If your water medication doesn't seem to be doing its job, it may not be the product's fault.

It's disappointing, and expensive, when you treat animals with an approved antibiotic and it fails to produce the desired results.

The problem may be due to any of several causes. As the first step in nailing it down, ask your veterinarian to answer the following five questions:

1. Is the infecting agent a virus or bacteria? If it's a viral infection, antibiotics won't help. Another treatment is required – perhaps injecting an appropriate vaccine based on the diagnosis and which product best fits the problem.

2. If bacteria are the problem, did the veterinarian test the bacteria to determine the sensitivity to various antibiotics? Has the strain developed resistance to the antibiotic you're using?

3. Was the medicated solution the animals' only water source, or did they have other water options?

4. Was the dosage level too low? It makes no difference whether a low dosage occurred because of a miscalculation or as an attempt to save money, medication concentration in water must not drop below the recommended levels.

"Each antibiotic has an approved dose range," points out Al Scheidt, president of the American Association of Swine Practitioners. "That is to say the highest approved dose and lowest. Perhaps the dose was too low and not strong enough. If so, you need to use a higher dose within the approved range."

5. Was the treatment period long enough? While you may see sick animals begin to improve in just a day, Scheidt notes, it takes two or three days to evaluate an antibiotic's effectiveness. It's important to stay with the regime.

As the next step, you need to answer questions about how the medication was used. The following points are based on Scheidt's 19 years of trouble-shooting experience with Purdue University and as a Pfizer Animal Health field service veterinarian.

  • Did the medication mix into the water thoroughly? It must blend completely for all animals to receive an effective level.
  • Is the medicator or proportioner working at the manufacturer's specified water-flow rate and water pressure? If in doubt, call the manufacturer to check.
  • Are the hogs too sick to drink? Any animals that are unable to get up to drink from a waterer need to be injected individually with a therapeutic level of an approved antibiotic.

"Only stronger, more dominant individuals may be able to consume enough medicated water," Scheidt notes, "Fever and general health influence water consumption."

Using these checklists, Scheidt says, you should be able to correct problems that prevent medications from working.

"If this doesn't work and animal condition does not improve," he says, "waste no time consulting with your veterinarian and switching to another treatment."


Water consumption varies with various factors: the animals' age, type of feed, environmental temperature, stage of lactation, fever, high urinary output or diarrhea. Veterinarian Al Sheidt provides these examples of daily intakes. If you don't know your herd's typical intake levels, this is at least a place to start.

PIG weight WATER weight Volume
13 lbs. 0.89 lbs.. 0.11 gal.
27 lbs.. 1.84 lbs.. 0.22 gal.
55 lbs.. 3.75 lbs.. 0.45 gal.
110 lbs.. 7.50 lbs.. 0.90 gal.
220 lbs.. 15.00 lbs.. 1.80 gal.
PIG weight WATER weight Volume
13 lbs. 2.61 lbs. 0.31 gal.
27 lbs. 5.39 lbs. 0.65 gal.
55 lbs. 10.99 lbs. 1.32 gal.
110 lbs. 21.98 lbs. 2.64 gal.
220 lbs. 43.95 lbs. 5.27 gal.

Source: Merck Veterinary manual, 8th Edition