Advantages of artificial insemination
- The greatest advantage of artificial insemination is the opportunity to spread superior germ plasm by the wide use of carefully tested and selected sires. On average, a bull can sire 50,000 progeny per year through artificial insemination compared to 40 - 50 progeny through natural mating.
- Artificial insemination plays an important role in the control of various diseases, particularly the venereal diseases disseminated by natural mating.
- It helps to maintain complete and accurate breeding records, leading to better herd management and the identification of infertility problems.
- Artificial insemination is more economical than natural mating.
- The mating of animals of different sizes becomes possible without any accidental injury.
- Artificial insemination extends the usefulness of sires of high genetic merit which for physical reasons are unable to copulate normally.
There are few disadvantages of artificial insemination even if it is properly performed. The major limitations are due to lack of trained personnel to provide proper service. Poor breeding efficiency may occur in herds when owners do not watch their animals closely for estrus and the inseminator does not breed them at the proper time. The inseminator may be, if not careful, a means of spreading infections from one herd to another. Herd owners should avoid intensive use of a limited number of sires, which may increase inbreeding in the herd. Increased inbreeding is usually associated with low fertility and decrease in vigor and overall productivity.
Semen and its collection
One of the most important steps in an artificial insemination program is the collection of semen and its proper handling. The following methods are used for the collection of semen from bulls.
- Artificial vagina method
- Massage Method
- Electro-ejaculation method
In the massage method, the operator's hand is inserted about 10 inches into the rectum of the bull. The vesicular glands are picked up with the fingers by carefully feeling the rectal wall. They are then massaged gently causing a slightly turbid fluid to appear which cleanses the path for semen. Then the operator massaages the ampulla of the vas deferens until the sperm containing semen appears. The semen is collected in a test tube placed in front of the sheath.
Electro-ejaculation is the method used for males that refuse to serve the artificial vagina or when injuries makes this impossible. A rectal probe with either a ring or straight electrode is used to provide the necessary electrical stimulation.
After the semen is collected, it is evaluated for quality (live and dead sperm, motility etc) and diluted with suitable extenders (diluent). Then it is stored in liquid form in the refrigerator at 5 Degrees Celsius or in frozen form in liquid nitrogen at below 196 Degrees Celsius.
Detection of heat (estrus) of the female is the first step. When a female is found to be in heat, the inseminating rod is passed through the spiral folds of the cow's cervix by the recto-vaginal technique. Part of the semen is deposited in the uterus, just inside the cervix, and the remainer in the cervix while the rod is withdrawn. Extra care must be exercised in the case of those animals that have been inseminated previously. If pregnancy is suspected in an animal, insemination should not be repeated.
Spermatozoa can survive in the genital tract of a cow or buffalo for a little over 24 hours. The egg has a short survival time, about 6 hours at the most. Optimum fertility is obtained when inseminations are performed 13-18 hours before ovulation. Reasonably good results are obtained even during the period 7-12 hours before ovulation. The cows should be checked twice daily with a teaser bull to detect estrus. As a rule of thumb, cows showing estrus in the morning should be bred the same day in the afternoon, and cows showing estrus in the afternoon should be inseminated the next morning.