Feed Lot Magazine Online, Trichomoniasis Can Drastically Decrease Calving Rates

Trichomoniasis is a disease that is largely misunderstood in the cow/calf industry, according to Dr. Steve Connell with Fort Dodge Animal Health. "A lot of people don't know much about the disease, and by the time it is diagnosed, their entire herd is infected with it."

Trichomoniasis is a venereal disease in cattle that causes reproductive failure and considerable economic loss in areas of the country where natural breeding is used, according to University of Nevada, Reno research. The disease results in infertility and causes early embryonic death, abortion and pyometra. "Trich," as it is often called, is usually diagnosed in a herd after a dramatic decrease in calving rates, says Connell.

"An infected cow will become pregnant, and as the fetus grows, the trich organism interferes with blood circulation in the uterus. Eventually, the fetus outgrows its blood supply and aborts," Connell explains.

"The majority of the abortions occur early enough in the development of the fetus that a rancher never notices," he says. In fact, most abortions occur during the first half of gestation, typically within 90 days.

The disease is spread by coitus with an infected animal. An infected bull does not show any obvious sign of infection and serves only as a carrier of the organism. Older bulls tend to become permanent carriers of the highly contagious disease. Research shows that when an infected bull was bred to virgin heifers, 95 percent of heifers were infected with the disease. Therefore, due to the contagious nature of the disease, identification of a single infected animal within the group implies total herd infection, according to Connell.

Infection in the cow does not provide many noticeable symptoms. Some cows develop a natural immunity and will conceive and carry a calf to term after three to five heat cycles following abortion. That immunity, however, is not permanent, and the cow is subject to reinfection in subsequent breeding periods.

To determine if a herd is infected with Trich, bulls are tested by obtaining cultures of the preputial (internal sheath) fluids. If infection is found, there is no treatment for the bulls, however the cows can be vaccinated with TrichGuard, manufactured by Fort Dodge Animal Health. It will take a few weeks for infected, vaccinated females to "clear" the vaginal infection.

The vaccination is most effective if administered 30 to 60 days prior to breeding season, Connell says. Initial vaccination of a cow herd requires two injections, 30 days apart. Subsequent vaccinations only require one dose. "The vaccine does not provide long-term immunity, therefore it is most effective if given prior to calving," he says. "Many cattlemen give the vaccine during pregnancy checking so that they don't have to gather the cow herd prior to breeding. Although that is easier, it is just not as effective."

Connell admits the vaccine is expensive, however many case studies have proven that the lost revenue of open cows far exceeds the cost of the vaccine.

"In 1992, a large cow/calf operation noticed a severe drop in calving percentages. Traditionally, they calved in the low 90s, but that year only 68 to 70 percent of their cows had calves," Connell says. "Trich was identified in 18 bulls, and an aggressive control program was instituted with TrichGuard. Calving rates improved dramatically in the next two years.

"However, due to the cost of the vaccine, it was discontinued in some of the herd. The following year, the untreated cows had pregnancy rates 4.2 percent lower than those vaccinated. This 4.2 percent difference translates to 86 "lost" calves. The revenue lost on those 86 calves comes to over $29,000!" Connell explains.

To prevent Trich from infecting a herd, Connell recommends using young bulls, selling bulls that are positive, testing newly purchased bulls, have fences in good repair, and do not use loaner or lease bulls.