Have you ever guessed the weight of a Bantie rooster and missed it by about 10 lbs.? Turns out that dosages for treating cattle with pharmaceuticals are just as far off when they're based on group averages and eyeball guesses rather than the actual weights of individual animals.

In fact, according to a recent Kansas State University (KSU) study, unless pharmaceutical dosages — as opposed to vaccines that aren't weight-dependent — are based on individual weight, about half the cattle are either under-dosed or over-dosed.

Specifically, the study indicates that using average lot weight to determine dosage levels for metaphylactic antimicrobial treatment and anthelmintic treatment of stocker and feeder cattle (Table 1) meant that more than 20% of the cattle treated were under-dosed by 10% or more.

“Under-dosing with these classes of products has the potential to result in far greater economic losses than the expense of excess product cost typically associated with overdosing,” explains Larry Hollis, DVM, a KSU beef Extension veterinarian. “Anything within 5% is regarded as normal error. Anything beyond that can be biologically significant.”

As an example, Hollis points out cattle under-dosed with anthelmintics may still carry a significant worm burden, reducing performance. Likewise, under-dosing antimicrobials can lead to poor treatment response resulting in increased re-pulls, chronics and mortality.

On the flip-side, Hollis explains, “Over-dosing lighter weight animals may lead to toxicity problems or require extended withdrawal times prior to harvest.” Never mind the fact that any use of these products outside of FDA-approved recommendations represents extra-label use.

Hollis says the specific relationship between accurate dosage and product efficacy varies between products. As a result, the specific cost of over-dosing and under-dosing is inestimable without massive product-by-product population studies.

But the industry does have some industry-wide notion of what management and product failure can cost. Texas A&M University Ranch to Rail data corroborates the high cost of repulls.

Data indicates that cattle treated even once were worth $80.12 to $151.18 less in net return than those that remained healthy. More specifically, each time cattle had to be pulled they were less likely to perform as well as pen mates, costing more and earning less along the way (Table 2).

For perspective, only 25% of feedlots responding to the most recent National Animal Health Monitoring Service (NAHMS) feedlot survey said they always record cattle weight at the time of treatment. Meanwhile, 56.2% said they never record the weight. It's rational to assume individual weights aren't recorded because the cattle haven't been weighed.

Hollis believes the initial industry snapshot provided by the KSU study should heighten industry awareness about the opportunity to increase cattle performance and response to pharmaceutical products. If producers weigh animals individually and dose them accordingly, Hollis says, “You still spend the same amount of money on product, but you spend it where it's needed.”

Table 2. The effect of number of BRD treatments on feedlot performance and carcass quality of fed cattle
No. of hospital pen visits 0 1 2 3 4
Total % 81 14.2 3.3 1.0 0.4
% deads 0.9 2.9 7.2 10.0 16.0
% railers 0.2 1.0 6.0 8.0 16.0
Medicine cost ($) 0 16.96 33.63 53.39 69.79
ADG (lbs.) 2.92 2.77 2.57 2.45 1.99
% Choice 41 25 22 17 18
% Select 53 61 57 72 45
% Standard 6 14 21 11 37
Source: Texas A&M University Ranch to rail data, 1997-1999

But what's that truly worth, relative to the added costs associated with weighing cattle individually? In the absence of studies assessing the direct cost product-by-product as mentioned earlier, logic says the economic differences between being right and merely close can be substantial.

As Hollis says, “Given the differences between products, we don't know exactly what under-dosing and over-dosing stocker and feeder cattle costs, but do you?”

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