What measures improve the conception rate of cattle frozen semen improvement
?Transport and storage of frozen semen
1. The semen must come from a legitimate breeding supply unit, and excellent breeds suitable for local growth and development and market demand should be selected. The quality of frozen semen should meet the provisions of national standards.
2. When moving the liquid nitrogen container, hold its handle, lift and place it gently, prevent collisions and tilting, and protect the vacuum extraction valve. During transport, lay down a thick soft pad, secure it appropriately, and according to transport conditions pack it in a thick cardboard box or wooden box, firmly tied to the vehicle to avoid bumping and impact.
3. During the storage of frozen semen, the condition of the liquid nitrogen container should be checked frequently. If abnormal conditions such as a significant increase in liquid nitrogen consumption or frost on the outside of the container are found, it should be replaced immediately; when the liquid nitrogen capacity is less than 1/2, replenish it in time. The minimum liquid nitrogen amount must not be lower than 1/3 of the container's total volume. The remaining liquid nitrogen amount can be estimated by the weighing method, or by inserting a thin wooden stick to the bottom of the container, taking it out after 10 seconds, and estimating based on the measured length of the frost line.
4. When taking out or placing frozen semen, the bucket or packaging containing the frozen semen can only be raised to the base of the container neck, and must not be raised outside the neck opening. Movements should be quick. If taking out or placing is not completed within 10 seconds, it should be put back into the liquid nitrogen to soak briefly before continuing; when stored frozen semen needs to be transferred to another container, the time spent outside the container must not exceed 5 seconds. If a longer time is needed, it should be handled in a container filled with liquid nitrogen.
Estrus identification and timely insemination
Estrus identification
1. External manifestations. This mainly judges the degree of estrus and determines the breeding time based on the external manifestations of the cow. When a cow is in estrus, it shows restlessness, loud mooing, licking and rubbing each other, placing its neck on another cow's back, performing some affectionate behaviors, sniffing the vulva of other cows, swelling of the labia, and discharge of transparent strip-like mucus from the vagina.
2. Vaginal examination. This method cannot accurately determine the ovulation time of the cow and is only used as an auxiliary method. Early stage: the vaginal mucosa is pink, lusterless, with a small amount of mucus, and the external opening of the cervix is slightly open; middle stage: mucus flows out in a glass-rod shape, the labia are loose and swollen, the vaginal mucosa is flushed red, with strong luster and a smooth moist feeling, the mucus often contains blood streaks, the external opening of the cervix is swollen, loose, and open, the cervical opening is slightly open, and the labia are swollen; late stage: the mucosal color becomes lighter, the mucus is viscous and turbid, and the cervical opening contracts and becomes less swollen and wrinkled.
3. Rectal examination. Rectal examination is a relatively accurate and commonly used method for judging cow estrus. In the early stage of estrus, the follicle begins to develop and increase in volume. When touched, only a softened point the size of a bean grain can be felt; in the middle stage, the follicle rapidly enlarges, the ovarian surface is smooth, the follicular wall becomes thinner, with a slight sense of fluctuation, lasting about 10 hours to 12 hours; in the peak stage of estrus, the follicle volume no longer increases, the follicular wall becomes thin, with an obvious sense of fluctuation, and the cow's estrus symptoms gradually disappear from weak, at which time the conception rate of insemination is highest; in the late stage of estrus, the follicle ruptures, the follicular fluid is lost, forming a small depression. The corpus luteum begins to form 6 hours to 8 hours after ovulation and protrudes on the ovarian surface. At this time, the depression at the ovulation site can no longer be felt.
????Timely insemination
The timely insemination time for cows should be determined based on their external manifestations and follicular changes. Practice has proved that insemination at the late stage of estrus or near the late stage of estrus has the best effect. In order to improve the conception rate, in practical work it is recommended to inseminate 2 times within 1 estrous period, with an interval of 8 hours to 12 hours.
?Correctly master insemination techniques
Strict disinfection
The operating room should be kept clean, hygienic, ventilated, and well lit, with no dust on the floor. Prevent mosquitoes, flies, and mice from entering the room. Disinfect the room regularly with an ultraviolet lamp or 0.1% benzalkonium bromide solution; wet the insemination site with 0.1% benzalkonium bromide solution to prevent dust from flying. Before insemination, wash the cow's vulva and surrounding area with 0.2% potassium permanganate solution, then wipe dry with a dry towel; insemination instruments can be disinfected with high-pressure steam or 75% alcohol, then rinsed with physiological saline.
Insemination operation
It is necessary to achieve slow insertion, appropriate depth, gentle infusion, slow pushing, and prevent backflow of semen. Specific method: before inserting the hand into the rectum, wear gloves, apply lubricant or soapy water, keep the hand holding the insemination gun as dry as possible, form the left hand into a cone shape and insert it into the rectum, determine the position of the cervix, and gently grasp it. Then, wipe the vulva clean with a paper towel or cotton ball, insert the insemination gun upward at 45°, and gradually rotate it while advancing the insemination gun forward so that it becomes horizontal, which can avoid entering the urethra or bladder; continue moving the insemination gun forward, and when a sense of elasticity is felt, stretch the uterus forward so that the vaginal folds extend forward. If obvious friction is felt, it indicates that the cervical opening has been reached; grasp the cervix and, through coordination of both hands, make the insemination gun enter the cervical canal. Note that the cervix protrudes into the vagina, so it is necessary to move the insemination gun back a little, and hold the rear part of the cervix with the thumb and index finger. The base of the thumb and the little finger may close off the cervix so as to accurately find the cervical opening and smoothly enter the cervical canal; the canal passing through the cervix is not smooth. If the insemination gun is obstructed by a cervical ring, gently move the insemination gun back a little, coordinate both hands, and insert again. Do not force the insemination gun through the cervix. For older cows, sometimes the uterus has drooped into the abdominal cavity, and it must be lifted up so that it forms a straight line with the insemination gun. For young cows that have not given birth, the insemination gun may not be able to pass completely through the cervix. When the insemination gun reaches the deep part of the cervix or the uterine body, insemination can be carried out.
?Strengthen the feeding and management of the frozen semen improvement cattle herd
Feed cows scientifically so that they maintain moderate body condition. Before estrus arrives, increase light exposure, strengthen exercise, and increase the supply of protein feed, which can ensure vigorous reproductive function, promote egg production and release, and prevent embryonic death; strengthen the feeding and management of cows in late gestation and after calving, and increase the energy supply in the feed, which can improve the conception rate during the postpartum estrous period. At the same time, strengthening feeding and management is of great significance for identifying whether conception has occurred, preventing missed mating, and preventing miscarriage.
?Do a good job of early pregnancy examination to reduce miscarriage
After cows are mated, pregnancy examination work should be done promptly to prevent cows from being non-pregnant, to continue mating non-pregnant cows in time, and to strengthen feeding and management for pregnant cows and do a good job of protecting the pregnancy. The general manifestations after a cow becomes pregnant are: cessation of estrus, gentle temperament, increased appetite, improved body condition, glossy coat, and cautious and steady movement. After 2 months, rectal examination shows that the two uterine horns begin to be asymmetrical. The pregnant horn is about two times larger than the non-pregnant horn, the base wall of the pregnant horn is soft, and when touched there is fluid movement and no contraction. The ovary is soft and smooth in texture, and the uterine artery begins to pulsate; the base wall of the non-pregnant horn is hard, and when touched there is no fluid movement. The ovary is hard in texture, and the uterine artery has no pulsation.