Many commercial chicken feeds contain some form of chemical supplement to boost the immune system.
And both commercially farmed and some backyard flocks are systematically given antibiotics to guard against disease.
There are two issues with this: chickens should never be kept in conditions where they need antibiotics as a matter of course. Basic good husbandry should be enough to ensure disease is uncommon.
And secondly, the use of some natural substances is a far better option to help boost the chicken's immune system before drugs become necessary.
It's not difficult to protect your chickens naturally, without recourse to commercially produced additives. Because one of the most common and easiest to grow of all garden flowers blends both those qualities - and more.
The humble marigold.
There are several different types of plant which carry the "umbrella" name of marigold, but are different both in looks and in the jobs they do.
Proper research (see my sources section) shows that not all of them have the properties we're looking for to keep our chickens healthy.
It's important to understand the differences; otherwise, you'll give your chickens the wrong type of genus and wonder why you're not getting the results you were aiming for.
The dwarf version of each of these plants has the same qualities as the standard.
Top Tip: When shopping for marigolds, search by the botanical (Latin) name, not the common English names which are sometimes confused.
Often known by its Latin name, calendula, as well as marigold, this is an easy one to distinguish with its brightly coloured orange or yellow flower head and its daisy-like petal formation.
The calendula is a perennial plant but can't survive hard winters, so in many colder areas it's thought of as an annual which needs replacing each year.
The calendula has anti-bacterial properties and is best used in eco-friendly cleaning washes for the coop.
This is the variety seen most often in gardens and hanging baskets. It comes in various colours, the most popular being a deep orange and bright yellow.
An annual plant, it tends to spread rather than grow upright and blooms from summer up till first frosts. It's fine with rainy conditions too, so not as good for very dry climates. Water often!
This is the plant you want if your aim is to make your hens' eggs a darker shade of orange, and add to their nutritional value.
With a flower head like a pom-pom, the African marigold, sometimes known as the Mexican, can grow up to 90 cm (35") tall. Its height makes it a favourite of florists for adding elevation to displays.
It survives well in drought, too, so if you often forget to water your plants this is a good choice!
This is perhaps the most amazing of the family. It's a rich source of carotenoids which are known to have antioxidant effects, improving general health and helping strengthen the immune system.
Through scientific research, we know that marigolds contain high levels of flavonoids and the carotenoids lutein and lycopene.
Each of these is a powerful antioxidant.
Antioxidants are an important factor in keeping any living creature healthy. They prevent normal cells being destroyed by "free radicals" which, left to their own devices, break the healthy cells down, leading to illness and disease.
There have been a substantial number of studies(e.g. 1, 2) showing that using both marigolds and marigold extract in the poultry diet increases the chicken's antioxidant capacity and helps repair skin tissue.
In other words, marigolds help chickens ward off disease.
The best marigold for this is the African / Mexican, tagetes erecta.
Don't use essential oils here. The extract used in scientific studies is specially prepared, extracting the carotenoids directly from the flowers and having a specific lutein content(2).
As well as helping a chicken's health, the carotenoids present in marigolds also affect egg quality - in a good way.
In fact, the cholesterol level was found to have decreased by a massive 29.98%(2).
So there are benefits not only for chickens and their eggs, but for us, too.
Want to know more about eggs and cholesterol? Here's my article.
Tagetes erecta (the African or Mexican marigold) was found to have the highest level of carotenoids, so if your main aim is to reduce cholesterol in your eggs, this would be the family to go for.
Most people these days prefer a rich, dark coloured yolk in their egg. To deal with this market demand, many egg producers add synthetic pigments to their hens' feed.
But there are questions over the safety of those pigments(5).
And there's no need to use them. Add marigold flowers instead for natural enhancement of yolk colour.
Any of the tagetes varieties will help with this. However, the French marigold (tagetes patula) is known to show particularly good effects(4).
Chickens are particularly attracted to red, orange and yellow colours so persuading them to eat marigolds isn't difficult. Except, of course, that chickens can be picky.
Don't worry too much about the amount, though. Studies have shown no adverse effects even when the addition of marigolds or marigold extract was high(1).
Is using marigolds to keep mosquitoes and other bugs at bay based in fact or myth?
It's a scientifically proven fact(4) - if you have the right kind of marigold. The correct plant to use here is the tagetes patula variety - the French marigold.
This genus of marigold plant contains pyrethrum, a chemical it gives off during its normal growing cycle. Pyrethrum is toxic to many insects - if you look at the make-up of most insecticides, you'll find it as one of the ingredients.
So it's one of the best holistic insect repellents, as well as its radiant flowers attracting butterflies and bees who love to pollinate it. The best of both worlds - and much better to try a marigold repellent than chemical compounds.
Plants work best, but because chickens love them too it's best to use a raised planter or hanging basket outside your coop door.
Make sure the marigold you buy is a scented variety.
The flowers of the common or pot marigold (calendula officinalis - not the tagetes genus) is proven to have anti-bacterial properties, effective against fungi and bacteria(5).
So it makes sense to use them as an eco-friendly anti-bacterial wash in your coop. It will not get rid of an established infestation of lice or mites, for example, but using it to clean the coop as a normal part of weekly husbandry will help control outbreaks from happening in the first place.
A wash for walls.
An oil based mix for surfaces.
Again, it's the common marigold, calendula officinalis, which has anti-bacterial properties. But is it of any use in nest boxes?
I've seen claims around the internet that marigold petals scattered in nest boxes work all kinds of miracles, from clearing respiratory diseases to getting rid of tumours.
Those claims are unfounded. As we've seen, for marigolds to have any medicinal effect, they need to be ingested.
Does it hurt to scatter marigold petals in your nest boxes? Of course not! The hens may eat them, which is a benefit, and they'll look pretty.
If you don't want to go to the trouble of drying them yourself, dried calendula flowers are easily obtainable online.
Of course, you can buy marigolds at any garden centre but they're so much less expensive to grow your own - and more fun.
And remember that not all bought plants have been grown organically. Be sure they have been raised without insecticide spray.
All types of marigold are so easy to grow in virtually all types of soil that they make a great project for kids. And their strong colours make them a favourite to brighten any display, whether in the veg patch, the border or in pots.
Sow the seeds as soon as frosts have passed. The African marigold is slower to mature than others, so start with that variety - or buy young plants rather than seeds.
They do prefer full sun, so bear that in mind when you're planting out.
Remember: as well as marigolds being good for your chickens, your eggs and your coop, they're also a great addition to the garden to attract honey bees and butterflies.
1. Wang, S., et al: Effects of dietary marigold extract supplementation on growth performance, pigmentation, antioxidant capacity and meat quality in broiler chickens. Pub. Journal of Animal Science, 2017.
2. Nuraini, M., and Djulardi, A.: Marigold flower extract as a feed additive in the poultry diet. Pub. International Journal of Poultry Science, 2017.
3. Baker, R., and Gunther, C.: the role of carotenoids in consumer choice and the likely benefits from their inclusion into products for human consumption. Pub. Journal of Trends in Food Science and Technology, 2004.
4. Lokaewmanee, K. et al: Enhancement of yolk color in raw and boiled egg yolk with lutein from marigold flower meal and marigold flower extract. Pub.
5. Liu, G., et al: Skin pigmentation evaluation in broilers fed different levels of natural okra and synthetic pigments. Pub. Journal of Poultry Research, 2008.
6. Moore, S. J. and Maia, M. F: Plant based insect repellents: a review of their efficacy, development and testing. Pub. Malaria Journal, 2011.
7. Efstratiou, E et al: Anitmicrobial activity of calendula officinalis petal extracts against fungi. Pub. Jpournal of Complementary Therapy, 2012.
8. Bloom, J: free Range Chicken Gardens. Pub. Timber Press, 2012.