Artificial insemination is the technique in which semen with living sperms is collected from the male and introduced into female reproductive tract at proper time with the help of instruments. This has been found to result in a normal offspring. In this process, the semen is inseminated into the female by placing a portion of it either in a collected or diluted form into the cervix or uterus by mechanical methods at the proper time and under most hygienic conditions.
The first scientific research in artificial insemination of domestic animals was performed on dogs in 1780 by the Italian scientist, Lazanno Spalbanzani. His experiments proved that the fertilizing power reside in the spermatozoa and not in the liquid portion of semen. Few further studies under research station conditions helped this technique to be used commercially all over the world including India.
Artificial insemination is not merely a novel method of bringing about impregnation in females. Instead, it is a powerful tool mostly employed for livestock improvement. In artificial insemination, the germplasm of the bulls of superior quality can be effectively utilized with the least regard for their location in faraway places. By adoption of artificial insemination, there would be considerable reduction in both genital and non-genital diseases in the farm stock.
Symptoms of Heat
The various symptoms of heat are
- The animal will be excited condition. The animal will be in restlessness and nervousness.
- The animal will bellow frequently.
- The animal will reduce the intake of feed.
- Peculiar movement of limbo sacral region will be observed.
- The animals which are in heat will lick other animals and smelling other animals.
- The animals will try to mount other animals
- The animals will standstill when another animal try to mount. This period is known as standing heat. This extends for 14-16 hours.
- Frequent maturation (urination) will be observed.
- Clear mucous discharge will be seen from the vulva, sometimes it will be string like the mucous will be seen stick to the near the pasts of valva.
- Swelling of the valva will be seen. Congestion and hyperemia of membrane.
- The tail will be in raised position.
- Milk production will be slightly decreased
- On Palpation, uterus will be turgid and the cervix will be opened.
Advantages and Disadvantages of AI
Advantages of Artificial Insemination
There are several advantages by artificial insemination over natural mating or servicing.
- There is no need of maintenance of breeding bull for a herd; hence the cost of maintenance of breeding bull is saved.
- It prevents the spread of certain diseases and sterility due to genital diseases’: contagious abortion, vibriosis.
- By regular examination of semen after collection and frequent checking on fertility make, early detection of interior males and better breeding efficiency is ensured.
- The progeny testing can be done at an early age.
- The semen of a desired size can be used even after the death of that particular sire.
- The semen collected can be taken to the urban areas or rural areas for insemination
- It makes possible the mating of animals with great differences in size without injury to either of the animal.
- It is helpful to inseminate the animals that refuse to stand or accept the male at the time of oestrum.
- It helps in maintaining the accurate breeding and cawing records.
- It increases the rate of conception
- Old, heavy and injured sires can be used.
Disadvantages of AI
- Requires well-trained operations and special equipment.
- Requires more time than natural services.
- Improper cleaning of instruments and in sanitary conditions may lead to lower fertility.
- If the bull is not properly tested, the spreading of genital diseases will be increased.
- Necessitates the knowledge of the structure and function of reproduction on the part of operator.
Semen collection methods and evaluation
Various methods of collection of semen have been devised from time to time. The older unsatisfactory methods have been gradually replaced by the new modern techniques. There are three common methods.
- Use of artificial vagina
- By Electro-stimulation method.
- By massaging the ampulae of the ductus differences through rectal wall.
The ideal method of semen collection is use of artificial vagina which is safe for sire and the collector also.
Artificial Vagina Method
The artificial vagina has the following parts:
- A heavy hard rubber 2" lose, open at both ends with a nostle for air and water in and outlet.
- Inner sleeve of rubber or rubber liner.
- The semen receiving cone or rubber cone.
- Semen collection tube made of glass or plastic graduated in CC and its fraction correct to 0.1 CC
- Insulating bag : Before using for semen collection all the parts are washed thoroughly and sterilized properly, and assembled as artificial vagina, the rubber liner is inserted into the hose; inverting both ends back by folding back from either side opening, and fastening with rubber bands. Now the space between the hard rubber hose and inner rubber liner forms a water tight compartment. The nostle at one end of the hose can be fixed.
- The water jacket of the Artificial vagina is filled with hot water at a temperature of 45°C (113°F) by opening the nostle.
- The graduated semen collection tube is fixed to the narrow end of the artificial vagina hose, and fastened by a rubber band.
- The inner side of the rubber liner on the anterior side of the artificial vagina is lubricated with sterile jelly to a length of 3 to 4 inches.
- Air is blown through the nostle into the water jacket, to create pressure in it, and the same is exerted to the rubber linear, to simulate natural vagina.
- The temperature of the artificial vagina is to be checked, at each collection, and it should simulate natural vagina at mounting time.
- If it is too cold ejaculate may not be there after a thrust, or even if ejaculate is there; it may be contaminated with urine, and becomes unfit for use.
Semen collection method
The cow or dummy is secured in service create. The artificial vagina assembled is held at 45° angle from the direction of penis, and the thrust is at that angle. The artificial vagina is held with the left hand by a right-handed person; and when the bull mounts the cow, the sheath of the bull will be graphed by the operator, directing the gland penis into the artificial vagina, and then the bull gives a thrust to ejaculate.
The operator should evince care so as not to touch the exposed past of the penis. After the bull dismounts, the artificial vagina is taken off from penis and the air vent is opened to release the pressure from the jacket.
The water from the jacket is also drained by opening the nostle. This allows the ejaculate to flow from the cone to the semen collection tube. The semen collection tube is detached from the cone, plugged with cotton wool, and taken to the laboratory for examination. The rubber cone and the semen collection tube can be protected from external contamination or heat or higher, by covering with an insulation bag with zip.
- The discovery that bull semen could be successfully frozen and stored for indefinite periods has revolutionized AI in cattle.
- In 1949, British scientists discovered that addition of glycerol to the semen extender improved resistance of sperm to freezing. Glycerol acts to remove water from the sperm cell prior to freezing and prevents the formation of cellular ice crystals which would damage the sperm.
- There are two methods of freezing and storing semen: dry ice and alcohol (-100 degrees F) and liquid nitrogen (-320 degrees F). Liquid nitrogen is preferred because there is no evidence of fertility deterioration with age. Fertility gradually declines in semen stored in dry ice-alcohol.
- Frozen semen can be stored indefinitely if proper temperature is maintained. Fresh, liquid semen can be successfully stored for 1 to 4 days at 40 degrees
- Semen is usually stored in glass ampoules. Other method that appears promising is the French-straw.
- Artificial coloring is frequently added to semen extenders in order to distinguish one breed from another. Complete identification of the bull is required on each individual semen container.
- Freezing of semen is done with a special diluent, which has the following composition.
- Sodium citrate dihydrate (angular) 2.4 y. 2.0 gm, 8.0 ml 25.0% by volume 50,000 units per 100 ml of semen Fructose Glycerol Egg Yolk Penicillin dilulent.
- Dihydro-streptomycin 50.0 mg per 100 ml of semen dilulent.
- Distilled water double glass distilled 100 ml.
- The addition of glycerol to the dilulent makes the cells more resistant to the rigours of freezing and icy crystals, which form are smaller and smoother thus creating less damage to the spermatozoa. The addition of fructose to the diluent luprores sperm resistance to glycerol; and also provides nutrition.
- Frozen semen is packed in single dose glass vials or plastic straws at +5°C.
- The final level of glycerol should be 7.0 to 7.6% during the freezing process.
- The antibiotics are added to inhibit bacteria and to kill pathetic organisms.
- The semen to be diluted in such a way that one ml. of extended semen will contain 20 million motile spermatozoa.
- The semen must be cooled carefully for spermatozoa to remain with life. The final temperature is lowered to -79°C or still lower.
- Quick freezing is done for a period of 3 to 5 minutes to -75°C with the help of atmosphere created by liquid nitrogen. In the slow freezing technique cooling is done at the rate of 1 °C per minute from +5°C to -15°C. From -15°C to -31 °C at the rate of 2°C per minute. From -31°C to 75°C at the rate of 4 to 5°C per minute. Thus, taking 40 minutes in total, further cooling to -96°C can be done quickly as it is not critical after freezing.
- Before freezing the diluted semen in equilibrated for 3 to 5 hours or for the best 16 to 20, hours period in refrigerator at 5°C.
- Liquid nitrogen plays a vital role for storing the frozen semen straws, at a temperature of -196°C for longer periods.
There-are different methods of insemination in different species of animals i.e. speculum method, vaginal method and recto vaginal method.
Recto Vaginal Method
Recto vaginal method
- In cattle the safe and best method of insemination is “Recto vaginal method of insemination”.
- Cow which is in heat is well controlled placing it in a Travis.
- The inseminator will get ready by wearing a plastic apron, gumboots and gloves.
- The semen straw after thawing (keeping the semen straw in warm water for a minute to convert the freezed semen into liquid and the sperms become motile) is loaded in a sterilized A.I. gun covered with a plastic sheath.
- The inseminator will insert the gloved left hand into the rectum after applying the soft soap or other lubricant on the glove and back racked the animal, and the hand is further inserted and will catch hold the cervix through rectal wall.
- The A.I gum loaded with semen straw is passed through the vulva to ‘vagina and cervix and observed with the hand in rectum that the A. I gum reaches the cervix, then the semen is deposited by injecting the gun, and after depositing the semen the gun is removed, the empty straw and sheath are disordered.
- In this method, spectrum is placed in the vagina of the cow, which provides passage outside to the site of insemination, then inseminating tube is passed through the speculum and semen is deposited at the cervix.
- Hand is passed through the vagina and the inseminating tube is guided by hand to the site of insemination and semen is deposited. Here there is a risk of contamination and injury of female genitalia.
Timing of Insemination for Maximum Conception
A frequent question concerning AI is: What time during estrus should cows be bred for greatest chance of conception? Since estrus may last from 10 to 25 hours there is considerable latitude in possible time of insemination. Much research work has been conducted on this subject. The studies show that conception rate is lower when cows are bred prior to mid estrus or later than 6 hours after cessation of estrus (standing heat in this case).
Maximal conception is obtained when cows are inseminated between mid-estrus and the end of standing estrus, with good results up to 6 hours after estrus. Success in insemination timing is dependent upon a good heat detection program. In large herds, this means assigning individual responsibility for heat detection and a continued education program for labor. A successful heat detection program and subsequent proper timing of insemination will pay dividends in increasing reproductive efficiency.
Source : Pashu sakhi Handbook