Keeping stocker calves healthy, or preventing them from succumbing to bovine respiratory disease (BRD) to begin with, isn't easy or cheap. But the alternative obviously can be worse.
In fact, with the high value of stocker calves today, John Currin and Dee Whittier, Virginia-Maryland Regional College of Veterinary Medicine Extension veterinarians, explain metaphylaxis is usually worthwhile if more than 25% of a group of calves is expected to get sick. That's based on risk factors of incoming calves for BRD, such as: Source of cattle (weekly vs. special sales vs. on farm sales)
Vaccination, deworming history of cattle
Commingled vs. single-source cattle
Age/size of the cattle
Sex of the cattle (bulls vs. steers)
Time of the year (spring vs. fall)
Weaned vs. unweaned
Your ability to detect and treat sick calves
Your history of BRD
Comfort of your adjustment facilities
Value of the cattle (not a risk factor but important in the decision to use metaphylaxsis) Though every situation is different, Currin and Whittier say the 25% level is a useful rule of thumb despite the fact national averages for applying the strategy to a 5-weight calf range from $4.05-$18.15/head depending on which of the five products approved for metaphylactic use are utilized.
Conversely, these veterinarians advise using mass medication --treating all calves in a group once individual treatment no longer makes much economic sense -- when 10% of the calves have been treated for three consecutive days, or when more than 25% of the calves require treatment on a single day.
"While not perfect, using these rules of thumb will help make careful decisions, instead of reacting in the heat of the moment or failing to consider this option until after 60-80% of the calves have been treated," they say.
Incidentally, Currin and Whittier offer four reasons for the fact the same percentage of cattle get BRD as 40 years ago, even though knowledge, vaccine technology and antibiotic variety have increased substantially in the same period of time: A 500-lb. calf now is much younger than it was 40 years ago.
A 500-lb. calf is less likely to have been weaned now than 40 years ago.
Stocker producers are more likely to buy cattle every week as opposed to a major group buy or two 40 years ago.
Stocker businesses are larger operations than 40 years ago. You can find more info from Currin and Whittier about "Strategic Use of Antibiotics in Stocker Cattle" at: www.ext.vt.edu/news/periodicals/livestock/aps-06_04/aps-315.html.