Preservation and Artificial insemination

Animal husbandry is the branch of agriculture that involves the rearing and breeding of livestock such as pigs, horses, goats, sheep, and cattle. Mating animals can be done in two ways: natural propagation/mating or artificial insemination. This was first carried out by an Italian scientist Lazanno Spallanzani who performed the procedure on dogs. Artificial insemination requires sperm collection and preservation, along with animal husbandry techniques. 

Artificial insemination Overview

Artificial insemination is the technique of deposition of collected semen containing living sperm cells of a male animal into the vaginal tract of the female. The semen can be collected either through an artificial vagina or by the electro-stimulation method. However, the artificial vagina method is preferable as it is safe for both the animal and the collector. The deposition of semen in the reproductive system of the female can be done by speculum method, vaginal method, or rectovaginal method. The chance of conception is maximum when the cattle are inseminated between the mid-estrus period and the end of the standing-estrus period, with a desirable outcome up to six hours after estrus. However, in India, this technique is considered a ‘cruelty’ to animals, for it deprives the bulls and cows of their right to copulate. 

Preservation of Semen

For the successful preservation of spermatozoa, freezing of semen for longer periods is of great importance to farm management and animal breeding. To improve the freezing capacity of sperm, glycerol is added to the semen. Before freezing, glycerol is added to the sperm cell for removal of water which restricts the formation of cellular ice crystals that can cause damage to the sperm. For freezing and preserving semen, either dry ice-alcohol or liquid nitrogen can be employed. Liquid nitrogen is preferable to dry ice alcohol as there is no decline in fertility rate concerning time. However, when stored in dry ice, alcohol there has been evidence of gradual fertility degradation in semen.

Semen can be preserved in frozen form for an indefinite period, given proper temperature is maintained. Preservation of fresh liquid semen can be accomplished for four days at 4 degrees Celsius. To differentiate between semen collected from different breeds, artificial colouring is added to the semen extenders.

The transportation of the collected semen for insemination can be done from rural to urban areas and vice-versa. The preservation of semen and its utilisation in artificial insemination procedures makes the mating of different sizes of animals possible without injury to either animal. For example, the semen from one bull can be used to impregnate a few thousand cows located in far-off places. 

Superovulation and Embryo Transplantation

Even by artificial insemination, the success rate of crossing mature males and females is relatively low. Multiple Ovulation Embryo Transfer Technology is employed to enhance the success rate of hybrid production. This technique involves the treatment of a high-yielding cow with FSH hormone to induce superovulation. This cow is then artificially inseminated with the preserved semen of a bull. After the female is impregnated, 4-10 embryos are collected at a time. The embryos at the 8-32 cell stage are recovered and then transferred to different surrogate mother cows. The offspring obtained by this method may grow into a high-quality bull or super milk cow. The week-old embryos can be preserved for several years by deep freezing at -190 degrees Celsius. This technology is being used not only on cows but also on sheep, horses, and even rabbits.

Advantages 

• Males of high-yielding breeds can be kept in an environment most suitable to them.
• Semen can be collected from the bull and preserved for usage at distant places, while transportation of the bull is not practicable. It is highly effective for old, heavy, and injured bulls.
• The semen can be frozen and preserved indefinitely and used later. The semen can be used even after the death of a particular superior sire.
• It is economical as the semen of a single male is adequate to impregnate a considerable number of females.
• Diseases such as contagious abortion and vibriosis do not spread by this technique. 
• As more offspring can be produced from a single male using this technique, fewer males are needed. This increases the genetic selection and allows the selection of only a few best males for use as sires.

Disadvantages 

• Special equipment and well-trained operations are required.
• This technique usually takes more time than natural breeding.
• Insanitary conditions and unhygienic instruments may result in lower fertility.
• There is a risk of spreading genital diseases if the bull is not properly tested.
• Superior bulls will be more desired, and the market for other bulls will be reduced.
• Artificial insemination in India is considered a ‘cruelty’ to animals, for it deprives the bulls and cows of the pleasure of natural mating.

Conclusion

Artificial insemination is a controlled breeding technique where semen collected from a male animal is introduced into the female reproductive system by the breeder. It is an economically useful technique that is employed for livestock improvement. It helps in the fertilisation of a large number of animals, and the progeny obtained is healthy and resistant to diseases. However, it is time-consuming, and if there is an error in bull testing, then it may also lead to the spread of genetic diseases.

The success rate is increased by the Multiple Ovulation Embryo Transfer Technology (MOET) technique, leading to the production of super milk-yielding breeds of females and high-quality bulls.