Physiology of Canine Reproduction. How dog reproduce.

The sexual cycle in Dogs:It includes the time of heat, but also the times of resting.
The female Dog: Female dogs have two periods of heat a year, every six months, which last about 2-3 weeks each. Their first heat appears between 6 and 15 months after birth, and the dog can be fertilized since this time. The appearance of heat is produced later on in the larger breeds, since these have a longer growth. The female dog has spontaneous ovulation. This means that ovulation is independent from being mounted. This occurs every 6 months. A late or anticipated heat is not strange. The duration of this cycle varies from an animal to another and also depends on the breed, but it is usually between 150 and 300 days. This cycle has four phases: the proestro, and the estro, that constitute the period of heat, and the diestro and anestro which are the phases of sexual resting. The behavior, physiology and anatomy of the animal go through different changes with each phase of heat.

The Proestro: With a duration of 7 to 10 days, it indicated the beginning of heat. We can observe the first loss of blood and an increased visibility of the vulva. In this phase the male feels attracted to the female, but she rejects being mounted.

The Estro: This phase comes after the proestro and lasts from 5 to 10 days. The loss of blood decreases and then completely stops. The male is accepted. Ovulation takes place during this period; it happens generally 2 to 3 days after the male has been accepted. This is a very important factor because it means that the ideal moment for reproduction is not when the female accepts to be mounted.

The Diestro: This stage lasts from 110 to 140 days. The female is in gestation, or is resting sexually if she has not been fertilized.

The Anestro: This phase comes after the new heat; it has different lengths, having in mind that the dog is in heat two times a year.

The Male: The male does not have a precise cycle; it is in heat when the female is present.
In the male dog that has matured recently, the sperms are not numerous and can sometimes present anomalies. Their fertility is not at its maximum and it is better to wait until it is about 10 or 15 months old before its first intercourse. During these cycles, many hormones are secreted. We will not revise all of these molecules, but it is precise to know the most important hormones to understand the regulation of the cycle and its disfunction.

The hormonal regulation: A hormone is a substance secreted by a gland that acts on an organ. The sexual cycle depends completely in sexual hormones, which are different in the male and female.

In the female
Estrogens:
These hormones are secreted by the ovaries during heat. Their function is to stimulate the hypothalamus, which will secrete other hormones that will provoke ovulation.

Progesterone: It is secreted by the yellow body, in the moment of ovulation. It is indispensable for gestation.

The Gonadotropines: These are secreted by the hypophysis gland. These are two: the FSH, that stimulated the growth of the follicles and is used for therapeutic ends, and the LH that unleashed ovulation.

The Oxiticine: It is secreted by the same gland as the FSH; it permits the dilation of the tissue during birth. It is also used to provoke labor.

The Prolactine: Also secreted by the same gland, it stimulates the secretion of milk after giving birth. In the maledog

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