In regard to your April article “Tracking Trich,” (page 30), I practice in a mixed animal practice in northeast California that includes many large ranches that run in California, Oregon and Nevada and run on public lands in the summer.
Our practice diagnosed heavy trich infections in 1980 and have seen many cycles ever since in this area. We usually see 35% non-pregnant cowherds with 5-10% infected bulls. In heavily infected herds where the herd had been clean, we might see 50% open cows and 50% of the bull herd infected.
A few years ago, we had an infected herd with 35% of the cows open and 25% of the bulls infected. The following year, we noted 35% of the cows open and no infected bulls. This herd had no trich vaccine program and was poorly managed. We felt that the bulls were being chronically infected with trich and were building immunity in the field.
Even though past trials run by Dr. Bill Kvasnicka did not show the vaccine to be highly protective in bulls, we decided this immunity from vaccine might be slower in giving local protection in the sheath. We now recommend vaccinating all bulls with one dose of vaccine two to six weeks apart with boosters every six months.
In the past four years, we have diagnosed very few bulls positive for trich that have been on a good vaccine program. A much higher pregnancy rate has also occurred at this time. This may keep us from feeling the need to sell good bulls more than four years old.
Cattle herds in which trich is at risk are treated similarly for the cows. We recommend two separate vaccinations on females two to six weeks apart with an annual booster prior to breeding. If the calving period is spread out or fall and spring calving cows are run together, we recommend vaccinating females in the spring and again in the fall.
Donald D. Crum, DVM
It's A Hoof, Not A Foot
In your May issue (cover, cover story and “Editor's Roundup”), you mention foot-and-mouth disease (FMD). Please be aware that the correct name for the disease is hoof-and-mouth. FMD is the name provided by animal rights people and implies contagion to humans.
San Rafael, CA
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