Using the information
Sanderson and Smith spent two years developing the models and another year to get them programmed and implemented on the Web. “We did an extensive review of the scientific literature to identify all the available data on BVDV and trich,” he says. “We also surveyed some experts on areas where there was not much scientific literature. This defined the factors we wanted to model and the values that go into the model to make it work.”
He suggests the best way for a veterinarian to use these models with clients is to sit down with him/her and fill in the information as accurately as they can. “The veterinarian helping the producer input good numbers and interpret results is essential,” he notes. “I think it could also be a great way to start some discussion on risks and overall herd health.”
At the top of the results page is a probability of introducing BVDV (or trich) in your management scenario if you do nothing to prevent it, Sanderson says. That by itself is not a very useful number. “The point of the model is to identify what are the most effective and economical control strategies to minimize the economic risk of disease introduction.”
The set of numbers below show the probabilities of exceeding the reported dollar value in costs (for BVDV and a 300-cow herd they are reported for three levels: $30,000, $21,000 and $15,000) for each of the control strategies listed. “This lets the producer decide how much financial risk they are willing to take; sometimes the optimal strategy is different for different loss levels.” So for the example given here, a 300 cow herd imported 50 pregnant heifers and three bulls each year and shared a fenceline with one other herd during breeding. “This results in a 99% chance of importing BVDV over 10 years if no control is practiced,” Sanderson says. The control strategy that gives the lowest probability of exceeding $30,000 in costs is to vaccinate all breeding stock and test all imported cattle, including the calves of pregnant imports.
The model identifies the strategy or strategies with the lowest probability of exceeding the loss at each level and tags it with a “Best Choice” label. “If the model says you should vaccinate and test all imports, it’s because that strategy has the lowest probability of exceeding the designated cost,” Sanderson explains. The costs associated with each control strategy also include all costs associated with testing, labor, vaccination, etc. The model is meant to provide decision support for choosing the most economical testing and vaccination control strategy for a producer’s management.