Vet’s Voice: Herd biosecurity measures
June 29, 2012
Hopefully everyone received a late June rain to replenish those missed during May and early June. In our area, it looks like the grass will come back a bit and the row crops appear to be growing rapidly. With a few more timely rains (and no hail), we should get a harvest.
Because of low cow numbers in the past, many producers may be adding cows or heifers to the herd. A good biosecurity program is needed to avoid bringing problems into the herd.
Many producers have purchased open, young cows (heifers and heiferettes). In recent years, South Dakota has seen an increase in trichomoniasis (or “trich”), a protozoal disease which decreases pregnancy rate by 25-30 percent. The disease is carried in an open female whose pregnancy has been terminated due to infection; or being exposed to a bull which can transfer the disease from cow to cow as they are bred. In response to increased reports of trich, the Animal Industry Board passed the following regulations:
• No open females may be purchased unless they have a calf at side
• No non-virgin bulls may enter a herd without a trich test.
This keeps the devastating disease from being brought into the herd from an infected bull, or a female that aborted its calf and remains a carrier. If females are purchased bred 150 days or less, it is best to separate them from the rest of the herd. These short-gestation females may be exposed to trich and could abort later. Segregation will keep the disease from being shed to the primary herd.
Bovine viral diarrhea (BVD) is another disease which can easily be carried into the herd. We recommend testing bulls and herd replacements to keep permanently infected (PI) animals from entering the herd. These PIs shed BVD virus in the herd constantly. This live virus causes infertility, abortions, weak calves and post-birth calf infections. An animal that tests PI-negative will never become a PI.
A good vaccination program keeps health problems to a minimum. Infectious Bovine Rhinotracheitis (IBR) was once the most common cause of abortion storms in South Dakota. This problem has been minimized through good vaccination programs using live virus vaccines.
Usually leptospirosis (or “lepto”) is administered with other vaccines. I have not seen a laboratory-confirmed lepto diagnosis in the area for about 20 years. Common leptos usually cause late-term abortions or weak calves. In recent years, lepto hardjo-bovis has become an issue in our area. This organism causes early-term abortions which appear as infertility – females come back into heat several months after breeding. This problem often happens in pastures with dugouts or other water sources that tend to become stagnant. New vaccines and management protocols can minimize these problems.
Be sure to remove all external and internal parasites before adding animals to the herd. These new animals can easily contaminate pastures with parasites. In turn, this causes the herd to need more feed to nourish the parasite load they picked-up from their new herd mates.
Consult with a veterinarian, extension specialist, or nutritionist to develop a biosecurity program for your herd. Careful understanding of state regulations, a good vaccination program, testing for selected diseases, and a good parasite management program will keep the herd highly productive during expansion of the herd. Always remember, “good fences make good neighbors.”
Dave Barz is a veterinarian at Northwest Veterinary Supply in Parkston, SD.