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This post was written as a research project investigating whether it would be net positive for animals to pursue an intervention looking to reduce or eliminate antibiotic use in farmed animals. 

Many thanks to Vicky Cox, Cecilia Tilli, Phil Brooke, and Cóilín Nunan for their help and contributions. 

Antibiotic resistance in farmed animals

Executive summary

Reducing antibiotic use in farms is very likely to be net positive for humans. However, it is not clear whether it would be net positive for animals. If farmers stop using antibiotics, animals might suffer from more disease and worse welfare. This effect might be mitigated by the fact that (i) farmers can replace antibiotics with substitutes such as probiotics, prebiotics, and essential oils, which also prevent disease, and (ii) farmers might be motivated to make adaptations to farming practices which prevent disease and also benefit animal welfare, such as lowering stocking density, reducing stress, and monitoring disease more closely. It is not obvious how likely it is that farmers will take these disease-mitigating measures, but since high disease rates increase mortality, decrease carcass profitability, and could cause reputational damage, it is plausible that they will be motivated to do so. Alternatively, animal advocates could take the 'holistic strategy' of promoting welfare measures which also tend to cause reduced antibiotic use. Tentatively, I take the view that eliminating antibiotic use on a farm would not lead to worse lives for those animals.

Eliminating antibiotics might also be expensive for producers, and because of this, it could increase the price of animal products in the short term, which would be good for animals. The literature weakly supports the view that meat prices will increase following an antibiotic ban. However, there is also some support for the view that price will increase differentially for smaller and larger animals, which lands us with the small animal replacement problem. This problem could be avoided by the approach taken to the intervention, e.g. a corporate campaign targeting only small animals.

1. The problem

Antibiotics are used on farmed animals. They are used to treat disease (therapeutic use), to prevent disease (subtherapeutic or prophylactic use), and to promote animal growth (growth promotion use). In the US 70% of antibiotics (by weight) are used on non-humans, and figures are similar globally. Antibiotic use selects for bacteria which are resistant to that antibiotic, and therefore promotes the development and proliferation of antibiotic resistant bacteria. This leads to the spread of antibiotic resistant disease, which may be hard to treat.

It should be noted that antibiotic use by weight does not indicate that 70% of antibiotic resistant disease is due to antibiotic use on farms; resistant bacteria must transfer from farmed animals to humans, and it is currently very unclear how efficiently this transfer can occur. But it is at least evident that some proportion of antibiotic resistant disease is caused this way.

The most apocalyptic predictions suggest that antibiotic misuse means that humans will return to pre-antibiotic levels of mortality and morbidity. So we might expect that reducing antibiotic use in farming could have a large impact on public health.

2. Potential models for a solution

1. We could pursue a ban on antibiotic use on farmed animals:

  • (i) total ban (incl. therapeutic use)
  • (ii) ban on subtherapeutic use
  • (iii) ban on growth promotion use
  • NB. (ii) and (iii) are already in force in some countries e.g. EU and UK, but no country has a total ban.
  • (iv) different levels of ban for antibiotics of different levels of importance for human medicine (e.g. total ban for Highest Priority Critically Important Antimicrobials, subtherapeutic ban for others, etc.)

2. We could pursue tax incentives for eliminating antibiotic use.

3. We could operate a corporate campaign demanding that companies eliminate antibiotics in their supply chain.

4. We could work with farmers to help them eliminate antibiotics on their farms.

5. We could promote animal welfare measures which tend to make farmers reduce antibiotic use (e.g. Dutch slower-growing chickens and delayed piglet weaning). 

6. We could pursue model 5 alongside some combination of 1-4 (the 'holistic strategy'; see section 4).

I’m not sure which of these is the most promising. I am fairly confident that a total ban would be net negative for animals because it would mean that some diagnosed diseases might have to go untreated. This view was supported by Phil Brooke of Compassion in World Farming. A corporate campaign can target one particular industry, which might have advantages if we consider the small animal replacement problem (see section 8).

3. Effect on animal welfare

Having fewer antibiotic resistant diseases benefits humans, but we can also expect it to benefit animals. Diseases animals get can be antibiotic resistant too. Cóilín Nunan of the Alliance to Save Our Antibiotics gives an example: 'On some intensive pig farms strains of a disease called swine dysentery have emerged which are resistant to all available antibiotics and are therefore untreatable. As a result all the pigs on the farm have had to be culled.'

A potential concern, however, is that because antibiotics are used to prevent and treat disease, reducing or eliminating antibiotic use would lead to animals having worse lives overall, because they would suffer from more disease. If this is the case, reducing antibiotic use should not be recommended as an intervention to help animals, because it would be net negative for animals.

However, it might not be the case that there is an overall decrease in animal welfare following reduced antibiotic use. There are still incentives for farmers to prevent disease by means other than antibiotics. Here are three reasons why farmers can’t let disease totally run rampant without mitigating it at all:

1) lowered profits due to mortality and carcass contamination from disease

2) animal welfare laws and/or animal welfare certifications

3) public health concerns and reputation damage from e.g. Salmonella, E. coli

I’m not sure how strong these incentives would be; according to Phil Brooke, 1 is the key incentive. 2 and 3 seem less strong, and depend on the country we are talking about. It may be the case that these incentives force farmers to do something to mitigate disease. Whether we think this is likely will greatly affect whether this intervention is net positive for animals.

There are two broad categories of things farmers might do to mitigate disease:

  1. Welfare adaptations: Farmers could take steps that overall improve animal welfare. This is because a lot of things which happen to align with animal welfare goals also decrease the incidence and spread of disease; for example, reducing stress, decreasing stocking density, and improving hygiene. So these animals’ lives would be better overall.
  2. Antibiotic substitutes: Farmers might use different methods to treat and prevent disease instead of antibiotics, which might be just as effective. So we would see no increase in incidence of disease, making these animals’ lives neither better nor worse overall.

4. Welfare adaptations

Compassion in World Farming (CIWF) has a guide on how farmers can adopt an ‘Antibiotic Stewardship Programme’ to reduce or eliminate antibiotic use. They list welfare adaptations farmers can make to reduce disease incidence following elimination of antibiotic use:

  • Lowering stocking density
  • Using more robust breeds (e.g. slower growing broiler breeds)
  • Good environment
  • Disease surveillance
  • Good diet
  • Hygiene
  • Biosecurity
  • Well-managed regrouping & mixing
  • Good breeding
  • Decreasing stress
  • Avoiding routine mutilations (castration, tail docking, tooth clipping)
  • Avoiding social isolation (e.g. dairy calves, sow stalls)
  • Greater space allowance
  • Outdoor access (esp. pasture-raising)

These types of change seem robustly good for animal welfare (indeed some are the same changes animal advocates campaign for!), and, although a detailed investigation into whether they prevent disease was not conducted, it appears to be consensus that either these adaptations would be as effective as antibiotics at preventing disease or the welfare gain from these adaptations would outweigh the modest increase in disease we might see.

It seems convenient that the effects of preventing disease and increasing welfare align in this way. It’s possible that there are some ways of mitigating disease spread which are worse for animal welfare; two examples are (i) vaccinations in fish - they prevent disease, but seem very stressful, and (ii) it is speculatively possible that larger farms have better biosecurity, so elimination of antibiotics might lead to integration of smaller farms. I did not however find any evidence of measures like this being taken, nor have reason to suppose they outweigh welfare-positive adaptations.

The most important consideration for welfare adaptations is whether farmers would be motivated to adopt them, without advocates specifically campaigning for them to do so (i.e. models 1-4 in section 1). I remain very uncertain on this issue, but tentatively think it is likely that profit incentives might make farmers make some adaptations. This is probably much more true in larger animals, in whom disease and mortality is more costly, since the market price per animal is higher. See also below (section 6) on limited evidence of welfare reforms following antibiotic elimination in industry.

If we think it is probable that farmers will not adopt welfare adaptations without pressure, then models 5 and 6 look more promising, as they are targeted specifically at securing welfare reforms. Phil Brook and Cóilín Nunan were both of the opinion that model 6, the 'holistic strategy', was the best option, stating that we must pursue bans on subtherapeutic and growth promoting use as well as advocating for welfare reforms. 

Intuitively, my view is that pursuing a single strategy directed explicitly at reducing antibiotic use would be more cost-effective on the margin, but I did not attempt to substantiate this as part of this project. I would be very interested in a more thorough look at this question. 

5. Antibiotic substitutes

Substitutes are relatively new and as such there are some open questions about the mechanism by which they prevent disease and their efficacy. See this piece for a more detailed look at antibiotic substitutes in extant literature.

Probiotics - available commercially & the most popular alternative currently used in industry.

  • Work via ‘competitive exclusion’. Application is painless - applied via spray or drinking water
  • CE preparations have been used in Finland since 1976 - now in ~90% of birds in Finland.

Prebiotics - increase gut health by stimulating harmless bacteria

Essential Oils - seem to combat Salmonella, and have antimicrobial properties in vitro.

Efficacy of these alternatives

  • ‘Some of the replacement products such as organic acids, essential oils, herbs, probiotics, and prebiotics have been found to be variably effective to control these pathogens, but none of these alternatives has been proven as efficient as [antibiotics] in maintaining high production yields and controlling necrotic enteritis.’ (source)
  • ‘To date, there are no reports on the effect of a combination of these products on economic and health conditions in commercial field trials’ (ibid.)

6. Current industry practices

This section is focused on chicken production in the US, because there is more evidence available in this area. A number of prominent chicken producers sell their meat with the label ‘No Antibiotics Ever’, and charge extra for this than ‘conventional’ equivalents. I looked for evidence that producers (i) were using antibiotic substitutes, (ii) had seen a change in incidence or severity of disease, and (iii) had made welfare adaptations.

(i) Perdue - eliminated subtherapeutic antibiotic use as of Oct 2016

Substitutes: Uses an undisclosed probiotic and oregano [essential oil?] (source)

Adaptations: Reduces stress by turning lights off for 4hrs per night (ibid.)

In 2018-2020, ‘Perdue Farms achieved a Tier 2 ranking from the Business Benchmark on Farm Animal Welfare (BBFAW) for the company’s animal welfare protocols.’

  • The methodology report of BBFAW suggests that it is a genuine measure of animal welfare, and it’s promising evidence because it’s independent of Perdue. BBFAW does not mention disease incidence as a criterion for assessment, so Perdue’s BBFAW ranking gives us some evidence that eliminating antibiotics has not changed their chickens’ welfare, but no clear evidence on disease.

Perdue’s 2019 animal care report is (obviously) very positive about what they’ve achieved and how good their chickens’ welfare is, etc.

  • Gives nothing specific on disease incidence, but ‘Improved bird health leading to a drier environment’ is noted as a contributing factor in decreasing the instance of foot pad dermatitis in their chickens. Speculatively, this could be because incidence of enteritis has been reduced (since enteritis makes litter wet).

(ii) Tyson - eliminated all antibiotic use from 2018

Substitutes: probiotics and essential oils (thyme, oregano, yucca, and peppers)

Adaptations: ‘We've redesigned our chicken's housing to give them plenty of room to roam.’ (source - Tyson’s website) ‘Through sanitation and better rearing practises, we can keep our birds healthy without antibiotics’ (source - a Tyson PR video)

However, we probably shouldn’t take this very seriously, as it’s PR from Tyson itself.

This page suggests a year-on-year improvement in animal welfare, including Acceptable Paw Scores of 78.0% in 2018, and 81.0% in 2019. Lower incidence of FPD could, as above, be used as an indicator that enteritis has also decreased.

However, this article notes that Tyson has a history of lying about antibiotic use on its farms.

(iii) Pilgrim’s Pride - working to reduce antibiotic use (unclear date/progress)

‘As part of our long-standing commitment to safeguard the welfare of our chickens, we treat all sick animals with antibiotics, if necessary, and then remove them from our antibiotic-free/NAE and organic programs. We will never allow a sick animal to suffer.’

  • This is couched in PR language, but does at least suggest that antibiotic-free commitments do not incentivise producers to allow disease to run rampant.

7. Effect on price of animal products

Quite separately to the other considerations, reducing antibiotic use could end up being good for animals if it increased the price of animal products (and thus decreased demand, leading to fewer animals raised and killed for food). It is somewhat unclear whether this would happen, but I am overall quite confident that we would see at least a short term increase in price of meat following an antibiotic ban. The following is a non-exhaustive review of the literature on this topic.

The Use of Drugs in Food Animals: Benefits and Risks. National Research Council (1999)Moderately towards price increase (++)‘the average annual per capita cost to consumers of a ban on subtherapeutic drug use is $4.84 to $9.72.’
Growth Promoting Antibiotics in Food Animal Production: An Economic AnalysisWeakly towards price decrease (-)Based solely on data from Perdue; seems of limited cross-applicability.
A randomized controlled trial to evaluate performance of pigs raised in antibiotic-free or conventional production systems following challenge with porcine reproductive and respiratory syndrome virusWeakly towards price increase (+)net revenue per pig was $105.43, $98.79, and $33.81 for two conventional groups and antibiotic free respectively.
Experiences with drug-free broiler production (Smith 2011)Weakly towards price increase (+)I don’t put much weight on this study - some uncited opinion/predictions
Impact of a drug-free program on broiler chicken growth performances, gut health, Clostridium perfringens and Campylobacter jejuni occurrences at the farm levelModerately towards price increase (++)‘The drug-free program was associated with a significant increase in feed conversion ratio and a decrease in mean live weight at slaughter and in daily weight gain.’ - They did not estimate the cost of this, but this would cost money.
The effect of discontinuing the use of antimicrobial growth promoters on the productivity in the Danish broiler productionWeakly towards price increase (+)‘the feed-conversion ratio increased marginally 0.016 kg/kg’ - So evidence for mildly increased cost.
The Effect of Withdrawing Growth Promoting Antibiotics from Broiler Chickens: A Long-Term Commercial Industry StudyWeakly towards price increase (+)‘average increase in feed conversion ratio of 0.016 on DMV and 0.0.012 in NC.’
Economic Impacts of Banning Subtherapeutic Use of Antibiotics in Swine Production (Brorsen et al. 2002)Weakly towards price increase (+)‘A ban on the use of antimicrobial agents as growth promotants for swine would be costly, totaling $242.5 million annually, with swine producers bearing $153.5 million of the cost in the short run.’
Economic Effects Of A Ban Against Antimicrobial Drugs Used In U.S. Beef ProductionVery uncertain - introduces countervailing considerations‘Results indicate that regulating [antibiotics] in livestock production would increase per-unit costs of producers previously using drugs and reduce beef supplies in the short run, reducing consumer surplus. Producers not previously using drugs would benefit from short-run price increases.’
How Factory Farms Play Chicken With Antibiotics – Mother JonesVery uncertain - not a study, and not sure if paid promotion‘Perdue spends an extra $3 to $4 for every $1 it saves in antibiotics reduction—but recoups those costs by charging shoppers a premium for that meat.’

It’s also possible that eliminating antibiotics could actually net increase demand for meat if consumers think that antibiotic-free meat is better/healthier/more natural.

  • Three studies mention the possibility of increased demand; one thinks increased demand would more than compensate for the costs of increased production following a ban, another estimates that it would exactly offset the increased cost, and a third thinks we should assume no increase in demand. It’s therefore unclear what to conclude on this issue.

8. Price and the small animal replacement problem

If replacing antibiotics raises the price of meat, there is a further question whether the price of different meats rise differentially, and if so, whether the cost of small animals like chicken or fish might rise less than the cost of larger animals like cows. If that were to happen, we would run into the small animal replacement problem (SARP).

There is only one study which estimates the relative price change for different meat industries following an antibiotic ban, which does indeed suggest that chicken would increase in price less than beef and pork. This piece suggests that the reason for this is chickens’ shorter life cycles, so changes are more easily tested and adapted to.

If that’s right, then we should be less confident that a ban across industries would be net positive for animals, but we could nevertheless sidestep SARP by pursuing a corporate campaign targeting chickens only. This might make sense, given that this is the industry which has seen the most success eliminating antibiotics so far, and consumer demand appears to be there, given the commercial success of ‘No Antibiotics Ever’ labels.

One weakness of this approach is that I am not sure whether we could ask for a commitment to no subtherapeutic antibiotic use - would this be easily communicable, would it incite consumer pressure, and would it be an appropriate virtue signal for the corporation? Perdue and Tyson’s ‘No Antibiotics Ever’ label is much more categorical and obvious than ‘no subtherapeutic/prophylactic antibiotics used’ and looks better on a label or a menu. This might be able to be mitigated by the right framing of the campaign - e.g. ‘Responsible antibiotic use’ or ‘Antibiotic Stewardship’ (this latter is used by CIWF).


I tentatively support the view that an intervention using at least one of the strategies I have outlined would be net positive for animals, and that animal advocates should be optimistic about pursuing an intervention in this area.

My opinion would be changed if I found:

  • Evidence that farmers do not make welfare adaptations following elimination of antibiotic use
  • Stronger evidence that antibiotic substitutes such as prebiotics, probiotics, and essential oils are less effective than antibiotics at preventing disease
  • Evidence that eliminating antibiotics lowers the price of meat
  • Stronger evidence that eliminating antibiotics raises demand for meat
  • Reasons to think that a corporate campaign in this area would not be viable
Sorted by Click to highlight new comments since: Today at 12:58 AM

This reminds me of a speech given by the head of Sanderson Farms a few years ago, during an industry-wide conversation about the merits of antibiotic-free farming. It stood out for me because it is rare for CEOs to take a public stance against a popular cause in this way.

Much has been written and discussed in recent weeks regarding the production and use of antibiotic-free chicken. In response to the announcement by several large users of chicken that they will move to antibiotic-free chicken over time, several processors in our industry have responded that they, too, will move to the production of antibiotic-free products.
After very deliberate, careful. And measured consideration of this issue, we informed our customers last week that we will continue our responsible use of antibiotics when prescribed by our veterinarians. This decision is based on animal welfare, environmental considerations. And food safety. First, we believe we have a moral obligation to care for the animals under our stewardship. Just as our vets do not compromise there oath to relieve the suffering of animals, our obligation to care for the animals under our care is not subject to compromise.
It is instructive to us that this discussion has revolved primarily around chickens. And no one, to our knowledge, has suggested that other species be denied care and medicine. It seems to us that if an animal is sick and its suffering would be relieved from the use of FDA-approved antibiotics, it does not matter if it is a chicken, cow, hog, or household pet. That animal should be treated.
We also have a commitment to environmental stewardship. Sick chickens do not perform well. When a chicken gets sick, it takes longer to reach market weight. It takes more feed to produce a pound of meat and it just performs poorly. Because its performance decreases, it takes more water, more feed, electricity, natural gas. And other resources to raise the bird. More feed means more acres, more water. And more fertilizer to grow grain. Given the number of animals on the ground in the United States for food production, even small changes in the performance of those animals could have a significant negative environmental impact. Simply stated, neglecting the health of our chickens is inconsistent with our environmental sustainability goals and our commitment to the judicious use of water and other natural resources.
Finally, healthy chickens are safe chickens. In our judgment and based on the experience in Europe, unhealthy chickens are more likely to carry higher loads of Salmonella, Campylobacter and E. coli. Our Company and our industry have made great strides in recent years to reduce these bacteria. And that work is in jeopardy if we neglect bird health.
Like everyone else, we understand the anxiety created by fear of antibiotic resistance caused by the misuse and overuse of antibiotics. We also are aware that there has been no credible scientific evidence that supports the notion that antibiotic resistance in humans is made more likely because of the use of antibiotics in chickens. Indeed, because of withdrawal periods mandated by the FDA, there are no antibiotic residues in chicken meat marketed in the United States. And in that sense, all chicken is antibiotic-free.
We will continue to work with our pharmaceutical suppliers to find alternatives to antibiotics important in human health. And we are committed to using alternatives when they become available. But until such alternatives are developed, we will treat the animals under our care as needed with antibiotics approved for use in chickens by the FDA.

(note this is a third-party transcript so may contain errors and differ from the actual speech in some ways)

Arguments like these are some of the reasons why I am less optimistic about total bans, rather than bans on subtherapeutic and growth promotion use of antibiotics. If there aren't good treatment alternatives available, then banning antibiotics outright would probably sometimes force producers to leave disease untreated, which seems like it would be really bad for animal welfare. I don't know how often there are no good treatment alternatives, but I'd guess it's some decent proportion of disease.

However, I do think the argument is a bit disingenuous. I can't find the transcript of that speech on Google so I don't know when it was made, but if it was before March 2019, Sanderson Farms was at that time using antibiotics not just to treat disease, but also to promote the growth of their chickens and prophylactically to prevent disease. Undoubtedly, using antibiotics in these ways has some non-negligable benefits to the chickens' welfare and to their environmental impact (although I don't know anything about the environmental impact of producing antibiotics!). But forgoing prophylactic and growth promoting antibiotic use would not force them to abandon their 'obligation to care for the animals under [their] care'. Also, it doesn't seem like people oppose using prescribed and targeted antibiotics, which is what the speaker was defending here. Both Tyson and Perdue sell antibiotics with the label 'No Antibiotics Ever', but Perdue reassures us in their FAQ:

"Of course, no matter how hard we try, some chickens will “catch something,” and we’ll never withhold appropriate treatment. Those chickens would not be labeled “no-antibiotics ever” and would be sold through different channels."

I'm therefore somewhat confident that even when producers do sell meat which is labelled 'No Antibiotics Ever' they still treat sick animals where antibiotics are the best treatment option. There is a strong economic incentive for them to do so, since mortality, slower growth rates, and worse feed conversion ratios are expensive. 

But of course, if any country were to totally ban antibiotics, they wouldn't be able to do this (I suppose it's possible they could export the animals needing treatment internationally, but this seems pretty unlikely). 

So, for a total ban to be net positive in my opinion, I would have to see strong evidence that a) welfare reforms were widely adopted and b) welfare reforms were effective at preventing disease, or c) antibiotic substitutes were equally effective at treating and/or preventing disease. I think this is a pretty high bar which isn't very likely to be met, so I would only be in favour of a ban on subtherapeutic/prophylactic and growth promoting use. 

This is exquisitely well-formatted. The section structure and use of the new table feature make this a textbook example of how to create an easy-to-read post. Thank you for putting it together!

Thanks for a great post!

Do you have any thoughts on how these kind of interventions compare to other alternative strategies to improve farmed animal welfare, in terms of effectiveness? For example compared to interventions to lower meat consumption generallty?

Thanks for your question!

I didn’t go as far as doing a cost-effectiveness analysis on this; I think that there are a lot of uncertainties that would make that quite difficult, but it'd definitely be a good next step for this topic.

My guess is that if we purely consider impact on animals then it might come out quite a bit less cost-effective than other interventions, but that if we account for public health benefits as well it might turn out to be comparable in terms of cost-effectiveness.

I think the two most important variables that cost-effectiveness would be sensitive to are whether/what kind of welfare adaptations farmers would make, and how effective antibiotic substitutes are. If we’re including impacts on humans then it would also be very sensitive to what proportion of the antibiotic resistance burden comes from antibiotic use on farmed animals!

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