The short answers is not that many and they do not need much either especially if they are free range.
All supplements are the same, they are best used over a long period in small quantities. you can do as much harm as good by overdosing.
There is two reasons for this, the first is they find a lot of their own feed and prefer it this way. The second reason is they are not prolific layers like modern chickens that require huge amounts of calorific feed to produce eggs daily.
Below: Guineas Feeding.
If you keep your Guinea fowl confined or if you live in a place where there is snow and ice on the ground in winter then you will need to add a few bits and pieces to the diet to keep them healthy.
Below are things you can consider as additional supplements to improve the diet of captive guinea fowl:
1. Grit and shell:This is exactly the same mix you would give to chickens and the same size. It should be always available to guinea fowl regardless of how you keep them. It is important for digestion to help grind up food and for minerals like calcium.
2. Safflower seeds or sunflower seed kernels:These both have similar calorie and protein levels and are high in both. Guineas love whole seed scratch feed and these are a particular favourite of my birds.
Safflower seeds have a white shell and do not need to be bought shelled. Sunflower seeds on the other hand should be bough husked or with the shell removed.
3. Sprouts:You can sprout wheat, oats, barley, peas, millet, lentils or mung beans.
Sprouted seeds and grains are actually more nutritious than either feeding them whole.
You can feed as soon as they sprout or wait till they have produced a green shoot before feeding. The latter is especially beneficial in winter when natural greens may be in short supply.
4. Seaweed:Seaweed is loaded with trace elements and minerals and is a source of salts which are required in the diet but might be lacking in winter with no insect life around for them to feed on.
Dosage is 2g per bird per day. Just dampen the seed slightly and sprinkle over and the seaweed granules will stick to the seed.mix thoroughly.
5. ACV or Apple cider vinegar:This is a well known additive for chickens and it may be of some benefit to guinea fowl as well for the same reasons.
6. Powdered yeast extract:
This is a dry and powdered by product of the brewing industry. It contains masses of B vitamins and 18 amino acids. It also has the benefit of being 55% protein. B vitamins are all involved in the metabolism of carbohydrates, fats and proteins into usable energy and some are also important for digestion, immunity and red blood cell production within bone marrow.
Dosage: A little goes a long way and as with all supplements they are best added to foo and taken in small quantities over a long period. 2g per bird per day added to feed.
7. Food grade DE or Diatomaceous Earth:
Diatomaceous earth (DE) is a combination of silica, sodium, magnesium, iron and a mixture of other trace minerals. Dust the coop and nests or add 1 to 2 cups of DE per bag of feed for optimal health benefits:
- Can improve the quality of eggs if you are having shell problems
- Keep the feed pest free.
- Prevents internal and external parasites with regular use
- Make sure the birds have minerals available to prevent joint problems.
DE is not a magic treatment, it is mostly a preventative that with regular use has many benefits.
8. Flower petals:
Dandelions, Marigold or Sunflower petals. All contain natural colours than are known to be beneficial to the eyes and make bright yolks.
These are best grown yourself as they can be expensive to buy. Dry petals in the sun as the flowers are ready and store for whenever you need.
They can be bought.
9. Grated boiled egg:
For that protein boost when the birds are moulting. Moulting can be minimal or extensive and can happen gradually or fast. Feather loss can be extreme and added protein is the best solution. Feathers consist of about 85 percent protein, so big or fast moults can spell trouble.