When heifers reach puberty (first ovulation) or after postpartum period of the absence of a cycle in cows, the estrous cycle begins. Thanks to sexual cycle, a heifer or a cow can become pregnant every 21 days. During each sexual cycle, follicles develop in waves, which is controlled by changes in concentrations hormones. In addition, the corpus luteum (CL) develops after follicle ovulation. Bye CL present, it prevents the ovulation of others follicles. The duration of each estrus cycle is measured by the number of days between each standing heat.
Periodic changes in the reproductive system of the uterus and their ability to fertilize is called the sexual cycle.
Sexual cycles in heifers regularly begin to appear from 8-9 months of age. However, during this period, the formed follicles often resolve, ovulation does not occur, and heifers remain unfertilized.
The sexual cycle in cows and heifers is repeated after 21 days with possible deviations of 10-20 days. It ends with ovulation, i.e. release of the egg from the ovary into the uterus.
Outwardly, this is expressed by estrus, which lasts for 3-4 days in cows. And hunting, which becomes most pronounced a day after the onset of estrus.
Double insemination at the end of the hunt and 10-12 hours after the first insemination guarantees fruitful insemination.
In most cases, estrus and hunting are easy to determine by external signs. Viscous mucus is released from the genital slit, milk production decreases, physical activity increases, the search for a sexual partner, courtship, jumping up, a reflex of immobility is formed, etc. From the practice of highly productive dairy farms, it is known that insemination during the first heat after calving does not always lead to fertilization, because. the body of the cow is still weakened.
The optimal period of fruitful insemination is the second hunt, 40-45 days after calving, in this case, the fertility from the first insemination is 65-70%.
However, any delay in insemination beyond this period is highly disadvantageous. Delayed insemination is often associated with poor performance of the inseminator.
It is known that 30-40% of cows come to hunt at night, this excludes their choice, because. the hunting period, when there are external signs, ranges from 30 minutes to 12 hours, and usually less than 6 hours. Under optimal conditions of keeping, with full feeding, sexual reflexes are intensely manifested in 75-80% of cows.
With a single inspection, the technician can identify no more than 60% of the cows that are in heat and are subject to insemination. Therefore, control over the physiological state, keeping records, 3-4-fold examination during the day of the entire herd are the basis of the work of each inseminator. It is economically extremely important to fertilize a cow in the first 80-85 days after calving. When carrying out fertilization, after 2-3 cycles of insemination, the cow is examined by a veterinarian, and the sperm of the bulls is carefully checked. Its mobility, resistance and other qualities. To stimulate the sexual cycle in cows, the following are used: prostaglidins (estrofan, aniprost, estufalan, dinaprost, prostin, etc.), gonadotropins (FSH, LH, FFA folliculin, etc.), as well as progestogens, estrogens, oxytocin, corticosteroids. The use of hormonal drugs is carried out on the recommendation of a veterinarian and under his supervision. In order to increase fertility, the uterus and ovaries are also massaged with preliminary irrigation of the vagina and cervix with a warm 1% solution of table salt.
The biological laws of reproduction inevitably manifest themselves in all systems of production of livestock products. However, the organization and execution of this technological operation differ significantly when keeping animals in a private backyard, in a farm, and in large industrial complexes.
Free mating of cows that are in personal use most often takes place in a common herd, where for every 50 queens there is one bull - a producer.
In winter, when the cattle is not grazing, manual mating of cows is used on the walking area. The farm herd structure typically contains a sire for manual mating of cows.
In order to increase economic efficiency and improve the quality of offspring, it is necessary to develop artificial insemination of animals, both on a personal farmstead and on farms.
On large farms there are specially built artificial insemination stations, there is a staff of artificial insemination technicians.
The duties of the staff of the point include monitoring the cyclicity of the sexual activity of cows, keeping records on the forms 10-mol and 12-40 (card and log of the launch of calving and insemination), identifying cows and heifers in the hunt, inseminating them and determining pregnancy together with the veterinarian of the farm. On the 50-60th day after the last insemination, a rectal pregnancy test is performed. For early diagnosis, 10-15 days after insemination, a hormonal method is used. The level of progesterone in the milk of pregnant cows is much higher.
