized controls. One of the 20 int act queens was ovariohysterectomized after 7 months, when pyometra was diagnosed. Cats could see and hear one another, and could see and hea r male cats housed individually in the same room. Direct contact with other cats was prevented. Tactile stimulation of the cats' hindquarter s and perineal regions by handlers was avoided. Serum progesterone con centration greater-than-or-equal-to 4.8 nmol l-1 was defined as eviden ce of ovulation. This concentration was exceeded in seven of 20 intact queens (35%) at one or more occurrences of non-coital ovulation; ther e were 13 such occurrences in all (1-3 per queen). Serum progesterone concentration ranged from 0.2 to 103.4 (mean 14.09 +/- 2.0) nmol l-1 i n these seven cats, and was significantly greater than concentrations in the other intact and neutered cats. In the remaining 13 intact and four ovariohysterectomized cats, serum progesterone concentrations ran ged from 0.2 to 3.2 (mean 1.24 +/- 1.46) nmol l-1. These data suggest that, at least as far as cats housed in proximity to one another are c oncerned, intact female cats do not always require cervical stimulatio n to induce ovulation.