Sheep breeding
Managing ovine brucellosis to maximise ram fertility

Ken Wilson and Nancy Ollerenshaw, formerly of the Agency for Food and Fibre Sciences
Revised by Deborah Maxwell and Nicole McLennan, Agency for Food and Fibre Sciences

Key points

• Ovine brucellosis is a common infectious disease that can affect the productivity of ram flocks.
• Brucellosis is found in most commercial ram flocks, however it can be easily managed by adopting a few simple ram husbandry procedures.
• Rams should be palpated and culled annually for testicular abnormalities. Joining percentages and joining length need to be adequate.
• Most studs are accredited free from brucellosis, however you should ask about the stud's current status or brucellosis policy if unsure.

Effects on fertility

Ovine brucellosis is caused by the bacterium Brucella ovis. These bacteria cause an infectious swelling in the epididymis (duct that conveys sperm from the testes), 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.

The effect of brucellosis on whole flock fertility is usually negligible providing:

• rams are examined at least once a year and those with palpable abnormalities are culled
• joining percentages and joining length are adequate.

This is because healthy, fertile rams will compensate for lower fertility brucellosis-affected rams.

Note: Brucellosis can establish in the uterus of a pregnant ewe, however it is only carried for the term of that pregnancy. The bacteria can cause abortion, but more commonly results in the birth of small, weak lambs.

Method of spread

Brucellosis is spread when infected rams 'ride' other rams (more common in younger rams), and rams mate with ewes that have been previously served by infected rams.

Commercial flock management

In a young ram flock (up to six years of age) less than five per cent of rams are usually culled for epididymitis each year. This can climb to ten per cent or more in older flocks because the incidence of brucellosis increases with age.

However, rams of all ages are susceptible and sheep breeders who continually have to cull young rams with epididymitis should consider keeping replacement rams separate from older rams for up to 12 months (although they can be mixed for joining).

Young rams have an increased tendency to ‘ride' other rams, which can result in the rapid spread of brucellosis if it is present in the older ram flock.

The process required to completely eradicate the disease is long, expensive and not totally foolproof, and in most commercial flocks, not economically justified.

Regular palpation of rams will ensure the disease remains at a manageable level that does not affect fertility and productivity. When palpating rams, start as high up in the cords as possible and gently squeeze the testes through your hands, feeling the top, body and tail for any lumps. Both testicles should be the same size, smooth and firm. All rams with testicular abnormalities should be culled, destroyed or removed from the property.

Introduced rams and newly purchased rams should be palpated on arrival and kept separate, if possible, for 8 to 12 weeks to allow any infected rams to show detectable lesions.

Rams should always be on their own between joining and all stags should be culled as they may carry brucellosis.

Stud management

Most studs have entered into a voluntary Ovine Brucellosis Accreditation Program and have reduced the incidence of brucellosis in their stud flocks to non-detectable levels. If you are unsure about your stud’s current status or brucellosis policy, ask about it when next purchasing rams.

Acknowledgment

The Lamb Boost Project funded by Australian Wool Innovation produced these notes.

Further information

For further information contact the DPI Call Centre on 13 25 23 (Queensland residents) or (07) 3404 6999 (non-Queensland residents) between 8 am and 6 pm weekdays, or e-mail callweb@dpi.qld.gov.au.

This DPI Note is also published on the DPI's PrimeNotes CD-ROM.

Information contained in this publication is provided as general advice only. For application to specific circumstances, professional advice should be sought. The Department of Primary Industries Queensland has taken all reasonable steps to ensure the information in this publication is accurate at the time of publication. Readers should ensure that they make appropriate inquiries to determine whether new information is available on the particular subject matter.