Cattle raisers only use five of these classes in feeds. They are tetracyclines, neomycin, sulfas, macrolides and streptogramins.
In the tetracycline class, chlortetracycline (CTC/Aureomycin) and oxytetracycline (Terramycin) are commonly used for cattle. In the aminoglycoside class, neomycin is approved for use in combination with oxytetracycline (Neo-Terramycin).
While there is a recent approval for the macrolide tilmicosin (Pulmotil) use in the feed, tylosin is by far the macrolide class commonly used in cattle feed.
Aureo S 700 is perhaps the most recognizable name of a cattle feed additive. Aureo S 700, sometimes referred to as AS700, is a combination feed antibiotic and feed additive containing both chlortetracycline and sulfamethazine. The last class of antibiotics affected are the streptogramins. Virginiamycin (V-Max) is the only antibiotic in this class that impact cattle raisers.
The VFD regulations will remove all uses not associated with disease treatment, prevention or control. Therefore, all uses for growth promotion, improved feed efficiency or maintaining gain and feed efficiency during a disease event will be removed.
An important addition to VFD regulations is the requirement for a veterinary “order” for use. This means a veterinarian must approve the use, and the veterinarian must have a veterinary-client-patient relationship (VCPR) with the cattle raiser.
Additionally, the veterinarian must be licensed to practice in the state in which the cattle reside. All VFD orders will have an expiration date. The longest expiration date the FDA will approve is 180 days.
Tetracyclines
Chlortetracycline and oxytetracycline both have approvals for treatment and control of diseases that impact cattle. Both antibiotics are available for feed delivery to treat enteritis/scours caused by chlortetracycline- or oxytetracycline-susceptible Escherichia coli (E. coli) organisms.
These two antibiotics are available for feed delivery to treat bacterial pneumonia caused by chlortetracycline- or oxytetracycline-susceptible Pasteurella multocida organisms.
The approved dose for treating pneumonia and enteritis is 10 milligrams per pound per day for up to five days. The chlortetracycline dose for control of the P. multocida pneumonia is 350 milligrams per head per day.
Oxytetracycline is currently approved for prevention and treatment of the early stages of shipping fever complex (feed three to five days before and after arrival in feedlots) when dosed at 0.5 to 2 grams per head per day.
However, the VFD regulations indicate a causative bacteria must be indicated. Unless the sponsoring companies add a named causative bacteria to their label indications, there is a possibility of losing this labeled use and dose.
A chlortetracycline dose of 350 milligrams per head per day is approved for control of Anaplasma marginale in cattle less than 700 pounds, and the dose for control of anaplasmosis in beef cattle and non-lactating dairy cattle greater than 700 pounds is 0.5 to 2 grams per head per day.
Additionally, 70 and 75 milligrams per head per day is approved for chlortetracycline and oxytetracycline, respectively, to reduce (control) liver abscesses in cattle greater than 400 pounds.
Sulfas
Sulfamethazine is currently approved to be fed with chlortetracycline. The combination product is Aureo S 700. Aureo S 700 is labeled to provide 350 milligrams of chlortetracycline and 350 milligrams of sulfamethazine per animal per day. The label indicates it is to be fed for 28 days and has a seven-day withdrawal.
The use indication is for maintenance of weight gains in the presence of respiratory disease. Currently, there are no disease treatment, prevention or control indications for this product, and therefore Aureo S 700 will not be available after Jan. 1, 2017.
Aminoglycosides
Neomycin is the only antibiotic in the aminoglycoside class approved for use in cattle. It is approved for use in combination with oxytetracycline, and the combination feed additive contains equal concentrations of both antibiotics.
Except for not having an approved use for control of liver abscesses, the indications for use and the dose approved for use are identical to the indications and dose approvals for the tetracyclines discussed above. There is a five-day withdrawal required for this neomycin-oxytetracycline feed additive.
Macrolides
Tylosin is the most common macrolide feed additive cattle raisers are familiar with using. The product label includes use for reduction (control) of liver abscess in cattle caused by Fusobacterium necrophorum and Trueperella (Arcanobacterium) pyogenes.
The approved dose of tylosin is 60 to 90 milligrams per head per day, which should be mixed as 8 to 10 grams per ton (90 percent DMB). While Fusobacterium necrophorum is the causative organism in bovine foot rot, tylosin is not approved for use to treat, prevent or control this condition.
Since the VFD regulations were announced, the feed use for tilmicosin to control bovine respiratory disease was approved by the FDA. Most cattle raisers know tilmicosin as Micotil.
The tilmicosin feed additive is named Pulmotil. There are a number of restrictions associated with its use. First is that 10 percent of the cattle in the group must have respiratory disease. A veterinarian is not required to be the person confirming 10 percent of the cattle are sick.
Second, the 14-day treatment can only be fed during the first 45 days on-feed. Third, it must be fed in a complete feed with no other feedstuffs available. This includes free-choice hay or lick tubes. Fourth, it must be the only macrolide that has been or is being used.
Fifth, the VFD order is only effective for 45 days. The dose is 5.68 milligrams per pound, and the antibiotic feed additive is available in a 5.68-gram-per-pound premix. This makes the product relatively simple to use, as 1 pound of premix will treat 1,000 pounds of cattle.
Therefore, a 50,000-pound semi-load of 5-hundredweight cattle would get 50 pounds of premix per day or 700 pounds of premix for the entire 14-day treatment. Tilmicosin feed additive has a 28-day withdrawal.
Streptogramins
Virginiamycin is the only streptogramin approved for use in cattle to reduce (control) liver abscesses. The approved dose is 85 to 240 milligrams per head per day to be mixed as a 13.5- to 16-gram-per-ton feed.
Critical note
It is critical to understand that FDA-approved feed additives cannot be used other than as labeled, which means these feed products must be fed exactly as instructed on the label.
This includes reason for using the product, dose per animal, number of days fed and observe indicated withdrawal times. 
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Dee Griffin
- Veterinarian, Professor
- Texas A&M University, College of Veterinary Medicine, Canyon, Texas
- Email Dee Griffin
