Surplus nutrients are converted into fat
It’s not easy to put a chicken on the right diet yourself. Feeding a commercial diet which is specifically formulated for the age/type of poultry being fed is usually the safest path to follow.
Things can easily go wrong if you’re supplementing this relatively expensive food with cheaper ingredients such as household or garden scraps, or cheaper whole grains etc. This can mean a balanced diet becomes imbalanced in terms of protein and energy, so the birds begin to compensate by eating more of one ingredient than they need in order to try and get enough of what is short.
For instance, if you substitute half of a commercial layer diet with cheaper wheat, which is much lower in protein, the birds will only be getting about three-quarters of the daily nutrients they require. To compensate, they will eat more of the available food in an effort to gain the right amount of protein or energy. Surplus other nutrients are then converted into fat. Supplementing a balanced diet may save you a bit of money, but there are other costs. For example, hens will not lay to their potential if their bodies are not receiving sufficient nutrients to maintain reproduction and maintenance. If the birds are on an adequate free range with plenty of insect life around, they may do reasonably well, but if they are confined to a small bare earth run or a new patch of lawn each day, their health may be compromised, especially if the feed quantities on offer are restricted.
Bulking out part of the diet with kitchen scraps or vegetable peelings has the same effect. The nutrient level of these foods will not be what birds need, and because this kind of diet is usually high in energy and low in protein, the birds will eat more and store away the extra energy as fat, both around the abdominal organs and in the liver. In a heritage breed, especially a large breed, the extra carbohydrates may not matter, but it may still have an effect,
can be high in phosphorus, which then unbalances the calcium-phosphorous ratio, essential for proper bone and egg shell manufacture.
Another shortfall in this type of multi-species feed is that because it is primarily intended for ruminants, the vitamin/mineral premix in it is not likely to have choline chloride added. It is also debatable as to whether other vitamins – A, B, D, E and K – will be in it at a level essential for poultry. Even a balanced, complete poultry feed which is only missing choline can result in fatty liver syndrome in the birds which eat it.
Finally, another possible cause of fatty livers can be aflatoxins. These are the toxic metabolites produced by moulds and fungi which can contaminate feed and damp litter materials. Some feeds are particularly prone to allowing mould growth when damp so the manufacturers add molasses as a key ingredient. Copra, the dried flesh of coconut after the oil has been extracted, is often used in the feed manufacturing industry and is known to have a high level of aflatoxins.