Biomedical subjects

D V Klotchkov

Publications and source records attributed to D V Klotchkov.

3 recordsLinked to original sources

PubMed2003

Effects of hCG on folliculogenesis and fecundity in mink (Mustela vision Schreb).

The endogenous hormonal response obtained after reproductive organs are challenged by exogenous hormones is increasingly being used to predict presence of functional reserves and to apply this information to improve efficiency of managed breeding programs. With that in mind, the aim of the present study was to investigate the effect of a single treatment with hCG on folliculogenesis and fertility in standard 7-month-old mink females. The extent of stimulation following treatment was determined by examining patterns of vaginal smears. Characteristics of each cycle stage were: estrus, preponderance of cornified epithelial cells; proestrus, polygonal, elongate epithelial cells; anestrus, parabasal, intermediate and leucocyte cells. Smears exhibiting a mixed population of cells were categorized as being in transition between adjacent stages anestrus-proestrus or proestrus-estrus. The initial evaluations were done on Day 6 after hCG treatment. Histomorphometric examination of ovaries and uteri was done during seasonal anestrus (November) and in the breeding season (March). Vaginal cytology patterns were correlated with changes in folliculogenesis. A mean of 1.3 mature (Graafian) follicles were counted during estrus, while the mean number seen during anestrus, anestrus-proestrus and proestrus, were 0.4, 0.3 and 1.0, respectively. During the breeding season, in females that were not treated, the numbers of growing follicles decreased and maturing follicles increased, whereas females that came in estrus after treatment with hCG in November had increased numbers of both growing and maturing follicles. Fertility after breeding in hCG-treated females was increased by 9.2% (P<0.05) as compared to untreated females. Females showing the highest fertility rise (27%) were predominantly in the group that showed estrus after hCG treatment. We conclude that monitoring the response of the mink reproductive system to hCG stimulation in November may be a useful tool for identifying females of high fertility in the spring.

Animals↗

PubMed1998

Folliculogenesis, onset of puberty and fecundity of mink (Mustela vision Schreb) selectively bred for docility or aggressiveness.

It has been suggested that selective breeding of animals for docile behavior is correlated with early onset of puberty and improved fertility. We wished to test the hypothesis that mink bred for docility would show earlier onset of puberty and greater fecundity than mink bred for aggressiveness. We used farm-raised, 7-mo-old mink females that had been selectively bred for 7 to 10 generations on the basis of behavior towards humans. Onset of puberty was estimated once (between 15 and 20 December) by vaginal smears and was said to start wtih preponderance of cornified epithelial cells in the cytological specimen. Fecundity was measured by litter size and rate of folliculogenesis, with and without hCG stimulation, by histomorphometric examination of ovaries and uteri. A total of 43/100 (43%) docile females achieved proestrus and estrus as compared to 16/136 (12%) of the aggressive ones. Overall pregnancy rate, survival to 5 d after whelping and litter size did not differ between the docile and aggressive females. Docile females showed significantly higher numbers (P < 0.05 and < 0.001) of growing, maturing and atretic follicles than the aggressive ones, however the latter showed a highly significant (P < 0.001) folliculogenic response to hCG. The response of the ovary of aggressive females to hCG is particularly dramatic because in most aggressive females the ovaries contained none or only few follicles of any kind. The inhibition of folliculogenesis in aggressive mink is similar to that reported in Silverblue and Sapphire mink homozygous for the Stuart factor. The paradoxical response to hCG may be an indication that selective breeding for aggression may be correlated with the disturbance at the early stages of folliculogenesis which creates a deficiency of follicles that are sensitive to LH-type stimulation.

Aggression↗

PubMed1995

Gonadal function in mink under artificial photoperiods.

Exposure of juvenile minks to artificial light conditions imitating early autumn (additional illumination from 20 June to 20 July followed by 8 h daylight from 21 July to 10 October--photoperiod I; 8 h daylight from 21 July to 10 October--photoperiod II) induced the prolonged modification of sex steroid concentrations. The increase in plasma testosterone concentrations during the prepubertal period was followed by a decrease before and during the mating period in experimental males. The concentration of oestradiol in plasma increased just before the start of the mating period (January and February) in females under photoperiod I, and these hormonal changes were accompanied by an increase in fertility. The conditions of photoperiod II (involving fewer hours of daylight) had less effect on the sex steroid concentration in the blood of females, and fertility was not changed. The response of gonads to hCG injection at the beginning of puberty (November) was higher in males exposed to photoperiod I conditions and in females exposed to both photoperiods than in control animals.

Animals↗