Читать книгу The Complete Book of Dog Breeding - Dan Rice - Страница 14

The first estrous cycle phase is called proestrus. Its outward, physical signs are obvious. All the female’s reproductive tissues thicken, her vulva swells, and visible genitalia becomes reddened. Bloody vaginal discharges are produced, and the bitch usually spends an extraordinary amount of time licking her external genitalia. She may act nervous and her appetite is reduced. In early proestrus, some bitches are snappy toward other animals.

As the days of proestrus count down, she tries to escape from confinement, seeking a mate. The bloody discharge attracts males from near and far. If housed with intact males, they will begin paying court to the bitches. If females are allowed outside, male dog visitors should be expected.

Prior to puberty, intact bitches’ internal reproductive organs (except their ovaries) are quite undeveloped. The actual weight and dimensions of prepuberal (before the first heat) uteruses are significantly smaller than those of sexually mature animals. As puberty is reached and proestrus begins, the uterus enlarges in response to hormones secreted from the ovaries. Although that enlargement is unapparent to the owner, it can sometimes be palpated by veterinarians with practiced fingers, and it is easily demonstrated by ultrasound imaging.

Proestrus lasts from two to 27 days, more typically seven to ten days. The average length of proestrus is generally accepted to be nine days.

During this phase, estrogen hormone levels rise gradually in the bloodstream, and levels of the progesterone hormone remain relatively low.

This Cavalier King Charles Spaniel has a rather large litter of six fine puppies.

Another hormone called follicle stimulating hormone (FSH) originates from the pituitary gland. For two or three weeks prior to the onset of proestrus, serum levels of FSFI rise. Its effect is to stimulate production of follicles within the ovaries. These follicles contain microscopic eggs called ova.