Chickens do not need any supplements in their drinking water providing they are well housed and fed properly. However, if you want to give them a little 'boost' or feel that they are lacking a bit of condition these additions are useful:

Apple Cider Vinegar:
Apple Cider Vinegar a completely natural and organic, anti-bacterial, anti-coccidial anthelmintic tonic which is packed full of vitamins and minerals and is a great worm preventative. It helps digestion and normalizes pH levels in the stomach. It increases egg production, improves feather quality and also flavor in meat birds. Apple cider vinegar also boosts calcium absorption from feeds - so if your hens are laying eggs with soft shells it can be used to try and make them harder. It can be mixed at the ratio of a table-spoon of ACV to one litre of drinking water (always check the instructions on the label).

Battles Poultry Tonic:
This is a general tonic which will give that little boost to your bird's health. It contains iron and phosphorus in a syrup base which also promotes appetite - keeping prime condition during their moult or the colder winter months. This can be given to chickens, ducks, geese, turkeys and so on. This can be mixed at a ratio of 2ml of tonic to one litre of drinking water (always check the instructions on the label) - so a single bottle goes a long way!

Shell Max:
This supplement promotes nutrient absorption to produce improved egg shell thickness and strength. It is used mainly for commercial flocks but breeders do give it to their chickens at breeding time to make sure the shells are healthy and not porous. Shell Max contains calcium and sodium bicarbonate and can be mixed at a ratio of 1ml of Shell Max to one litre of drinking water (always check the instructions on the label).