Artificial insemination of livestock
Artificial insemination of livestock is a common practice in Kenya especially for breeding dairy cattle. The impact of AI is much deeper than simply another way to impregnate. Other farm animals like sheep, horses, pigs, dogs, poultry and honeybees can be bred using this method as it provides an economical means for livestock breeders to improve their herds using males with desirable traits and with the least regard for their location in far away places.
The Central Artificial Insemination Station (CAIS) which was established in 1946 is charged with the production of semen. The station has bulls from the four dairy breeds, Ayrshire, Friesian, Guernsey and Jersey; but the Simmental, the Hereford, Charolais and Brown Swiss bulls were phased out by the year 1992 due to decreased demand for their semen. It works in collaboration with international companies like WWS, ABS, Semex and HighChem (E.A. Dairy). Another organization, Holland Genetics imports and distributes semen via Cooper Kenya Ltd. So there are reliable sources of cattle semen in the country.
Earlier on the government had a network of AI routes and services but it was reorganized and privatized. AI service is now in private hands carried out by technicians from approved AI training centers or by qualified vets. Many Farmers Cooperative Societies in the country have trained inseminators who provide insemination service to members of its organization.
Although professional technicians are more successful at insemination than inexperienced owners Artificial Insemination can be done on a DIY basis by qualified farmers on their own cows. The insemination process is simple to understand but it requires sufficient manipulative skill. Regular practice at inseminating is vital to maintain high conception rates. The timing must be precise therefore detection of heat in cattle by the farmer is very critical.
Semen collection, evaluation, packaging and storage
AI starts with the collection of semen from bulls. There are three common methods of collecting semen i.e. by use of artificial vagina, electro-stimulation, and massaging the ampulae of the ductus differences through the rectal wall. The ideal method of semen collection is use of artificial vagina which is safe for both the sire and the collector. Semen from a bull can be collected approximately 2 – 4 times a week. The bull is induced to ejaculate into the artificial vagina. Then the semen is checked for contaminants such as blood, pus or feces. Microscopic examination of spermatozoa follows.
Test of sperm quality by the assessment of the proportion of normal, progressively moving sperm through a microscope is done. The sperm is evaluated for motility and morphology, ejaculate volume and sperm concentration because they determine the number of sperm obtained.
Semen is then diluted in an extender which provides an appropriate concentration of spermatozoa, allowing more inseminations from each sample. A dilution of around 50 times is usual. The extender also nourishes and protects the spermatozoa during storage and distribution. In CAIS a coconut milk extender is used for room-temperature semen. For deep frozen semen an extender containing glycerol is used and the semen is then packed in 0.5 ml plastic straws in liquid nitrogen.
Semen is packaged in glass ampoules (vials) or plastic straws holding between 0.25 ml to 0.5 ml of semen. There are two methods of freezing and storing semen: dry ice and alcohol (-760 C) and liquid nitrogen (-1960 C). Liquid nitrogen is preferred because fertility does not deteriorate with age. Fertility gradually declines in semen stored in dry ice-alcohol. Identification of the bull is done on each individual semen container. Each straw contains around 20 million spermatozoa. Fresh, liquid semen can be successfully stored for 1 to 4 days at 40 C.
Frozen bull semen can be stored indefinitely, if it is maintained constantly at very low temperatures. The critical temperature is approximately -800C. Exposing semen to temperatures warmer than -800C can damage it, even if just momentarily and returning it to the storage tank.
Straws are thawed in warm water for a few seconds before insemination to reactivate the spermatozoa. The straw is then fitted into a special insemination gun (catheter) which is inserted into the cow's vagina and positioned so that the semen is deposited beyond the cervix.
One of the most dramatic technical advances in recent years is the sexing of sperm by DNA quantification using flow cytometry instrumentation.
Timing Artificial Insemination
Accurate detection of estrus is a problem on many farms. A frequent question concerning artificial insemination is what time is best to inseminate a cow for greatest chance of conception. Since ovulation occurs about 12 hours after the end of standing heat, insemination should be carried out 12-24 hours after the beginning of estrus to ensure that sperm arrive at the site of fertilization a few hours before ovulation. Conception rate is lower when cows are bred a few hours on either side of this target, and decreases significantly when breeding occurs more than 12 hours away from the end of “standing heat”. Estrus can last from 10 to 25 hours.
A rule of thumb that works well for timing AI is called the AM/PM rule. The classic rule states that for best fertility, cows first seen in estrus in the AM should be inseminated during the afternoon of the same day. Cows first seen in estrus in the PM should be inseminated before noon the next day.
Cows showing estrus
Should be inseminated
Tool late for good results
Morning of next day or early afternoon
After 3 p.m.
Artificial Insemination methods
The speculum, vaginal and recto vaginal are the three different methods of insemination used for different species of animals. In cattle the safe and best method of insemination is the recto vaginal method of insemination.
Recto-vaginal method of insemination
After applying lubricant the inseminator insert s the gloved left hand into the rectum of the restrained animal to hold the cervix through rectal wall. The A.I gun loaded with semen straw is passed through the vulva to vagina and cervix then the semen is deposited by injecting the gun. The gun, the empty straw and sheath are removed after depositing the semen.
A spectrum is placed in the vagina of the cow provides passage for an inseminating tube through which semen is deposited at the cervix
The inseminator passes the hand through the vagina and guides the inseminating tube to deposit semen at the cervix. Risks of contamination and injury of female genitalia are high in this method.
One of the major reasons for Artificial Insemination is to make the males that transmit superior genetics for milk production available to more producers in the animal industry. The elite bulls is made available to all and not limited to the wealthy.
Use of AI in other farm animals
Beef cattle greatly outnumber dairy cattle in Kenya. The technology of semen handling and insemination of beef cows is similar to that used for dairy cows, but beef cows are not managed as conveniently for AI. Many cows are on extensive ranges where detection of estrus and rounding up animals in estrus for insemination is not cost-effective. Therefore, the proportion of beef cattle bred by AI is low. Where small groups of beef cows are kept in close confinement, estrous cycle can be synchronized to facilitate insemination for a group at a time. In crossbreeding programs, AI has the advantage because semen can inexpensively replace maintaining bulls of separate breeds.
Boars are trained to mount dummies. Artificial vaginas developed for boar semen collection provide a means of collecting the boar semen.
Pregnancy rates and litter sizes are reduced with cryopreserved boar sperm, so frozen semen is limited to use in special breeding programs. Fresh or extended liquid semen is used for about 99% of AI in pigs.
However rapid transport of extended semen can make it possible for pig farmers to take advantage of commercially produced boar semen.
Techniques for evaluating quality of boar sperm are similar to those used for bull sperm. Sexing of boar sperm is possible but is too slow to produce sexed sperm for commercial use.
Collection of semen is by use of artificial vaginas and semen evaluation is similar to the evaluation of bull semen. Although methods have been devised to freeze stallion sperm, most equine AI is done with cooled, extended semen used within 48 hours of collection.
Sheep and Goats
There are elaborate techniques for semen collection and artificial insemination in sheep and goats. Both rams and bucks are trained to serve the artificial vagina. However, for obtaining semen from a large number of rams in the field, electro-ejaculation is a used.
Buck sperm cryopreservation is more successful than the cryopreservation of ram sperm. Frozen-thawed semen results in satisfactory fertility in goats provided that the sperm are deposited deep into or through the cervix. In the ewe this is difficult. Therefore, insemination into the uterus with the aid of a laparoscope is necessary to achieve high fertility.
Because of the difficulty of insemination, general management and low value per animal, AI, particularly of sheep, is not widespread.
Artificial insemination has been widely applied to poultry. Abdominal massage and pressure method is used to collect semen. With the ease of collecting poultry semen, and proximity of hens on large breeding farms, AI is used extensively with freshly collected semen. It is used for turkey breeding because mating is difficult. Freshly collected chicken semen is frozen but cryopreserved poultry sperm are less fertile and freezing poultry sperm still is experimental.
Other Domestic Mammals
AI for dogs has only been used in special cases, such as for breeding guide dogs or for overcoming special problems. All the artificial insemination techniques employed with farm animals can be performed with rabbit.