Kansas State University Extension veterinarian Dan Thomson outlined an “evidence-based approach” to starting calves during last month’s K-State Beef Stocker Field Day.
During high-mortality episodes, Thomson says producers should consider several factors in determining strategies for solving the problem. One is morbidity rates, or the percentage of sick cattle. Another is the case-fatality rate, meaning the number of treated cattle that die, which could indicate whether or not the drug is working.
He notes that a high mortality rate alone does not necessarily mean the treatment failed. He presents a scenario in which a producer had 1 percent death loss last year and this year he had a 5 percent death loss. The producer wants to change drugs or veterinarian. But, Thomson says, if last year the producer and his veterinarian pulled 10 percent of the population and this year pulled 50 percent of the population, the case fatality rate was the same in both years — 10 percent. The treatment, he says, worked the same this year as it did last year. The problem is the high morbidity rate.
So what caused the higher morbidity? Thomson says a number of factors could be at play, including the source of the cattle, viral antigens, weather, people, prior nutrition, transportation or the “evenness” of the cattle.
Timing of cattle flow is a key factor, and the period when a stocker operation or feedyard brings in multiple groups of cattle naturally presents elevated risk. And, he adds, the more new high-risk cattle you have at a facility the higher risk your low-risk cattle become.
Researchers at K-State recently completed a survey of 23 feedlot consulting veterinarians, asking about animal-health issues. As a group, these veterinarians supply consultation for more than 11 million head of feeder cattle annually and average nearly 5 million head per individual.
The survey asked veterinarians what they believe is the most important factor for predicting feedlot morbidity or mortality, and on average, they listed the factors in the following order:
- Cattle health risk
- Weather patterns
- Receiving nutrition program
- Amount and quality of labor
- Class of antibiotic use for metaphylaxis
- Class of antibiotic use for treatment
- Brand of vaccine
Following are the rates at which these veterinarians recommend specific types of vaccines:
|High-risk calves||Low-risk calves|
|BVD Type 1||100%||95.6%|
|BVD Type 2||100%||95.6%|
Read more of Thomson’s presentation.