Antibiotic feed/food supplementation

Many domesticated animals show increased growth and improved feed efficiency when given low doses of antibiotics.  In fact, this is by far the biggest use of antibiotics.  Mostly you hear about this in the context of worries about how this may select for resistant bacteria (which may well be true), but one interesting question is why it even works – and what other applications this technique might have.

It strikes me that it might be useful in food emergencies – famines and so forth.  The dosage is low (200 g per ton) and can increase feed efficiency over 10% in some cases.  Assuming that antibiotic supplementation works in humans (which is likely, considering that it works in a wide spectrum of domestic animals), you might be able to save 5 or 10% more people with a given food supply. Now if we ever bothered to learn exactly how this works, we might be able to find an equivalent approach that didn’t use antibiotics, some other way of knocking out certain pathogens (phage therapy?) or altering the gut flora.

This entry was posted in Uncategorized and tagged . Bookmark the permalink.

38 Responses to Antibiotic feed/food supplementation

  1. JayMan says:

    Well, there is the idea that something with gut flora is behind the rise in obesity. Misdreavus had something to say on that. Perhaps a certain antibiotic is involved?

  2. A Chicken says:

    Farm animals live in very dense conditions with very poor sanitation. For chickens they grow up in a massive cake of excrement with may a square foot of space per bird.

    Under those conditions I’d think the effects of antibiotics would be amplified relative to what you would see in humans. Do you get the same growth boosts even for animals raised in better conditions?

    Also, wouldn’t this effect have shown up in studies of low-dose antibiotics?

    • A Chicken says:

      Human studies of sustained antibiotics administration, that is.

    • gcochran9 says:

      Farmers use nonabsorbable antibiotics: they are thought to work by changing the gut flora. As far as I know this has never been tested on humans, but it works on a wide variety of farm animals.

      The thing to do is test it, not blurt forth uninformed reasons why it couldn’t possibly work.

    • Priceequation says:

      According to a class I took with Harpending, there are actually human studies, and it works. If I remember correctly, giving poor kids low-doses of antibiotics brings their body weight up: from below-average to average. And that’s without adding any food or anything else. Just giving away free antibiotics.

      • Priceequation says:

        There were also a series of Russian studies where convicts were given free antibiotics mixed in with crappy fermented yoghurt. I forget if that benefitted them or not to ingest the stuff.

      • Priceequation says:

        Although I think they were fairly small sample sizes. Nowadays it would be against “ethics” to give away free meds to kids. Total shame.

  3. Henk says:

    Possibly part of a starvation adaption, so your first experiment is if this still works when underfeeding the animals. That’s where I’d place my bets.

  4. dearieme says:

    Heart attack rates increased sharply from the 20s to the 60s, and then declined sharply. Apparently neither the rise and fall of smoking, nor changed diets, can explain it. I wonder whether the cause of the rise was bacterial, and the decline is a result of all that “over prescribing” of antibiotics that is complained about. Maybe there was a bit of help from antibiotics in meat, too?

    • mysterian says:

      See Review and Hypothesis:
      Vulnerable Plaque Formation from Obstruction of Vasa Vasorum by Homocysteinylated and Oxidized Lipoprotein Aggregates Complexed with Microbial Remnants and LDL Autoantibodies (online at

      • dearieme says:

        Thank you for that. I particularly noticed “An apparent contradiction to our interpretation is that prevention of cardiovascular disease by antibiotics has been largely unsuccessful. However, in these trials patients have usually received a single antibiotic … and the trials have been of relatively short duration.”

        So my conjecture that an (accidental) cocktail of antibiotics, accumulated over a large chunk of a lifetime, may have proved effective is not necessarily cock-eyed.

  5. IC says:

    “knocking out certain pathogens (phage therapy?) or altering the gut flora”
    It has been mystery to me that how antibiotics achieve those food effect. This sounds very plausible explanation. Or bacteria simply consume a lot of energy from feeds without antibiotics.

    Low dose of antibiotics can cause bacteriostatic effect (some antibiotics only wiht bacteriostatic effect). Reduced metabolism of bacteria can have direct result of low energy consumption (or low consumption of feed nutriention).

    • IC says:

      This might also explain fattening effect of American diet (or food). In China, food produced by traditional farming is not only tasting better also less fattening which might be result of less contamination with antibiotics.

      If Germs in your guts are less active, extra energy will be picked up by your body.

      • dearieme says:

        “In China, food produced by traditional farming is not only tasting better …”: maybe, but several Chinese acquaintances of my wife have remarked on how much better pork is here (UK) than in China.

        • Difference Maker says:

          Interesting. There were different domestication events

        • IC says:

          “several Chinese acquaintances of my wife ”

          Quite of indirect connection here. lol.

          As a Han Chinese person, I grew up in Chinese countryside. The pork from Chinese farmer home raised pigs is unbeatable in flavor in my taste. Nowaday, the pigs from specialized pig farm for commercial production are no difference from American pig farm in term of pig breed and technique and feed. But some farmers still raise pigs in their home yard. Only those free roaming home raised pigs taste better.

          In USA, I often go on hog hunt in the woods. Those hybrid wild hog between domestic and wild boar have the best flavor. Pure wild boar actually taste too strong, almost stink.

  6. The most obvious mechanism to test here is if just knocking out some of the gut bacteria is resulting in more of the food calories going to the animal rather than the gut bacteria. (Second would be testing if knocking out specific gut bacteria has that effect.) Seems like some kind of occasional purgative/laxative could have a similar effect on physical levels of gut bacteria, without using antibiotics?

  7. That is very interesting. I had no idea that such a low dose of antibiotics in animal feed creates such a difference in efficient food consumption by our tasty friends.

    This area definitely deserves more research. I for one would shell out big bucks if someone could tell me how I could consume food less efficiently without the nasty side effects of hunger, or eating how I damn well please. Give me a pill that puts more bugs in my gut without nasty side effects that makes food consumption 10% less efficient and I would wash it down with a cheese burger multiple beers.

  8. jjameselliott says:

    There’s also a benefit obtainable by boosting certain types of gut flora, i.e. probiotics

  9. DK says:

    With age, I noticed that various small wounds started to take considerably longer to fully heal. Then I discovered a cure: no matter how tiny a cut or an abrasion, always put a large wad of triple antibiotic ointment (bacitracin, neomycin, polymyxin B), then cover with bandage. The difference it makes is amazing!

    I suppose it is possible that it is due to the fact that Vaseline-based cream does not allow oxygen access to the surface of the wound, but I think more likely is that even a small drop in immune status can make a difference. And that the main thing that prevents wound healing are the little harmless bugs on the skin.

    Could be that there are a lot of bugs with similarly small effects in many places of the body. Our insides are supposed to be sterile but in reality they rarely are.

    • Sean Fielding says:

      The surface of our gut is no more part of our true inside than is the surface our skin. The urinary and reproductive tracts represent zones with fairly abrupt transitions between true inside and true outside that, especially in women, can be imperfect barriers. The respiratory tract, a more gradual transition. Everywhere else inside should be sterile almost all the time in a healthy person, no?

    • athEIst says:

      I also noticed with age bacitracin, neomycin, polymyxin B help in wound-healing but hydrocortisone is so much faster

  10. Nobody Important says:


    Greg, would you mind commenting on this study?

    The Evolutionary Dominance of Ethnocentric Cooperation

  11. We can cultivate gut bacteria and transfer them between humans

  12. JP Straley says:

    Ha ha ha. Feed them arsenic! Eh? Well, the poultry industry has fed broilers low doses of organometallic As for years and years. Recently EPA said Boogey on Yer! and shut it down, but there’s no doubt that it slightly increases food utilization in the gut. Why? Prolly ’cause the lining cells shed and new ones come on duty a bit faster. New = better.

  13. Veracitor says:

    Perhaps some past human populations already used antibiotics to improve food utilization or general health. There is evidence for ancient Nubian peoples fermenting and consuming tetracycline-like antibiotics:

Leave a Reply

Fill in your details below or click an icon to log in: Logo

You are commenting using your account. Log Out /  Change )

Google photo

You are commenting using your Google account. Log Out /  Change )

Twitter picture

You are commenting using your Twitter account. Log Out /  Change )

Facebook photo

You are commenting using your Facebook account. Log Out /  Change )

Connecting to %s