Reader Asks About Culling Decisions and Trich
May 17, 2010
By Dan Goehl, DVM
Last fall we preg-checked our cows and 10% were open. We had the bulls checked and one bull checked out positive for trich. So we rechecked the other bulls two more times and and test results were all negative. We sold the bull that proved positive. This spring we are finished calving and another 10% of the cows that preg checked with a calf did not have one. The cows have not been with a bull for over 200 days now. My first question is: Can we keep the open cows and rebreed them or should we sell them? If we do keep them and breed them, can we use the same bulls on the cows that calved, or should not do this?
Trich can be a devastating problem to have in a herd. Often it can lead to problems much larger then you are describing. Luckily it sounds like you and your veterinarian have found the problem and are working to address it. The decision on culling versus keeping the bulls needs to be weighted on the value of the bulls to some extent. No matter how accurate a testing method is there is always a chance of a false negative. That is, an animal that truly is infected has a test result that shows he does not have the disease being tested for. The only way to be absolutely sure that your bulls are not carriers is to use virgin bulls.
Currently we use the PCR test for screening of bulls. This testing method is more accurate than the culture test of the past but because you have already diagnosed Trich in your herd I would check each bull at least twice. If the bulls test negative then it is most likely ok to keep them and use them.
Cows that have been infected with Trich clear the infection and should not be carriers. It would be wise if you decide to keep the open cows to have them palpated for breeding soundness to determine for sure none of the cows are carrying a uterine infection (pyometra). The decision to keep these cows also needs to be weighted on the value of the cows versus the cost of replacement. With current market conditions for slaughter cows being high, it might be more economical to sell these animals and replace them with new animals. You could also do a pregnancy palpation recheck to determine loss of pregnancy pre calving.
One last thought. You might consider using timed AI on your herd. This will insure that if for some reason the disease slips past all of our safeguards you would still have a high percentage of your cows bred early in the season. With a successful timed AI program you should be able to obtain 60% conception on AI. This gains some huge economical and management advantages that will pay for the process and as an extra bonus you will know the cows that are bred AI are not exposed to Trich.
Dan Goehl, DVM, and his wife own and operate Canton Veterinary Clinic in Canton, MO, where Dan works primarily with stocker and cow/calf beef operations. Dan is also partner in Professional Beef Services, LLC, which offers herd consultation and helps in data management and marketing of beef cattle.
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