ARTIFICIAL INSEMINATION

Transcription

1 ARTIFICIAL INSEMINATION Artificial insemination is the deposition of male reproductive cells (spermatozoa) in the female reproductive tract by mechanical means rather than by natural mating. The success of the insemination depends mainly upon i) the inherent fertility of the sperm, (ii) proper handling of the semen prior to insemination, (iii) insemination at the right time during oestrus, and (iv) proper semen deposition. Advantages of A. I. over Natural Breeding 1. The main advantage of A.I. is that it increases the usefulness of superior sire to an extraordinary degree. It makes available sires of inheritance for milk and butter fat production to all dairymen within a limited area. Previously only a few could get the advantage of good bulls. 2. The services of superior sires are greatly extended. By natural services, a bull can be bred to 50 to 60 cows per year; on the contrary New York Artificial Breeders Co-operative have sired 10,000 in one year by one bull. It would have taken about 200 years to accomplish this by natural service of that bull. 3. The breeder does not need to maintain a herd sire and thus can avoid the botheration accompanied with the management of a bull. It helps to regulate the breeding programme and the space between successive calving without unnecessarily prolonging the dry period. 4. The dairyman does not have the problem of searching and purchasing a new herd sire every two years to avoid inbreeding. 5. The technique of A.I. can be made use of in cross breeding for hybrid vigour by quickly transporting the semen by air to different continents. 6. The intensity of the spread of genital diseases is lessened if the specially trained persons conduct A. I. under complete sanitary conditions. 7. Overcomes the difficulty of size and weight. 8. Increases rate of conception, 9. Outstanding animals located apart can be mated. 10. Helps in better record keeping. 11. Old heavy and injured sires can be used with advantages. Limitations of A.I. 1. Requires well-trained operations and special equipments. 2. Requires more time than the natural services. 3. Necessitates the knowledge of structure and function of Prepared by Tshewang Dorji 1

2 reproduction, on the part of the operator. 4. Improper cleaning of the instruments and unsanitary conditions may lead to lower fertility. 5. Market for the bulls is reduced while that for the superior germ plasm is increased. 6. Selection of the sire should be very rigid in all respect. Detection of Oestrus and Time of Insemination in Cow Maximum fertility will be achieved by having highly fertile sperm present in the oviducts when ovulation occurs. Since the life of the ovum is relatively short. about two hours, the sperm should reach sufficiently ahead of ovulation to effect proper fertilisation Thus insemination should precede ovulation. Ovulation time is difficult to determine routinely, so inseminations should be timed from the onset of oestrus. Checks for oestrus must be done carefully and regularly. Usually cows come in oestrus condition after every 21 days if non-pregnant. In case one fails to detect oestrus for the first time, he may be very careful on and from 19th day to 21st day after the failure to detect oestrus on the first time. In the cows, oestrus is indicated when the female stands to be mounted by another animal. Cows first seen in oestrus, in the morning should be inseminated the afternoon of the same day; those first observed in oestrus in the afternoon should be inseminated the next morning. The stimulus of insemination may reduce- the interval from the end of oestrus to ovulation. Site of semen deposition. In the cow the best fertility can be obtained with the recto-vaginal technique. A gloved hand is inserted into the rectum of the cow and used to pick up the cervix and thus the rectal wall. An inseminating tube is then inserted into the vagina and is guided into or through the cervix by means of the gloved hand in the rectum. Sufficient practice is necessary before an individual becomes proficient at this technique. Some kind of non-irritating lubricant should be used on the gloved hand. Applying some of the lubricant to the anal region prior to the insertion of the cupped hand through the anal musculature is advisable. Insertion of the inseminating tube into the vagina should be started with the tip pointed upward at an angle of degrees. This avoids the possibility of having the tip enter the blind pouch or urethral opening. The gloved hand in the rectum should be used to follow the tip of the inseminating tube as it is gently pushed into the vagina, for the tube will serve as a guide in locating the cervix. Deposition of the semen through the cervix and in the anterior portion of the cervix is recommended. Prepared by Tshewang Dorji 2

3 THE EQUIPMENT YOU WILL USE: Storage container Aluminium or stainless steel vacuum vessel used to hold semen and Liquid Nitrogen Canister: Removable cylinder with mesh-bottom to hold semen in the containers. Has a long hooked handle to permit identification and access from the mouth of the container. Goblet: Plastic cylinder with liquid-proof bottom that fits into but is half the height of the normal canister. This allows two layers of semen storage. Straws to be kept for longer than a few weeks should be held on the bottom layer. Manufacturer s end of straw: During manufacture the straw has a double wad and powder plug fitted. This eventually seals one end of the straw (when the powder is moistened during filling). It also acts as the piston that pushes the semen out of the straw when the inseminator depresses the plunger of the gun. After filling in the processing laboratory, the powder seals the straw. The powder may be of varying colours and is generally from 3 to 8 mm long. The inseminator cuts off the seal during the loading of the insemination gun. INSEMINATION TECHNIQUES: Insemination must be done properly and this is essential for any A.I. operation. Techniques: 1. Speculum method 2. Recto-vaginal method The most commonly used technique throughout the world is the Recto-vaginal technique. The speculum method was found in favour earlier because little experience was needed but there were certain Straws: Each straw contains one cow dose. The volume of a straw is 0.5 cc for the medium-straw and 0.25 cc for the mini-straw. Prepared by Tshewang Dorji 3

4 serious drawbacks. One of these was the need for cleaning and sterilizing the speculum after each insemination. The conception rates are not as good as they are with the recto-vaginal technique. The Recto-vaginal technique on the other hand requires considerable practice before proficiency is reached. Careful approach and handling of the cow during insemination Proper recording of A.I. in the A.I. register Proper cleaning and handling of all materials and equipment Proper insemination techniques involve: Proper identification of the cow before insemination Interrogating the farmer in order to obtain a clear picture about the history of the cow. External examination of the cow to be inseminated Proper selection of the semen Application of correct thawing techniques there frozen semen is used Proper preparation of the insemination gun. 1. The History of Animal: Before starting with the actual insemination, the person presenting the cow should be asked about when the cow calved and whether any abnormal discharge or abnormal behaviour was noticed. Also get the information on heat observation by the owner. Cows should not be inseminated within 60 days after normal calving and not within 90 days in case of an abnormal calving or in case of abnormalities after calving. Animals that have shown abnormal discharge from the vulva in the three weeks period prior to present insemination should also be refused. 2. External Examination: The next thing to do is the external examination of the animal: Hygienic handling of insemination gun and animal Thorough rectal examination of vagina, cervix and uterus before actual insemination Proper introduction of the gun into the cervix The tail, the vulva and adjacent parts should be carefully checked for the presence of mucous or purulent discharge Are there signs of standing heat on the rump or the tail head - a cow that has been mounted is likely to show mud or scars on these areas Deposition of the semen at the right spot in the genital tract of the cow Open the lips of the vulva with the fingers and check the clitoris and the mucous membranes; in case of Prepared by Tshewang Dorji 4

5 abnormal discharge, flocks of pus are likely to be detected on the clitoris. Animals that show abnormalities in external examination should be refused for insemination and necessary treatment should be carried out. 3. Rectal Palpation of Cow: One hand is gloved and the glove is lubricated with a special non-irritating lubricant Make the gloved hand into cone shape and insert in the rectum with gentle movement If necessary, remove the dung from the rectum by gently back racking Carefully palpate the cervix and the two uterine horns; if the cervix is soft and pliable and if the uterine horns are rigid and contract on palpation (Tonicity), the cow is definitely in heat However, if the cervix is hard and rigid and the uterine horns soft and flabby it is unlikely that the animal is in heat The uterine horn should be carefully checked for endometritis, pregnancy or abnormalities Cows with abnormalities or without obvious heat signs should never be inseminated Step I - Thawing of Straw: Warm water at 32 to 38 degrees Centigrade. It is essential to use a thermometer. Dipping a finger into the water is not reliable. Thawing water above 40 degrees Centigrade may kill the spermatozoa Remove the neck plug from the storage container Select the canister containing the semen required. Lift the canister hook and swing canister to the centre position Lift the canister to the top of the frost line in the neck of the container (50 mm below the top of the neck). Do not bring the canister up to the top of the neck. The goblet may be raised to the top of the canister by using forceps. The goblet should be always full of liquid nitrogen. Pick up a straw and return the goblet to the bottom of the canister and return the canister to the bottom of the container in the correct position Shake the straw and place it in the thawing water for 30 seconds Replace the neck plug in the container Avoid touching the ovaries during rectal palpation; palpation of the ovaries of cows in heat can provide rupture of the follicle and then the cow will no longer be able to conceive Thawed straw should be used within 20 minutes and once thawed, a straw should not be frozen Remove straw from water and gently dry with tissue paper or clean towel Prepared by Tshewang Dorji 5

6 Make final identification of straw Step III - Inseminating the Cow: Step II - Loading the Gun: Pull the plunger of the gun 10 cm out of the gun Push the manufacturer s end (double wad end) of the straw into the insemination gun as far as it goes. This should leave the straw protrude about 3.5 cm Hold the loaded gun vertical at eyelevel and with clean sharp scissors make a horizontal cut 1 cm off the tip of straw to remove the laboratory seal. The cut must be at right angle to the straw to ensure a perfect seal between the straw and the outer sheath Remove a sheath from a protective container and place it over the barrel of the gun. The function of the sheath is to prevent contamination of the gun and to hold the straw in place during expulsion of the semen. Fit the sheath over the gun and through the O ring. The sheath is slit at its bottom to fit over the enlarged portion of the A.I. gun. Push sheath firmly onto the enlarged portion of the gun using a sensible amount of force and push the plastic ring tightly over the sheath and the A.I. gun. Put a disposable glove on the left hand and wet the gloved hand and are by dipping into a bucket of clean water, then allowing to run back down the are. Apply a small quantity of liquid soap or lubricant Carry the loaded insemination gun in the mouth. Be sure the end of the gun does not become contaminated by contact with projecting objects or walls. Also take care not to bump the plunger on a wall or post while inserting the hand into the rectum of the cow Make the cow aware of your approach Protect the hand from contamination with a piece of paper, then take a firm hold of the cow s tail and lift it aside Insert the hand into the rectum and remove the dung by back racking Thoroughly clean the vulva of all soap, dung and dirt by wiping with a clean tissue paper Grasp the cervix and pull it slightly towards you so that vulval lips open. Then guide the gun through the vulva into the vagina. It may be necessary to push the cervix forward to straighten any vaginal folds Slowly and firmly move the piston up the gun until the movement of the semen at the tip is seen. Be careful not to expel the semen. You are now ready to proceed with the actual insemination When the gun reaches the external os of the cervix, hold the cervix firmly then try to thread the cervix over the gun. It will probably be necessary to move the cervix slightly in order to find the opening. Never do more with the cervix than is necessary to get the job done. Use minimum strength and Prepared by Tshewang Dorji 6

7 minimum of movements - all smooth and gentle. Make all movements purposeful. Try not to fumble or do anything without specific reason. In case of first insemination the semen should be deposited just in front it the internal os or in the mix cervix. The gun should not enter the uterus as this can cause serious injury to the uterine wall. In case of repeat insemination there is the possibility that a cow is actually pregnant. Therefore, it is recommended to deposit the semen at the external of and not to pass the cervix completely Deposit the semen by depressing the plunger slowly on third of the dose in the internal os and remaining two thirds in the mid cervix Pause before withdrawal to allow the semen to get away from the gun, then slowly withdraw the gun from the cervix because a rapid withdrawal can suck the semen back through the cervix and into the vagina Slowly withdraw the hand from the rectum of the cow Remove the soiled sheath from the gun after loosening the O ring. Do not allow the ring to contact the soiled part of the sheath. Slide the sheath from under the lock ring and remove it from the gun. The empty straw should come out with the sheath Dispose of the straw, sheath and dirty glove in a waste bin. Do not leave them lying around Reasonable care should prevent the unprotected parts of the gun from being contaminated. If these parts become soiled with dung or mucus the gun should be put aside until it can be thoroughly cleaned After completing all inseminations the following cleaning procedure should be carried out. Dispose of used sheaths, paper and plastic gloves, leave the soiled equipment behind Place any contaminated guns aside for through cleaning before use Wash hands particularly the non-gloved hand Keep your A.I. kit clean and tidy at all times and wash it thoroughly at regular intervals. Guns should be washed and rinsed at least once a week. After insemination, fill in the A.I. register provided to each A.I. Centre. Prepared by Tshewang Dorji 7