Soni Kumari1, Priyanka Kumari2, Archita Singh3 1Ph.D. Scholar, Division of Animal Genetics, 2Ph.D. Scholar, Division of Parasitology, 3Ph.D. Scholar, Division of Physiology and Climatology, ICAR- Indian Veterinary Research Institute, Izatnagar
Artificial insemination (AI) is the most widely used reproductive technology in the livestock industry. Its adoption in poultry species has increased in popularity, especially in the western countries for research and commercial purposes. AI in chicken requires one to understand the basic anatomy and physiology of the hen’s and the cock’s reproductive tract. AI involves the deposition of semen into female reproductive tract manually. It starts with the collection of the semen from the male and its evaluation in terms of motility, viability and concentration followed by its deposition into female reproductive tract. One must be technically competent with the semen collection and deposition procedures in order to achieve effectiveness in producing fertilized eggs. Males can produce semen as early as 12 weeks of age, depending upon body size and lighting programme. However, sperm from such roosters is rarely viable and effective; maturity does not develop until birds are around a minimum of 18 weeks of age. So the cocks from 22 or 24 weeks of age are used for semen collection. Semen consists of spermatozoa and seminal plasma. Fowl semen is generally highly concentrated (3 to 8 billion spermatozoa per ml for broiler fowl). The natural colour of poultry semen is white or pearly white. Heavy breed male can produce 0.75 to 1 ml semen and light breed male can produce 0.4 to 0.6 ml of semen. Chicken semen begin to lose fertilizing ability when stored >1 hour. Liquid cold (4°C) storage of chicken semen can be used to transport semen and maintain spermatozoa viability for ~6–12 hours. Semen is collected 4–6 times in a week. Although every day semen collection will not change the fertilizing capacity but the volume of semen will be low. Inseminations should be carried out on two consecutive days at the first week and then once each week thereafter while fertile eggs are required. As poultry semen has a very limited life, insemination of hens should be complete within one hour of semen collection. It is a good idea to carry out the operation at the same time each day, the best time being between 2.00 and 4.00 pm. The reason for this is that during the morning, most hens have an egg in the oviduct, thus obstructing the free passage of semen to the ovary. Another point in favour of inseminating the hens in the afternoon is that it is generally cooler and the hens are less likely to be affected by heat, particularly in late spring. Equipment needed for AI: small glass funnel with stem plugged with wax, inseminating syringe, wide mouthed glass vial, small pyrex semen cup, large flask to hold water at 180°C to 200°C range for short time holding of semen.
Semen collection: The first step in AI program is manual collection (milking) of the semen. A team of two members should be involved in semen collection, one for restraining the male and the other for collecting semen. The bird should be held in a horizontal position by a person at a height convenient to the operator who is attempting to collect the semen. To collect semen the operator should place the thumb and index finger of the left hand on either side of the cloaca and massage gently. By his right hand the operator should hold a collecting funnel and with the thumb and index finger massage the soft part of abdomen below the pelvic bones. Massage should be rapid and continuous until the cock protrudes the papilla from the cloaca. Once the papilla is fully protruded, the previously positioned thumb and index finger of the left hand are used to squeeze out the semen in to the collecting funnel. Avoid contamination of semen with faeces and feather. Semen should be evaluated after collection. Normal colour of the semen in pearly white or cream coloured. Yellow semen and semen contaminated with blood, urates, faeces or other debris should be avoided. Semen should not be allowed to come in contact with water. If debris or contaminants are observed in pooled semen, carefully aspirate contaminates from the sample before mixing with additional diluent with the semen. Diluted semen should be kept in a cooler or refrigerator (3 to 12°C) to cool down. Chicken semen begins to lose fertilizing ability when stored >1 hr. Liquid cold (4°C) storage semen can be used to transport semen and maintain spermatozoal viability for ~6–12 hr. Chicken semen may be frozen, but reduced fertility limits usage to special breeding projects.
Insemination: All equipment to be used for insemination should be thoroughly cleaned and dried before use. Insemination must be carried out when majority of the birds have completed laying since a hard shelled egg in the lower end of the oviduct obstructs insemination and lowers fertility. In practice, inseminating chicken after 3 pm obtained better results. It is difficult to inseminate non-laying hens. Usually insemination is done when the flock reaches 25% egg production. Hens are inseminated twice during first week, then at weekly intervals. Under experimental conditions, fertility levels of 90% have been obtained in hens inseminated at 3-day intervals with 400–500 million frozen-thawed chicken spermatozoa. In chickens, the number of diluted semen inseminated will range from ~100–200 million sperm cells per insemination. In chickens, because of the lower spermatozoon concentration and shorter duration of fertility, 0.05 mL of undiluted pooled semen, at intervals of 7 days, is required. The hen’s squatting behavior indicates receptivity and the time for the first insemination. Fertility tends to decrease later in the season; therefore, it may be justified to inseminate more frequently or use more cells per insemination dose as hens age. Procedure: For insemination hen is held upright by the legs with the left hand down and tail tucked back and against the operator chest. The thumb of the right hand is placed against the upper lip of the vent then with a rounding motion abdomen muscles are pressed, particularly on the left side. Do not squeeze with fingers but apply pressure evenly with the palm of the hand. This causes the cloaca to evert and the oviduct to protrude, the second operator inserts the syringe or plastic straw ~1 inch (2.5 cm) into the oviduct and the appropriate amount of semen is deposited at the junction of vagina and uterus. As the semen is expelled by the inseminator, pressure around the vent is released, which assists the hen in retaining sperm in the vagina or oviduct.
Advantages : Some of the advantages of artificial insemination in the poultry are: 1. Normally one cockerel can be mated to six to ten hens. With artificial insemination this mating ratio could be increased fourfold. This way one male of high genetic merit for a particular trait of interest can be used to serve more females. 2. Older males having outstanding performance can be used for several generations whereas under natural mating their useful life is limited. 3. Valuable male birds having the leg injury can still be used for artificial insemination. 4. When there is poor fertility caused by preferential mating, it can be eliminated. 5. Although cross breeding is very successful under natural conditions, but sometimes there is a kind of colour discrimination as some hens will not mate with a male of a different colour unless they have been reared together. In such condition AI helps in successful cross breeding. 6. AI allows for incompatible individuals to mate; incompatibility arises when males are heavier than females and under natural mating this may result to injury of the females. 7. AI allows for better use of the cage feeding system in hatchery operations, especially when dealing with large number of females that are required to lay fertilized eggs.