Artificial Insemination – SS3 Agricultural Science Lesson Note (First Term)

Artificial insemination (AI) is the introduction of semen from a male into the reproductive tract of a female by means other than natural mating.

• Main use: livestock breeding, such as cattle, sheep, goats, pigs and poultry.
• Other use: sometimes used in human fertility treatment.

Behavioural objectives

1. Define artificial insemination.
2. Name and describe four methods of collecting semen for AI.
3. List the steps in carrying out AI.
4. Describe how semen is examined and stored.
5. State the advantages and disadvantages of AI.

What are the key terms in artificial insemination?

These are the five words used most often when studying AI.

• Semen: the fluid from the male that carries sperm cells.
• Insemination: placing semen in the female reproductive tract.
• Heat (oestrus): the period when a female is ready to mate and can become pregnant.
• Extender: a liquid added to semen to increase its volume and keep sperm alive.
• Teaser: a female or dummy animal that the male mounts during collection.

What are the methods of collecting semen for AI?

There are four methods of collecting semen for AI: artificial vagina, massage, electro-ejaculation and recovery from the vagina after service.

1. Artificial vagina method

• How it works: the male mounts a female or dummy and ejaculates into an artificial vagina.
• Artificial vagina: a tube with warm water inside and a collecting tube at one end.
• Use: common for bulls, rams and stallions.
• Next step: the semen is checked, processed and used for insemination.

2. Massage method

• How it works: the handler stimulates the male’s body or genital area by hand to cause ejaculation.
• Use: common in poultry, such as cockerels and turkeys.
• Next step: the semen is collected and processed before insemination.

3. Electro-ejaculation

• How it works: mild electrical stimulation is applied to the nerves that control ejaculation.
• Use: for males that cannot or will not ejaculate naturally, such as injured or unwilling animals.
• Care: a trained person must carry it out so that the animal is not hurt.

4. Recovery of semen from the vagina after service

• How it works: semen is collected from the female’s vagina after natural mating.
• Quality: the semen is mixed with vaginal fluid, so it is of lower quality.
• Next step: it is processed for use in further inseminations or breeding programmes.

How do the collection methods compare?

The four methods differ in the animals they suit and in how ejaculation is caused.

What is checked when semen is examined?

Semen is examined to confirm that it is good enough for insemination.

• Volume: the amount of semen collected.
• Colour: healthy semen is usually creamy or milky, and unusual colour may show infection.
• Motility: the number of sperm cells that move actively.
• Concentration: the number of sperm cells in a given amount of semen.
• Abnormal cells: semen with many deformed or dead sperm is rejected.

How is semen stored for AI?

Semen is stored either chilled for short use or deep frozen for long storage.

How do you detect heat in a female animal?

Heat is detected by watching the female for changes in behaviour and body signs.

• Restlessness: the animal moves about and may stop feeding well.
• Mounting: the female mounts other animals or stands still to be mounted.
• Swollen vulva: the vulva becomes red and swollen.
• Mucus discharge: clear mucus flows from the vulva.

What are the steps in carrying out AI?

1. Select a healthy male of good breeding and a healthy female.
2. Collect semen by one of the methods above.
3. Examine the semen for volume, colour and the number of active sperm cells.
4. Add an extender to the semen to dilute it and keep the sperm alive.
5. Store the semen, chilled for short use or deep frozen in liquid nitrogen for long storage.
6. Detect heat in the female by signs such as restlessness, mounting other animals, swollen vulva and mucus discharge.
7. Place the semen in the female’s reproductive tract with a clean insemination instrument at the right time in heat.
8. Record the date and watch the female for pregnancy.

What are the advantages of AI?

The main advantage of AI is that one superior male can father many offspring.

• Better breeds: semen from one superior male can serve many females.
• Lower cost: farmers need not keep many breeding males.
• Disease control: it reduces the spread of diseases passed on during mating.
• Safety: it avoids injury when a heavy male mates with a small female.
• Distance: semen can be sent to farms far away or kept for years when frozen.
• Records: breeding is easier to plan and record.

What are the disadvantages of AI?

The main disadvantages of AI are the cost, the skill needed and the risk of wrong timing.

• Skill: it needs trained workers and special equipment.
• Cost: equipment and storage in liquid nitrogen are expensive.
• Heat detection: wrong timing leads to failure to conceive.
• Disease spread: infected semen or unclean tools can spread disease.
• Inbreeding: using one male too widely can narrow the gene pool.
• Access: it is hard to practise in remote areas without power or trained staff.

Evaluation

1. What is artificial insemination?
2. Name four methods of collecting semen for AI and describe each.
3. List the steps in carrying out AI.
4. State three signs of heat in a female animal.
5. State three advantages and three disadvantages of AI.

Assignment

Draw a table of the four semen collection methods. Give one animal and one feature for each.