Maximising ram fertility

The health and wellbeing of your rams will directly affect their fertility, so you must make sure they are well nourished and healthy.

Sperm production in rams takes 49 days. You must ensure rams are well looked after during the 7–8 week period leading up to joining, to avoid factors that could adversely affect the sperm and lead to temporary infertility.

Checking sperm reserves

The epididymis is a part of the ram's testicles that absorbs testicular fluid and enables large quantities of sperm to be stored in the smallest possible space. It's located in the back rear section of each testicle.

Checking the tail of the epididymis can give you a useful guide to the level of sperm reserves in rams. A large, firm (but not hard and diseased) epididymis is an indication of good reserves, while a small, soft tail indicates the opposite.

Testicle size

Testicle size is a good indication of the sperm producing ability of individual rams. Sperm are produced by testicular tissue at a reasonably constant rate of about 20 million sperm per gram of testis per day.

You can check the size of a ram's testicles for a reasonably good judgement of the ram's stores of sperm. Large testicles can also be an indicator of higher levels of testosterone, which is an important factor in the ram's sexual interest.

It's important to avoid selecting rams with small testicles, as this is equally likely to be a sign of low sperm availability in the animal.


For normal sperm production to occur, the testes need to be kept cool. A ram's natural cooling mechanism includes large sweat glands in the skin of the scrotum and a system of muscles that raise or lower the testes into the body for the purpose of temperature regulation. Blood flow to the testes also helps to regulate temperature through a heat exchange mechanism.

Hot weather, such as long periods of temperatures over 32 degrees Celsius, or short spells of very high temperatures (38 degrees Celsius or higher), affects the production of viable sperm. Rams that are heat stressed before joining could still successfully serve ewes up until the sperm stored before the heating are used (about 2–3 weeks), but it will then take 7 weeks to produce new viable sperm.

Before and during joining:

  • ensure rams have adequate shade in the paddock
  • continually look out for fever resulting from fly strike or infection.


Nutrition has a direct and dramatic effect on testicle size and sperm production. Improving nutritional intake of protein and energy during the 2-month period before joining can increase, and sometimes double, sperm production.

You should aim to have rams at a condition score of 3.5 at joining. Don't allow rams to become overweight, with a condition score of more than 4. Overweight rams tend to be less sexually active and are more prone to heat stress.

Vitamin A

Vitamin A is important to sperm production, so you should ensure your rams have access to green feed. Rams deficient in vitamin A have soft testicles and produce poor quality sperm. Where rams have gone for 6 months or more without access to any green feed, supplements containing vitamin A may be needed (e.g. green hay or vitamin concentrate).

Mature sheep have sufficient stores of vitamin A to survive for 8–12 months without green feed and without showing signs of vitamin A deficiency.


Rams are prone to several infectious diseases that need to be kept under controlled, as they can have serious effects on fertility.

Each year, you should thoroughly examine rams 12 weeks before. This will help detect any issues that warrant culling and allow time to find replacement rams if required.

Trimming horns, hooves and shearing are also important in keeping rams healthy and should be done at least annually, ideally 12 weeks before joining

Use the checklist for ram checks from for more information.

Ovine brucellosis

Ovine brucellosis can cause swelling in the ram's sperm duct, which subsequently blocks the transfer of sperm. This condition is known as epididymitis and may reduce fertility or, if both testicles are affected, cause total infertility.

Brucellosis can sometimes be managed in a flock by:

  • culling rams with clear testicular abnormalities
  • using a higher joining percentage.

However in some instances it may be more beneficial to talk to your veterinarian about eradicating the disease.

Ensure you don't introduce infected rams to your flock by checking all new rams. If possible, keep new animals separate for 8 to 12 weeks to allow any infected rams to show detectable lesions

Cheesy gland

Cheesy gland (caseous lymphadenitis) is a common bacterial disease of sheep, also known as shearer's boils, yolk boils or CLA.

Cheesy gland abscesses often occur in the scrotum and can be found by palpation in the cords above the testicles. They can be easily detected as a hard lump up to about the size of an egg. If cut open, a large quantity of greenish-yellow pus will be obvious.

Cheesy gland is likely to interfere with temperature regulation of the testes as well as cause inflammation and some pain and discomfort, which are all capable of reducing fertility, ability and stamina.

There is no cure for cheesy gland but you can prevent it through a 6-in-1 vaccination program.