Dairy farmers should think of biosecurity and surveillance activities on their farm as "protecting what you have," says dairy veterinarian Dr. Bob Steiner.
Outside sources — purchased animals, vendors, truckers, vectors, wild animals and even veterinarians and their trucks — can bring in things that might be harmful to the dairy herd. It's helpful to the productiveness of the dairy if managers give some thought to those concerns.
Steiner, one of the bovine practitioners with Lodi Veterinary Care, spoke to a group of dairy farmers recently at a meeting in Roxbury.
One of his suggestions for the farmers was that if new animals are being brought into a herd they should be tested for diseases like bovine viral diarrhea (BVD) and Johne's disease.
"Every couple of years we get into an outbreak of BVD and it can be devastating," he said.
Because there are animals that can be "persistently infected," as the scientists call them, it can be difficult to vaccinate out of the problem. The calves carried by these persistently infected animals can carry the disease forward in the herd, he added.
Steiner suggested farmers try to buy new animals from reputable sources, which may be a person or dealer they have dealt with in the past and have had good luck with.
These reputable sources might be another dairy farm where there is the possibility of looking at herd records like cull rates, somatic cell counts and death rates, Steiner said, which will all help the buyer with future biosecurity concerns.
It makes sense for dairy managers to also try to keep track of endemic diseases in their herds – those that are always present but which may be under the radar because they are at low levels.
Respiratory diseases can be carried forward in the herd by "carriers, shedders and sickies," he added.
Especially in the calf barn there can be a "day care effect," with one sick calf exposing others to some pathogen or illness. "You know how your kids get sick at day care and you have to pick them up at the curb so they don't infect the other kids. It can be like that in groups of calves."
What he called "inside sources" of disease problems can come from incorrectly feeding colostrum to calves. Feeding the proper amount of colostrum at the right time to calves "is probably the most important single thing you can do for the animal in its entire life."
Getting calves off with good levels of colostrum and immunity antibodies means that they will produce better and perform better as adults.
"It limits risk," he said. "I look at is as insurance — limiting your risk with good husbandry and vaccination." He looks at colostrum as something akin to vaccination for the baby calf and something that will carry forward health effects throughout her life.
Another way to ensure biosecurity, he said, is to spot check levels of disease in the dairy herd with various tests.
A pooled sample from the bulk tank can be used to do PCR tests for various pathogens and can be fairly economical to do because the sample is pooled and the tests are getting more inexpensive.
Bulk tank samples taken every quarter, every month or every two weeks are a good way to keep track of problems that could be on the rise in the milk, like staph aureus or strep ag, he said.
Bulk sampling of ear notches taken from animals, can also be used to screen the herd for BVD to get an idea of whether or not this is a problem in the herd. While it's not done too frequently, Steiner said farmers can also do premises tests of Johne's disease by taking samples from the manure pit or holding area.
Another potentially helpful tool is to have veterinarians do post-mortem exams on dead fetuses and placentas from spontaneous abortions in the herd to determine what may have caused them. "This can be a chance to learn something and perhaps head off a potential problem in the herd.
"Negative news can be good news, if we don't find anything. But the post-mortem exam may point the way to actions that can improve herd health or confirm a diagnosis."
Other animals that die on the farm can provide clues to improve herd health as well. An exam can show if certain kinds of pneumonia are present or if antibiotic treatments are not working.
"We can learn a lot from these animals."