SHEEP MANAGEMENT PRE-MATING: Sexual fitness

This aspect is one that is often overlooked, while it can have significant adverse consequences. The potential negative impact is usually only noticed when it is too late. The main focus here is on the rams, but the ewes should also be examined.

Rams

Determining the sexual fitness of rams before the start of the mating season is often neglected. This can be very expensive - especially if single ram matings are done (one ram per group of ewes), or if ram semen is to be used for fresh semen AI (placement of fresh semen into the cervix via the vagina) or laparoscopic AI (placement of fresh/thawed semen into the uterus via the abdominal cavity using a laparoscope).

Sexual fitness involves much more than just checking whether a ram is fertile (has viable semen). NB. A ram can be fertile but NOT necessarily sexually fit! 

Determining sexual fitness involves the following:

1.  Anatomy

This involves the anatomical suitability of the ram to successfully mate an ewe and includes the examination of the following:

• penis - must be able to fully extend and not be broken/crooked
• scrotum - must be symmetrical, not too long (testis that hang too low are more easily injured) and must not be split at the bottom (negative genetic component).
• testicles - must have a firm consistency, be of equal size, not twisted (one pointing forward and one pointing backward), be without lumps and be large enough for the age of the ram
• feet - claws must not be overgrown and/or cracked
• joints - must not be stiff/injured to prevent a ram from jumping a ewe. Pastern joints must not be too long/flabby

2.  Libido- the ram must be interested in the ewes to be able to do his job. Young rams should also be exposed to a mating test beforehand, to see if they can successfully mate a ewe within a certain time. Some rams are interested and jump but struggle to mate effectively. Furthermore, research shows that 8-10% of young rams may be homosexual

3.  Diseases 

• “Peester” disease (pizzle rot) - can be a problem in some herds that can affect reproduction. It is characterized by a swollen/inflamed sheath opening and ulcerations on the penis. Both rams and ewes should therefore be examined and treated early (long-acting antibiotics - tetracyclines)

• epididymitis (Brucella ovine) - causes infertility and is contagious. Make sure rams purchased are vaccinated and free of epididymitis

4. Semen quality and quantity

Evaluation of semen should include the following minimum analysis/measurements:

• Macroscopically

  • Colour

  • Density

  • Movement

  • Volume

  • % Alive

• Semen smears

  • Semen morphology (head/tail abnormalities)

  • Presence of foreign cells (pus cells)

  • % Normal sperm

Body condition and fitness - rams should not be over conditioned in the run-up to the mating season. It is especially important that the condition of rams purchased at auctions is gradually adjusted to be no more than 3.5 to a maximum of 4 at the start of the mating season. Rams must also be physically fit (trained) - especially important where rams are kept in small camps and then have to do their work in large camps during the mating season. Start with a 10-minute walk and gradually increase the time until they are walking briskly for 30 to 45 minutes per day. During the walking sessions, rams can also be monitored for hoof, pastern and joint problems.

Ewes

In ewes, we need to make sure that the ewe’s teats and udder are functional. It will not help the ewe get pregnant, but struggle to effectively raise a lamb or lambs. If a teat is damaged and the udder (or even just one half) is hard or contains lumps, the ewe should not be mated.

Also make sure that the ewe's vulva does not contain growths/cancer that could adversely affect the mating process. Signs of the presence of “peester” disease can also be observed at the vulva and must be treated early (long-acting antibiotics).