Pregnancy-specific elevations in fecal concentrations of estradiol, testosterone and progesterone in the domestic dog (Canis familiaris).

Estradiol (E2), testosterone (T) and progesterone (P4) concentrations were determined by enzyme-immunoassay in aqueous extracts of fecal samples obtained during anestrus, proestrus, estrus and metestrus of 11 nonpregnant and 11 pregnant bitches. Fecal hormone concentrations (ng/g) changed in relation to stage of cycle. Mean fecal steroid concentrations in 22 anestrous bitches and 3 ovariectomized bitches were low and similar for E2 (53 +/- 5 and 27 +/- 2), T (60 +/- 7 and 36 +/- 6), and P4 (62 +/- 6 and 86 +/- 15). Within 0 to 3 d of the ovulatory LH surge fecal E2 reached peak concentrations (301 +/- 38). The T peaks (281 +/- 41) were coincident or 1 to 3 d later. Fecal P4 was then elevated for approximately 2 m.o. Between Days 26 and 45 after ovulation, mean fecal P4 concentrations were higher (P < 0.05) in pregnant (401 +/- 60) than in nonpregnant bitches (164 +/- 23) and peak fecal P4 concentrations in individual animals were higher (P < 0.01) in pregnant (812 +/- 121) than in nonpregnant bitches (425 +/- 97). In the same period mean concentrations of E2 (117 +/- 13 vs 61 +/- 5) and T (102 +/- 10 vs 70 +/- 6) were also higher (P < or = 0.05) in pregnant than in nonpregnant bitches. Serum E2, T and P4 concentration were positively correlated (P = 0.1) with concentration in fecal samples obtained one day after serum collection. Although serial fecal ovarian steroid concentrations demonstrate the time course of ovulatory cycles, the diagnostic value of individual fecal samples appears limited. The ratios of peak to basal values were approximately 6, 5 and 7 for E2, T and P4, respectively, and were considerably lower than ratios of 12 to 50 previously reported for serum or plasma concentrations. The results demonstrate that there are pregnancy-specific increases in P4, E2 and T production reflected in fecal concentrations. While such increases are reflected in fecal samples, they are generally not evident in serum or plasma concentrations because of increased hemodilution, metabolism and clearance in pregnant bitches. The physiological stimulus for these increases, presumably ovarian in origin, or the potential role of prolactin is not known.

Incidence of spontaneous ovulation in young, group-housed cats based on serum and faecal concentrations of progesterone.

Cats are considered to be reflex ovulators that exhibit a luteal phase (pregnancy or pseudopregnancy) only after copulatory stimulation. In a group-housed colony of 15 1-year-old domestic queens, 23 noncopulatory, spontaneous ovulations were observed in 87% of the queens over 4.5 months based upon the detection of increased concentrations of progesterone in faeces, serum, or both. Luteal phases were detectable for periods of 3 to 5 weeks with peak progesterone concentrations averaging 21 +/- 1 ng ml-1 in serum and 1874 +/- 281 ng g-1 in faeces. Individual cats exhibited from 0 to 3 spontaneous ovulations and subsequent pseudopregnancies each. A male was added to a separate cage within the room during the last 1.5 months of the study. The incidence of ovulation per 10 day period ranged from 0% to 22% before introduction of the male and from 33% to 57% immediately after introduction of the male, suggesting a potential noncopulatory influence of the male on the incidence of spontaneous ovulation in young, group-housed cats.

Social influences on reproductive development and fertility in female Djungarian hamsters (Phodopus campbelli).

Social influences on the sexual maturation of female Djungarian hamsters were investigated in two experiments. In the first experiment females were housed from weaning with an adult male, by themselves, or with a weanling sister. Maturation was accelerated in females housed with males as indicated by younger age at first ovulation, increased rates of ovarian and uterine growth, and lower LH levels at some ages. Maturation was delayed in females housed with sisters compared to those housed alone as measured by time of first ovulation and by lower estradiol levels at some ages. The most marked differences between groups occurred 8 to 12 days after weaning, suggesting that events during this period are particularly important in the social mediation of sexual maturation. In the second experiment the effects of reproductive suppression (caused by living with a sister) on the subsequent fertility of females housed with males were examined. If male-female pairs were housed in clean cages, no effects were observed; however, pairs housed in cages previously soiled by the female and her sister had fewer young surviving until 1 week of age despite no differences in the age of pregnancy onset or in the initial litter size. Thus, even cues present in unrenewed soiled bedding may have subtle but long lasting effects on reproductive function.

Suppression of postpartum fertility in pairs of female rats sharing the same nesting environment.

The probability that a successful pregnancy will follow postpartum estrus in the rat is significantly reduced when the postpartum female is housed with another female that is both pregnant and lactating. We studied 16 pairs of females, each pair maintained in a separate nesting environment containing a sexually active male. In 12 of the pairs, the female that gave birth in the presence of a lactating-pregnant partner either did not mate, mated but failed to implant, resorbed her fetuses or delivered non-viable young. Several mechanisms that might underlie this evident suppression of fertility are discussed.