Anatomy

• Boar Anatomy Diagram

The ejaculate

Contents:

Three phases:

• Gel produced by the bulbourethral glands

• Sperm poor fraction containing sugar from the seminal vesicles and proteins and fluid from the prostrate (which produces most of the 150 ml average produced).

• Sperm rich fraction from the testes

Sperm content

Average ejaculate contains 2-12 X 10¹⁰ sperm (2-120,000,000,000)

Quantity

Ejaculates vary from 50 to 350 ml

Weight/volume

1 ml weighs approximately 1 g

Smell

Should have no smell

Amount required per AI insemination

1.5 - 3 X 10⁹ sperm in 50 to 100 ml of diluent

Major events in a sperm's life

Development

3-5 weeks in the testes

Production

6000 per second

Maturation

2 weeks in the epididymis

Storage

In the epididymis- it takes 3-5 days to fill the epididymis

Ejaculation

3-20 minutes

Capacitation

6-8 hours.  The time taken for maturation to allow the sperm to penetrate the egg

Oviduct entry

Only 0.1% of the ejaculate enters the oviducts of the sow

Life span (post-ejaculation)

In the sow 48 hours +

In diluent (BTS) 3 days

The boar should be collected at least every 14 days and to maximise semen production not more than twice a week.  For non-AI boars work load is dependent on age

If semen production is damaged, it can take 6 weeks for the boar to recover.  The reproductive organs are particularly sensitive to heat stress, either from disease or the environment

Sperm anatomy

The acrosome contains the important genetic material (DNA)

The midpiece is full of mitochondria - the power source

The tail propels the sperm forward

The tail is only to move the sperm into the egg, it is not intended to swim up the uterus

Major hormones controlling male reproduction

Hormone

Source

Controls

Testosterone

Testes

Maturation of sperm. Male behaviour.  Male growth

Follicle stimulating hormone (FSH)

Brain

Production of sperm

Luteinizing hormone (LH)

Brain

Testosterone production

Oxytocin

Brain

Ejaculation, pre-coital sexual stimulation

Cortisol

Adrenal

Stress hormone has a negative effect

Phases of sexual behaviour

1

Courtship

2

Mounting

3

Active phase where the boar erects and tries to get the anticlockwise spiral tip of the penis to lock into the cervix of the sow

4

Pre-ejaculation where the boar starts to thrust

5

Production of jelly from the bulbourethral glands, which seals the cervix after finishing service.  This is also produced in small amounts throughout the ejaculation.

6

Seminal fluid production

7

Waves of sperm rich fluid

8

Production of more sperm poor seminal fluids

9

Termination of ejaculation and release of the penis from the cervix

10

Dismounting

Factors which may affect libido