Mastering the technology of cow breeding is very important
1. Breeding technique of cow
1, sexual maturity
When the calves develop to a certain point, the reproductive organs are mature and have the ability of reproduction. This is called sexual maturation. The age of sexual maturity varies with breed, feeding management, climate, nutritional status and growth and development. Under normal circumstances, cows 8 to 12 month old achieve sexual maturity. In general, the first mating age of cows is 18-24 months old, and the weight of cows should reach 65-70% of adult weight. Early mating will affect their own development. But it should not be too late, otherwise it will reduce the calf number of cows throughout their lives, which is harmful to production.
2. The estrous cycle (also called the sexual cycle)
Before the onset of sexual maturation and aging, the cows were in a cycle of estrus without pregnancy. The interval from the onset of this estrus to the start of the next estrus is called estrous cycle. The average estrous cycle of cows is 21 days, ranging from 18 to 24 days.
When the cow is oestrus, a series of physiological changes have occurred inside and outside of the body. According to these changes, the estrus can be divided into four periods: first, the prophase of the estrus, at this time the cow's reproductive gland activity is strengthened, the secretion is increased, but there is no mucus discharge in the vagina, and there is no sexual desire. The two is the oestrus period, during which cows show intense sexual excitement, the genital tract is obviously congested, the labia swollen, the cervical mouth opens, the gland activity increases, and the mucus is discharged from the vagina. If the egg is fertilized, that is, after the cow has been pregnant, the estrous cycle stops until the estrous cycle appears again after childbirth. If the egg is not fertilized, it turns into the anaphase of the oestrus. Three is the luteal formation in the ovary after ovulation, and the estrus disappeared and restored to its original state. Four is the love period, also called the period. From the time of the last oestrus to the beginning of the next oestrus, the sex organs were not changed, the sexual activity was in a relative state of rest.
3. The duration of estrus
The period from the onset of estrus to the end of external oestrus is called the duration of estrus. Oestrus duration of cows varies with age, nutritional status and seasonal changes, generally 18 hours, ranging from 6 to 36 hours. The ovulation time of cows is 12 to 15 hours after the end of estrus. These basic knowledge is the key to choosing the time of insemination. The mating personnel should be informed in time to ensure the successful mating.
4. Oestrus identification of cows
Oestrus identification is the use of comprehensive technology to determine the estrous stage of the cow and determine the best mating time, so that artificial insemination can be carried out in time to maximize the goal of the rate of breeding.
There are many methods of oestrus identification, such as external observation, trial, vaginal examination, rectal examination and bionics. In my opinion, in the absence of advanced equipment, the most important thing is the external observation method.
Cows are uneasy when they are in oestrus. They are sensitive to changes in the environment, look around, lose appetite or eat, sometimes call, chase the bull, climb other cattle, and accept other cows. When other cows climb, the cow has two hind legs opened, arched back, and frequent urination. The vulva is swollen and the mucus is flowing out of the vagina; the amount of mucus is more and more transparent during the orgasm. With the extension of the estrus time, the amount of mucus gradually decreases, thicker and cloudy. At this time the cow lay down, the mucus stained on the tail, so that there was a lot of sediment on the tail. Sometimes there is a small amount of blood in mucus at the end of estrus, which is common in young cattle. A small number of cows shed a small amount of dark red liquid from the vulva after estrus, known as "cow menstruation". A few cattle have no obvious external changes in oestrus, that is, the oestrus symptoms are not obvious, known as "dark oestrus" or "quiet oestrus". There are several ways to identify the dark oestrus: To observe the mother cattle carefully, because the oestrus cows always have to appear swollen, only the swelling degree of each cow is different or more or less the flow of mucus; it can be used to predict the cow's oestrus according to the reproduction record, and the cow menstruation can also be used to trace the cows in the dark. Castrated bulls look for cows with dark estrus to prevent mismatch. In addition, a few cows have estrus after pregnancy, which is called "false estrus". 3% to 5% of the cows in the cattle show false oestrus. Attention should be paid to identification and mismatch should not result in miscarriage. Differentiation methods: The general bovine wig estrus, oestrus symptoms are not strong, short duration, vaginal swelling is not obvious, mucus volume is not much or no mucus. The cow's vulva is swollen, there are mucus, crawling across other cattle and other cows to climb, which is the obvious sign of the cow's oestrus; the cow's vulva swelling disappeared and the wrinkles came out, which was the sign of the end of the external performance of the oestrus. The difference between the two is very obvious. Technicians should go deep into the herd twice a day in the morning and evening to observe the cows, and closely cooperate with the breeders for estrus identification.
5, insemination time
The ovulation time of cows is 12 to 15 hours after the end of external performance. After ovulation in the oviduct to maintain fertilization time for 8-12 hours, so the time of insemination is arranged before ovulation 6-8 hours, the highest rate of conception. However, ovulation time is not easy to accurately grasp, and according to the estrus time to grasp the time of insemination is easier, to the late estrus better insemination.
Two. Variety improvement and establishment of hybrid pedigree
The establishment of hybrid genealogy is to avoid inbreeding, resulting in lack of good characters.