The reproductive cycle

During the early stages of the embryo's life, the genital system of both sexes develops in exactly the same way. Sexual differentiation occurs in cattle at an earlier stage than in almost any other mammal, starting when the foetus is about 40 days old. The cortical sexual cords contain the primordial gonocytes from which the cells develop that eventually produce the ovum. By birth, all the oocytes will have formed and no new ones will develop.  View the follicles inside the ovarian structure . 

With the exception of the entrance orifice or vulvaExternal genitalia in female placental mammals., the female's genital organs are located in the pelvic-abdominal cavity. The genital organs do not simply produce gametes and sexual hormones; they provide a location for fertilisationUnion of a male gamete (sperm) with a female gamete (ovum) to give an egg, or zygote. and are responsible for pregnancy, parturition and lactation. Review the anatomy of the reproductive system .

The cow is a continual-type, polyoestral species with an average cycle length of 21/22 days for previously bred cows and 20 days for heifers. Sexual activity starts at pubertyTransition between youth and adulthood, characterized by the development of sexual characteristics, accelerated linear growth and acquisition of reproductive functions., when the animal has reached 40 to 45% of its adult weight, and then follows a cyclic pattern, characterised by the periodic onset of oestrusAlso known as heat, is the physiological and behavioral phenomena which precedes and accompanies ovulation in female mammals.. OestrusAlso known as heat, is the physiological and behavioral phenomena which precedes and accompanies ovulation in female mammals., when the animal is "on heatAlso “oestrus”. Physiological and behavioural phenomena that precedes and accompanies ovulation in female mammals.", is the time when the male is accepted and mounting occurs. This period coincides with the presence of a mature Graafian follicleSmall secretory or excretory cavity. Ovarian follicles grow until ovulation or female gamete emission. in the ovaryFemale reproductive glands, located symmetrical on either side of the uterus, which produce the female gametes., which is later released by ovulationExpulsion of an ovum from the ovary in female animals.. OestrusAlso known as heat, is the physiological and behavioral phenomena which precedes and accompanies ovulation in female mammals. lasts from 6 to 30 hours and is characterised by visible signs: excitation, anxiety, bellowing, inciting mounting behaviour from other animals and passive acceptation of being mounted by a bull or another cow, in addition to increased vaginal mucus. OvulationExpulsion of an ovum from the ovary in female animals. occurs 6 to 14 hours after the end of oestrusAlso known as heat, is the physiological and behavioral phenomena which precedes and accompanies ovulation in female mammals. and is followed by the formation of the corpus luteumOrganelle formed after ovulation of a dominant follicle. Its thick wall is formed from progesterone-secreting cells. It is the sign of the cyclical activity being maintained in the event of pregnancy. and the start of a period when the uterusGenital organ of female mammals, located between the fallopian tubes and the vagina, which hosts the fertilized egg until its full development takes place and it is expelled at the end of gestation. becomes gravid, corresponding to the time when the luteal function is active. Find out more about the oestrus cycle .