Trichomoniasis (trich) is a sexually transmitted disease that can devastate a herd's conception rate and profitability. There's no treatment for trich infection in bulls or cows, and many states specifically regulate the sale, purchase and transport of non-virgin bulls and testing procedures for shared grazing situations.
Bulls three years and older are the primary carriers, but they typically show no outward symptoms. Virgin bulls are considered safe as the disease must be transmitted from an infected cow to the bull.
The infected bull transmits trich to the cow during breeding; as a result, the cow will abort within 60-120 days. Infertility can last for 2-6 months at which time most cows clear the infection.
The first indication of infection is typically an increased number of cows cycling at the end of the breeding season. Trich infections can be confirmed when pregnancy-checking. Infected herds will have an increased number of open cows, sometimes 20-40% of the cowherd. Open cows should be culled.
In a modeling experiment, University of California veterinary researchers evaluated vaccination, annual bull testing, shared grazing, bull age and herd size on calving incidence in herds known to be or previously infected with trich. They found:
- Annual testing of all bulls within a herd and culling bulls with positive culture results prior to the start of the breeding season was most effective in increasing calving incidence and annual income.
- Vaccination was a valuable alternative to increase calving incidence when the risk factors such as not testing and use of shared grazing could not be avoided.
- Larger herds were at greater risk of decreased calving than smaller herds.
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-- Scott Laudert