Antimicrobial growth promoters (AGPs) are the target of those who argue that using antibiotics in animal feed at low levels for long periods of time is improper and dangerous to human health.

Those critics suggest that such use promotes antimicrobial resistance in food-borne pathogens, which could be detrimental for humans who could contract a food-borne illness resistant to normal treatments.

The European Union has banned the use of most AGPs based on a classic application of the “precautionary principle” which essentially says: “if there is any risk, do not use the product.”

AGPs have been used for about 50 years. Even though antimicrobial resistance has increased across the board, when groups of truly independent, unbiased scientists looked at the issue, they have concluded that the risk to humans from AGPs is of no consequence. Some have even suggested that human health may actually be at higher risk without them.

If there was a risk to human health, the Food and Drug Administration (FDA) would never approve these products. Having said that, some people still suggest taking a serious look at our use of AGPs, not because of human health, but because of economics.

Research Assessment

Recent research from Kansas State University called into question the cost:benefit ratio of using AGPs in modern, three-site, high-health herds. The researcher in this case has called on producers to assess the need for AGPs in their own unique situation. In addition to total disease load on a farm, there are other factors that may come into play when deciding to use AGPs. Pig flow issues such as multiple sites and all-in, all-out have an impact on overall performance, and these issues should also be considered in the decision to use AGPs.

Other factors may include genetics, stocking density, vaccination protocols, facility design, season, the number of sources contributing to a group and the quality and density of feed.

Besides safety, the FDA has always required companies to prove AGPs are efficacious to meet product claims.

Hundreds of published reports have shown, that in the vast majority of trials, these products have proved beneficial. Those results are what most producers base their decisions on today.

On-Farm Trial

If you consider running an on-farm trial to determine the benefits of AGPs in your system, you must do it right to get information that is useful in the decision-making process. There is a University of Nebraska publication called “Conducting Pig Feed Trials on the Farm” available online at:

Since AGPs claim to make relatively small improvements in feed efficiency and average daily gain, any trial must include many replications to determine any statistically significant differences. This publication outlines details of conducting the on-farm trial correctly and helps avoid some of the common pitfalls of on-farm feed trials. If you are not dedicated to doing it right, don't waste your time!

Case Study

On a recent farm visit, a client wanted to know what more he could do to cut costs during this down cycle of hog prices. Everything was potentially on the chopping block, including any of the AGPs that were being fed through the nursery and grower phases.

First, we considered the disease profile of the farm and what benefits we assumed were gained by the AGPs. Since the nursery phase has shown more disease problems, and current science has shown the largest benefit from AGPs is in this phase of production, we decided to continue using them in the nursery.

We followed the same process for the finishing phase, weighing the importance of throughput, stocking density and which diseases would be controlled or influenced by the AGPs.

The next step in the decision process is to calculate the cost of the growing and finishing rations and estimate the cost of adding the AGPs to these rations. Finally, using estimates of improvement in performance to average daily gain and feed efficiency, we can calculate the expected cost:benefit ratio.

Return on Investment

In this case, we calculated a return of over 50% on the investment made in AGPs. As the price of grain and soybean meal rises, making feed more expensive, the cost:benefit ratio improves.

Although AGPs require an additional cash outlay, the price of hogs does not affect the return that is generated on each dollar invested in the AGPs.

Our next step is to set up an on-farm trial to gather the actual data and set of circumstances for this particular farm. Until then, we decided to retain the competitive advantage that AGPs provide for this hog operation.