You've probably read about apple cider vinegar (ACV) on chicken-keepers' blogs. It's claimed to cure everything from cancer to smelly poop.
But in some places, it's banned altogether as an unsubstantiated claim which is no more than an untested "folk remedy".
So which is it?
In this article, I look at the scientifically-based evidence (see sources) for and against using natural apple cider vinegar for chickens' health.
Whether or not you then decide to use it is a matter for you.
But at least you will have proper, factually-based information to make that decision rather than enthusiastic but anecdotal individual opinions.
What is organic Apple Cider Vinegar and why use it?
It's basically fermented apple juice. It's been used by ancient cultures for thousands of years, both in cooking and for its health benefits for humans. These days people make many claims for its use, from helping weight loss to improving digestion and beyond.
Using antibiotics in livestock has been regarded as a risk by the World Health Organisation and the Food and Agriculture Organisation for decades. It's known that over-use of antibiotics has caused antibiotic resistant bacteria to become part of everyday life.
It's critical that their use is severely limited. In Europe, antibiotic use in livestock rearing has been banned since 2006. Other ways to combat illness and in particular bacterial diseases had to be found. That led to research for natural alternatives.
Apple cider vinegar was found to be one such alternative.
The apple cider vinegar you see in your local supermarket is likely to be pasteurised. The process of pasteurisation kills helpful bacteria. So it doesn't offer the same health benefits.
You need to look for natural, organic, unpasteurised ACV. It's this raw, unprocessed type that contains the "mother". The "mother" develops during fermentation and is the source of its probiotics - good bacteria - along with vitamins and minerals.
Braggs is one of the most well-respected brands of organic apple cider vinegar.
How to tell the difference?
You'll see statements all over poultry blogs and websites about ACV curing more or less everything. Most of it is purely anecdotal - "it must work because I give it to my chickens and they've never had worms / mites / diarrhea / respiratory problems..."
But then a lot of other people have never used it, and their chickens haven't had any of those things either!
Some of the supposed benefits I've seen listed for chickens are:
It's really not good enough to make claims for anything without evidence that's been properly tested.
Some of these things are nonsense and could cause real problems if taken seriously. Mites, for example, are not "put off by the bad taste"! And the "mucous" studies refer to is nothing to do with the respiratory system. It relates to the gut - that's a serious misunderstanding by some bloggers.
Not dealing with either of these things appropriately can lead to serious illness and even death.
Be realistic. Do not expect a dose of ACV to cure most of the things you'll see it promoted for!
Here's what studies have found apple cider vinegar is a specific benefit for.
It's been known for some time that the bacteria which cause coccidiosis in chickens have become increasingly resistant to drugs. That, together with the public's increasing concern about antibiotics in meat meant the poultry industry have recently invested in searching for alternatives.
They found one in apple cider vinegar (always with the mother).
Recent research studies (1, 2) have demonstrated that chickens given apple cider vinegar in their drinking water "significantly increased" the percentage of beneficial antioxidants and "significantly decreased" the level of harmful toxic stressors in cells.
The result: "In the vinegar group, no clinical signs of coccidiosis were observed. In two control groups, chickens showed clinical signs of coccidiosis... and the number of coccidial oocytes in feces increased over time".
Other studies, using both adult chickens(3) and one day old chicks followed through to adulthood(4), have demonstrated the effectiveness of ACV against other bacteria, specifically salmonella, campylobacter and escherichia coli (e-coli).
In eliminating those "bad" bacteria, it also "enhanced the specific and non-specific immunity in poultry".
Because ACV reduces harmful bacteria, it at the same time allows nutrients in the gut to increase. The gut is no longer having to share nutrients with the bacteria.
What studies (3, 4) show is that the gut itself then improves. The surface area of the intestine (the "villus") increases, the "intestinal mucosa" which helps preserve the gut's ability to absorb nutrients becomes less inflamed, and the chicken is able to absorb more of her food's nutrients as it passes through the digestive system.
This is where the misunderstanding about ACV having benefits for the respiratory system happens. People have seen some of these studies but not understood the terms or the science. Here, the word "mucous" doesn't have anything to do with the chicken's breathing. It's the "mucosa" in the intestine that sees an improvement.
You'll see many sources online saying that apple cider vinegar prevents chickens absorbing calcium, which of course is vital for egg-laying hens.
You'll see others saying it aids calcium absorption. Sometimes, you'll see both statements in the same article - even in the same paragraph.
The most recent study, conducted in 2021(6), demonstrated that ACV provides an increase in the intestine's ability to absorb nutrients, including calcium.
The most important message here is that over-use of ACV causes the problems. Staying within the recommended dosage, and providing additional calcium for your hens, is unlikely to have an impact.
This is important for the broiler chicken industry where birds are expected to put on growth very quickly.
For our backyard chickens, it's clearly a benefit - we want our chickens to reach their full potential - but it's not the most important effect of ACV. The more important benefit is the control of harmful bacteria.
One study(5) demonstrated that egg production in hens given apple cider vinegar "significantly increased" between the ages of 24 and 28 weeks, compared to a control group not given ACV.
The difference was not found to be statistically significant at other ages.
You may see opinions on blogs or in forums which state that claims for ACV benefits are grossly exaggerated - and they're right.
What's not correct is to claim that because studies all rely on broiler chickens, they should be discounted for backyard flocks. Yes, broilers are different (and for the record, I don't advocate raising broilers. They have immense problems because they're bred to grow to a massive size very quickly).
But a chicken's digestive system is the same whichever type you're talking about. And that's where most of the benefits are.
There is a study(7) which suggests that there was no impact from adding ACV to water, but the test conditions between that study and others were different - and this is an old study. A lot more research has been done since that time because of the need to reduce antibiotic use.
There is, though, evidence that:
It's pretty simple to make your own ACV with the mother, but it's not expensive to buy and, at the rate it should be used, a bottle lasts a long time!
Home produced also tends to have less acidity than the carefully controlled commercial brands. And if it's not done properly, mould can form, so it will need to be thrown away.
The best source I've found is Braggs. It's organic and unpasteurised, so it contains the mother, it's gluten free and it's a well established brand, having been in business since 1912.
It also has the advantage of being 5% acetic acid concentration, which is exactly the level research suggests.
Fermenting feed for chickens is an excellent way to boost their immune system, keep disease at bay and help them lay eggs with stronger shells.
These two articles describe (left) the benefits of fermentation for chickens, based on research findings and related to our backyard flocks; and (right) exactly how to go about making fermented chicken feed in four easy steps from choosing the right containers and the right food to exactly what to do, day by day.
A lot of "facts" you'll find on the internet are often people's individual views, based on inaccurate information repeated from poor quality sources.
The information I provide in this article and others is based not just on my own experience, but on evidenced facts from scientific, peer-reviewed research and highly respected and experienced poultry keepers such as Gail Damerow.
Some of the sources I have used in this article are these. They're by no means the only ones - you'll find many others by doing a simple search.
1. Firas, F.M.F. Hayajneh et al: Anitcoccidial Effect of Apple Cider Vinegar on Broiler Chickens: an Organic Treatment. Pub. Polish Journal of Veterinary Sciences, 2018.
2. Quiroz-Castaneda, R.E. and Dantan-Gonzalez, E.: Control of avian coccidiosis: future and present natural alternatives. Pub. BioMed Research International, 2015.
3. Khan, S.H. et al: Recent advances in the role of organic acids in poultry nutrition. Pub. Italian Journal of Animal Science, 2015.
4. Allhardo, P. et al: Effect of probiotic and vinegar on growth performance, meat yields, immune responses and small intestine morphology of broiler chickens. Pub. Italian Journal of Animal Science, 2018.
5. Dhawale, A: Better eggshell quality with a gut acidifier. Pub. Poultry International, 2005.
6. Jahantigh, M, et al: Effects of dietary vinegar on performance, immune response and small intestine histomorphology in 1 - 28 day broiler chickens. Pub. Journal of Veterinary and Medical Science, 2021.
7. Kubena, L.F: Effects of Drinking Water Treatment on Susceptibility of Laying Hens to Salmonella Enteriditis During Forced Molt. Pub. Journal of Poultry Science, 2005.