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RESEARCH – for May. 16, 2011

Trichomoniasis (trich) and bovine genital campylobacteriosis (vibrio) both cause early abortions, infertility, and a long calving season. If repeat breeders aren’t noticed during the breeding season, the first sign of these venereal diseases may be a high percentage of open and late cows at pregnancy checking in fall. These diseases are very costly in terms of a lower calving percentage, lighter weaning weights, and a less uniform calf crop.

On rare occasions, a young breeding bull might clear a vibrio or trich infection, but most young bulls or bulls three to four years old or older will be infected for life. Most cows can clear a trich or vibrio infection within a few months, but some cows remain infected long enough to carry the disease into the next breeding season. Immunity to trich and vibrio is relatively short lived, so an infection or vaccination in one year may not protect animals in the next breeding season.

Treating trich or vibrio infections is generally not economical or effective because neither disease organism lives in the animal’s bloodstream. This makes it difficult for antibiotics to reach the parasite. Working antibiotics into a bull’s penis three days in a row is also not for the faint of heart.

The risk of transmitting trich or vibrio is higher when animals from different herds are commingled. As a result, community pasture groups need to allow the management team to implement and enforce biosecurity policies that help avoid these diseases. These include testing and culling infected herd and patron bulls and accepting only virgin heifers and cows with a calf at foot into the pasture.

In the spring of 2010, Drs. Cheryl Waldner, Steve Hendrick and Leanne Van De Weyer at the University of Saskatchewan’s Western College of Veterinary Medicine completed a study supported by Alberta Beef Producers. They followed cows from 40 herds that were exposed to 232 mature bulls on five Saskatchewan PFRA pastures. In response to past conception rate problems, these five pastures ensured that all mature bulls had a satisfactory semen test, were vaccinated against BVDV, IBR and vibrio, tested negative for (did not have) trich and vibrio before the breeding season started, and only allowed cows with a calf at foot to enter these pastures. Most (83 per cent) of these cow herds had also been vaccinated against BVDV and IBR, 65 per cent were vaccinated for vibrio, and 45 per cent were vaccinated against leptospirosis. At the end of the breeding season, 93 per cent of the cows were pregnant. Some of the breeding bulls were retested for trich and vibrio again at the end of the breeding season, and all were still free of both diseases. This illustrates that following recommended practices can help to avoid trich and vibrio.

The diagnostic tests for vibrio and trich are not ideal. Culture tests using smegma samples collected from the bull’s sheath are quite effective for detecting trich. However, confidently concluding that a bull does not have trich often requires three negative tests collected a week apart, with no breeding in between. Vibrio is even more difficult to culture. Vibrio dies if it dries out or is exposed too much to air, heat or cold. Dead microbes don’t grow in culture, so a culture test may fail to identify infected animals (this is known as a false negative). Antibody tests do not work very well for vibrio either, because cattle may carry a kind of campylobacter in their digestive tract that does not cause abortion, but can produce a “false positive” vibrio diagnosis.

DNA-based diagnostic tests are becoming commercially available. Both live and dead organisms have DNA, so these diseases can still be diagnosed even when the microbe has died before reaching the lab.

Drs. Hendrick and Waldner are now being funded by the Beef Science Cluster to evaluate the PCR tests for vibrio and trich. Three hundred bulls will be tested for trich using both the PCR and culture tests to see if the results agree. Diluted samples containing known numbers of trich will also be prepared to determine whether the PCR test can detect very low levels of trich. Samples from known vibrio-infected bulls and unexposed bulls will be tested using culture and PCR to determine how sensitive and specifithe PCR test is. If vibrio is there, will the test always find it, and does the test only find vibrio?

They are also studying whether “pooled samples” can be used to reduce lab costs. In this procedure, individual samples would still be collected from all bulls, but samples from five to ten bulls are mixed together and tested. If the test finds no disease, the entire group would be declared clean. If the pooled sample is infected, leftover material from each individual sample could be tested to determine which bull(s) from the pool are infected. This study will be completed in 2012.

ReynoldBergenistheScienceDirectorfortheBeefCattle ResearchCouncil.AportionoftheNationalcheckoffis directedtotheBCRCtofundresearchanddevelopment activitiestoimprovethecompetitivenessandsustainabilityof Canada’sbeefindustry.

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Following recommended practices can help to avoid trich and vibrio

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Dr. Reynold Bergen is the science director of the Beef Cattle Research Council.

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