Antibiotic dosages are determined by individual cattle bodyweight.
Zoetis defines “responsible use of antibiotics” as administering medication under the guidance of a veterinarian, following the directions on the approved product label and using only the amount needed to treat the problem. Therefore, we are using antibiotics responsibly only when we factor in appropriate dosage based on accurate, individual bodyweight.
Commonly, dairies determine antibiotic dosage based on visual estimates of weight for large and small cows. Generally speaking, a large cow is a large cow; however, this practice of “eyeballing” presents a big risk in under or overdosing of antibiotics, as doses vary greatly given differences in bodyweight.
For example, recommended antibiotic dosage differs for a 1,500-pound cow versus an 1,800-pound cow. Although first lactation cows should have fairly uniform bodyweights, we have seen more than a 600-pound difference in fresh heifer bodyweights on a dairy with a scale. The spread can be even greater with older cows.
The impact of under and overdosing antibiotics
Without capturing accurate, individual bodyweights, cattle may be underdosed, which can decrease antibiotic efficacy or create poor response to treatment. This can result in increased treatment and labor costs due to disease relapse. Even more, dairies may be at increased risk for residues if other antibiotics are introduced and FDA-mandated withdrawal times aren’t followed.
On the other hand, overdosing cows with antibiotics increases risk of violative residues in milk and meat and increases treatment costs, as more product than needed is being used. Keep in mind that overdosing isn’t just administering too much of a product – cows also can be overdosed based on volume of antibiotic administered per injection site.
What can you do?
1. Stop guessing.
2. Capture individual weights with a weight tape or digital cattle scale.
3. Weigh cows at freshening, one month post-calving and at dry-off to monitor for weight fluctuations that could indicate potential metabolic issues that may require treatment.
4. Follow product labels.
Through responsible use of antibiotics, we all can help maintain the effectiveness of these important resources. Accurate bodyweight data allows for more accurate antibiotic dosing, resulting in improved treatment efficacy and prevention of residues in milk and meat. Work with your local resources to have a discussion on how to build a more strategic plan on proper dosing of antibiotics. 
Richard Wallace is a veterinarian with over 25 year of dairy production medicine experience in clinical practice, academia, extension and industry.
—From Zoetis news release
PHOTO: Staff photo.
-
Richard Wallace
- Cattle & Equine Technical Services, Dairy
- Zoetis
- Email Richard Wallace
