Oral swine vaccines are gaining popularity in the nursery production phase. But when considering an oral vaccine, it’s important to understand the impact that a medication-free window can have on pig performance.

Kansas State University research shows that eliminating antibiotics from the nursery diet to provide a medication-free window to apply oral vaccines can actually diminish overall pig-growth performance and economic returns. Rethinking how and when oral vaccines are incorporated into a swine-health program could improve pork producers’ return on investment.

Specifically, producers may profit from forgoing vaccines during the nursery phase or shifting vaccine administration to a later or earlier production stage. Our trials illustrate that the return on investment from antibiotic use can vary depending on the active ingredient used. Also, there can be positive respiratory benefits and improved growth performance from using a combination of tiamulin and chlortetracycline in the nursery.

Although our studies demonstrate that the use of antibiotics for disease control does improve profitability, it’s also important to note that antibiotics help lower mortality and morbidity rates, and are one tool in providing sound care for nursery pigs.

Improving Performance through Increased Feed Intake

Historically, swine-health research has demonstrated that including antibiotics in nursery-pig diets can lead to improved pig-growth performance through enhanced disease control. The greatest positive response is normally through an increase in feed intake, which can improve average daily gain. Although the benefit of including feed-grade antibiotics in the nursery phase is well documented, many production systems don’t always include antibiotics in all nursery diets, particularly during the latter stages. The perceived cost of the antibiotics may be a concern, but the primary reason for limiting antibiotic use in nursery diets is often to provide a period to administer oral vaccines.

We recently collaborated on two trials to help determine the production and economic impact of removing antibiotics from different nursery diets and the economic return achieved with various commonly used feed-grade antibiotics. In both cases, the pigs evaluated had a history of enteric and respiratory challenges involving a variety of organisms, including Pasteurella multocida. The pigs were from a positive porcine respiratory and reproductive syndrome sow herd but a stable pig flow.

Measurements included evaluations at days 0, 10, 21 and 42; pen weight; feed disappearance; and feed cost. An important metric also considered was margin over feed cost. This was calculated as pounds of gain multiplied by the value of the gain, minus feed cost per pig.

Evaluating the Economics

In the first trial, we compared the commonly used active ingredients tiamulin, chlortetracycline, carbadox and oxytetracycline against a control group. A total of 1,008 pigs (beginning at 11.9 pounds and 19 days of age) were studied in a 42-day experiment to determine the antibiotic regimen’s influence on growth performance and economic return.

The feeding regimens proceeded as follows: From day 0 to day 10, pigs received diets containing either no antibiotic or tiamulin at 35 grams per ton and chlortetracycline at 400 grams per ton. From day 10 to day 21, diets contained either no medication, tiamulin/chlortetracycline, carbadox at 25 grams per ton and oxytetracycline at 400 grams per ton, or carbadox at 50 grams per ton. From day 21 to day 42, diets contained either no medication or tiamulin/chlortetracycline.

In a follow-up study, we evaluated the return on investment from tiamulin and chlortetracycline, tilmicosin, carbadox and oxytetracycline. We again studied 1,008 weanling pigs (beginning at 12 pounds and 19 days of age) in a 42-day experiment with a control group.

The feeding regimens involved: From day 0 to day 11 and from day 11 to day 21, pigs were fed diets containing either no antibiotic; a combination of tiamulin at 35 grams per ton and chlortetracycline at 400 grams per ton; or tilmicosin at 363 grams per ton from day 0 to day 11, and 181 grams per ton from day 11 to day 21. From day 21 to day 42, pigs previously fed tiamulin/chlortetracycline or tilmicosin were fed diets containing either no medication, tiamulin/chlortetracycline, or a combination of carbadox at 25 grams per ton and oxytetracycline at 400 grams per ton. (See sidebar at left for results.)

The Take-home Message

Including antibiotics in all phases of the nursery diet — including the latter stages — improves pig-growth performance through an increase in feed intake, which boosts daily gain. Eliminating the medication-free window — and shifting vaccine-administration timing — can result in heavier pigs and improved feed efficiency.

Understanding the differences between antibiotic regimens and choosing the right one for your operation also can improve the return on investment from your herd-health program.


Trial 1 Results

The following results are significant, unless otherwise stated. Comparisons are against controls.

Day 0 to day 10:

  • Tiamulin and chlortetracycline improved average daily gain, feed conversion and  margin over feed cost (P < 0.01).
  • Margin over feed cost increased to 22 cents and 62 cents per pig when antibiotics were added to the diet and gain was valued at 50 cents per pound and $1 per pound (P < 0.003 and 0.002, respectively).

Day 10 to day 21:

  • All antibiotics improved average daily gain, average daily feed intake, feed conversion and margin over feed cost (P < 0.01).
  • Tiamulin and chlortetracycline showed average daily gain tending higher than carbadox and oxytetracycline (P < 0.09), and average daily gain, feed conversion and margin over feed cost tending to be improved compared with carbadox at 50 grams per ton (P < 0.07).
  • Margin over feed cost increased to 49 cents and $1.29 per pig when antibiotics were added and gain was valued at 50 cents per pound and $1 per pound (P < 0.0001 and 0.0001, respectively).

Day 21 to day 42:

  • Tiamulin and chlortetracycline improved average daily gain, average daily feed intake and feed conversion (P < 0.05).
  • Tiamulin and chlortetracycline improved margin over feed cost when gain was valued at $1 per pound (P < 0.01).
  • Margin over feed cost increased to 26 cents and $1.32 per pig when tiamulin and chlortetracycline were added; gain was valued at 50 cents per pound and $1 per pound (P < 0.16 and 0.01, respectively).

These results demonstrate that adding antibiotics to the nursery diet improved pig performance and economical return in this commercial farm.


Trial 2 Results

The following results are significant, unless otherwise stated. Comparisons are against controls.

Day 0 to day 21

  • Both tiamulin/chlortetracycline and tilmicosin improved average daily gain, average daily feed intake and margin over feed costs (P < 0.01).
  • Tiamulin/chlortetracycline tended to improve feed conversion compared to tilmicosin (P < 0.09).
  • Tiamulin/chlortetracycline lowered feed cost (P < 0.01) and improved margin over feed cost to 66 cents and $1.05 per pig when gain was valued at 50 cents per pound and $1 per pound compared to tilmicosin (P < 0.01 and 0.013, respectively).

Day 21 to day 42

  • Tiamulin/chlortetracycline and carbadox/oxytetracycline increased average daily gain, average daily feed intake and margin over feed cost (P < 0.05).

For the overall trial, adding antibiotics to the diet during any phase improved average daily gain, average daily feed intake and margin over feed cost. These results confirm the findings of our initial study that adding antibiotics to the nursery diet improved pig performance and economic return in this commercial farm.