Alternatives to antibiotic growth promoters (AGPs) can maintain broiler performance. But replacing antibiotics is not a simple matter of like-for-like replacements, according to Doug Korver, PhD, professor of poultry nutrition at the University of Alberta.
Regulating inflammation caused by pathogens in broilers’ environments is metabolically expensive, Korver said, and the success of AGPs is rooted in the fact that they control that inflammation and allow for greater production efficiency. He pointed to international studies suggesting that removing these products is likely to result in increased feed-conversion ratio and production costs.
However, he noted, major surveys have found that approximately a third of global poultry production is totally antibiotic free, and roughly a quarter is 50% to 99% antibiotic free. There is a big market for alternatives, and the options are many: pro- and prebiotics, synbiotics, organic acids, fatty acids, oligosaccharides, essential oils, enzymes, yeast cell walls and bacteriophages.
Testing combinations
All the alternatives differ in their modes of action, he noted, and the challenge is to find combinations with synergistic effects.
“Antibiotics work well against a lot of different challenges. The alternatives tend to be much more specific than that,” he told an audience as part of Canadian Poultry’s 2025 Broiler School webinar series.
“Talking to producers who have gone antibiotic-free, and from my own research experience, it’s clear there is not a single antibiotic replacement that is as effective as antibiotics. You can’t just take out antibiotics, put in one antibiotic-alternative product and have the same level of protection.”
A large-scale study in Ecuador by Korver’s team followed over 2 million birds from placement to processing on three different treatments:
- Treatment 1: Basal diet with an AGP
- Treatment 2: AGP replaced with a probiotic, enzymes and an increased phytase dose
- Treatment 3: Removal of some of the alternatives to reduce costs
The researchers observed no significant difference in bird performance between the three treatments, both in terms of 44-day bodyweights and maintaining the European Production Efficiency Factor, which accounts for feed conversion, daily gain and mortality.
“The take-home message is that it is possible to raise broilers efficiently without the use of AGPs, and it will require multiple overlapping and complementary alternative strategies,” Korver explained.
Study design is crucial
Such research can demonstrate the effectiveness of antibiotic-alternative strategies under commercial conditions. However, Korver was critical of the design of some studies that claim the efficacy of alternative products, based on simply comparing an antibiotic and an alternative in sterile experimental facilities and seeing no performance difference.
“That is a very problematic way of approaching the question, because what happens if there was no antibiotic and the birds grew just as well? It would tell you that there was no challenge — there was nothing for the antibiotic or the antibiotic alternative to do. So, you really can’t confidently say that the product was an effective anti-microbial replacement,” he said.
“What you want to see in experiments is some sort of demonstration that there’s a loss in performance when no antibiotics and no alternatives are provided, so there’s actually a challenge there that needs to be dealt with.”
Starting with biggest problems
Ultimately, AGP replacements are “not going to cure bad management,” he stressed, and each package of antibiotic alternatives needs to be tailored to what’s going on in the field.
“One of the challenges we face as an industry is that different environments can have different microbial challenges, whether that’s comparing barn to barn, farm to farm or region to region. It really is a matter of being strategic about how you approach going antibiotic-free,” he said.
“Start with the biggest problem, the first challenge you need to dial in. Then, if you feel that [the product] gives you some protection against your biggest problem, look at what other products you can try to deal with the lower-impact challenges. It takes time, good records and a strategic approach to figure out what combination works well.”
