Measures to improve the conception rate of frozen bovine semen

? Transportation and Preservation of Frozen Semen

1. Semen should come from regular seed supply units, select fine varieties suitable for local growth and market demand, and frozen semen quality should meet national standards.

2. When moving the liquid nitrogen tank, hold the handle gently, prevent collision and tilt, and protect the vacuum evacuation valve. During transportation, thick cushions should be padded, properly fixed, packed in thick cartons or wooden cases according to transportation conditions, and firmly tied to the vehicle to avoid bumps and collisions.

3. During the period of frozen sperm preservation, the condition of liquid nitrogen tank should be checked frequently. If abnormal conditions such as significant increase in liquid nitrogen consumption or external frost in the container are found, it should be replaced immediately; when the liquid nitrogen capacity is less than 1/2, it should be supplemented in time. The minimum liquid nitrogen amount should not be lower than 1/3 of the full volume of the tank. The remaining amount of liquid nitrogen can be estimated by weighing method. It can also be inserted into the bottom of the tank with a thin stick. After 10 seconds, it can be estimated according to the measured frosting line length.

4. When taking and placing frozen semen, only lift the bucket or package for extracting and placing frozen semen to the base of the container neck, not to the neck opening, and move quickly. If the extraction and placement is not completed after 10 seconds, it should be put back into liquid nitrogen for soaking before continuing to take and place; when the frozen semen needs to be transferred to another container, the residence time outside the container shall not exceed 5 seconds. If it needs a long time, it should be processed in the container containing liquid nitrogen.

Estrus identification and timely insemination

estrous identification

1. External performance. It is mainly based on the external performance of cows to judge the degree of oestrus and determine the mating time. When cows are in heat, they are nervous, moo loudly, lick and rub each other, put their necks on the backs of other cows, do some intimate behavior, smell the vulva of other cows, have swollen labia, and have transparent mucus flowing out of the vagina.

2. Vaginal examination. This method cannot accurately determine the ovulation time of cows and is only used as an auxiliary method. Initial stage: vaginal mucosa pink, dull, with a small amount of mucus, cervical opening slightly developed; middle stage: mucus glass rod-like outflow, labia relaxation swelling, vaginal mucosa was damp red, with strong luster and smooth feeling, mucus often with blood, cervical opening swelling, relaxation, opening, uterine mouth slightly open, labia swelling; end stage: mucosa color pale, mucus viscous turbidity, uterine mouth contraction and swelling wrinkles.

3. Rectal examination. Rectal examination is an accurate and commonly used method for determining oestrus in cows. At the beginning of estrus, follicles begin to develop and increase in size. When touched, only the softening point of bean size can be felt. At the middle stage, follicles rapidly increase, the surface of ovary is smooth, the wall of follicle becomes thin, and there is a slight fluctuation feeling, which lasts for about 10 hours to 12 hours. At the peak of estrus, the follicle volume no longer increases, the wall of follicle becomes thin, and there is obvious fluctuation feeling. The estrus symptoms of cows gradually disappear from weak to weak. At this time, the fertilization rate is the highest. At the end of estrus, follicles rupture, foam loss, forming a small depression, 6 hours to 8 hours after ovulation began to form corpus luteum, and prominent on the surface of the ovary, at this time can not touch the depression of ovulation.

???? timely insemination

The timing of insemination in cows depends on their external appearance and follicular changes. Practice has proved that the best effect of sperm insemination is at or near the end of estrus. In order to improve the conception rate, it is suggested that insemination should be performed twice in one estrous period, with an interval of 8 ~12 hours.

? Correct Mastering of Insemination Technique

strict disinfection

The operation room should be kept clean, ventilated, well lit and dust-free on the ground. To prevent mosquitoes, flies and mice from entering the room, disinfect the room regularly with ultraviolet lamp or 0.1% benzalkonium chloride solution; wet the semen infusion site with 0.1% benzalkonium chloride solution to prevent dust from flying. Before insemination, wash the vulva and its surroundings with 0.2% potassium permanganate solution, and then dry them with dry towels; the insemination instruments can be disinfected with high pressure steam or 75% alcohol, and then washed with normal saline.

inseminating operation

To achieve slow insertion, appropriate depth, light infusion, slow strike, to prevent semen reflux. Specific methods: put on gloves, apply lubricant or soapy water before putting your hand into the rectum, keep your hand dry as much as possible, put your left hand into the rectum in a conical shape, determine the position of the cervix, and gently grasp it. Then, wipe the vulva clean with paper towel or cotton ball, insert the insemination gun upward at 45°, rotate gradually in the process of advancing the insemination gun to make it horizontal, so as to avoid entering the urethra or bladder; continue to make the insemination gun forward, when there is elasticity, stretch the uterus forward, make the vaginal folds stretch forward, feel obvious friction, indicating that it has reached the cervical orifice; Grasp the cervix, through the cooperation of both hands, so that the sperm delivery gun enters the cervical canal, note that the cervix is protruding from the vagina, so it is necessary to move the sperm delivery gun back a little, and hold the back of the cervix with the thumb and index finger, the root of the thumb and the little finger may close the cervix, so as to find the cervical orifice and smoothly enter the cervical canal; The passage through the cervix is not smooth. If the insemination gun is blocked by the cervical ring, gently move the insemination gun back a little, and then insert it with both hands. Do not force the insemination gun through the cervix. For older cows, sometimes the uterus has fallen into the abdominal cavity. It must be lifted to make it in line with the insemination gun. For young cows who have not given birth, the insemination gun may not pass completely through the cervix. When the insemination gun reaches the deep part of the cervix or the uterine body, You can inseminate.

? Strengthening the Feeding Management of Frozen Cattle

Scientific feeding of cows, keeping cows in medium body condition, increasing light before oestrus, strengthening exercise, increasing protein feed supply, ensuring vigorous reproductive function, promoting egg production and discharge, preventing embryo death; strengthening feeding management of cows in late pregnancy and postpartum, increasing energy supply in feed, can improve postpartum pregnancy rate. At the same time, strengthening feeding management is of great significance to identify whether pregnancy, prevent miscarriage and abortion.

? Do a good job of early pregnancy examination to reduce abortion

After cow breeding, pregnancy inspection should be done in time to prevent empty pregnancy, continue breeding in time for unpregnant cows, strengthen feeding management for pregnant cows, and do a good job in pregnancy protection. The general performance of cows after pregnancy is: stop estrus, temper docile, appetite, body condition better, hair smooth, cautious and stable action. After 2 months, rectal examination of both uterine horns began to be asymmetric, pregnant horn increased about twice than empty horn, pregnant horn base wall soft, touch there is liquid flow, no contraction, ovarian texture soft and smooth, uterine artery began to pulse; empty horn base wall hard, touch no liquid flow, ovarian texture hard, uterine artery no pulse.