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Ewe Reproduction

Ewe Mating PerformanceBetween 3% and 5% of sheep flocks in New Zealand will experience an abortion outbreak in any one year. 


While some farms may only experience a low level of ewes aborting, the cost of losing even a few pregnancies, and feeding unproductive ewes quickly adds up when lamb values are high.  Moreover, the introduction of an infectious agent in unvaccinated susceptible flocks can result in losses as high as 30%. 

Campylobacteriosis is the most commonly diagnosed cause of infectious abortion in ewes in New Zealand.  Campylobacter infection causes abortions most commonly during the last six weeks of pregnancy and can also result in the birth of weak lambs leading to high peri-natal lamb losses. Infection is spread via contact with aborted foetuses, afterbirth, or contaminated feed and water. After abortion, some ewes may remain intestinal carriers and continue to act as a source of infection.   Vaccination is an effective tool to prevent abortion losses due to campylobacter.  Sheep that have never been vaccinated, regardless of age, will need two vaccinations 4 - 6 weeks apart. Annual boosters are recommended thereafter.

Toxoplasmosis can result in foetal death at any stage in pregnancy. Infection during early stages of pregnancy may result in resorption of the foetus and no outward sign of abortion.  This can make recognition of a problem related to toxoplasma infection difficult to identify. 

The great news is that ‘Toxovax®’ is a highly effective vaccine only required once in a ewe’s lifetime.  Something to bear in mind is that ‘Toxovax®’ is a ‘made-to-order’ live vaccine. Once manufactured it only has a 10-day shelf-life and must be refrigerated at all times while not in use.  This means planning and placing orders well in advance.  Being prepared with chilly bins and ice packs for transport and handling is also essential.  Toxoplasma gondii can also cause illness in people. While most healthy adults are unlikely to have a problem, anybody who is immune compromised and pregnant women should not handle ‘Toxovax®’.