One of the common issues with regard to backyard flocks relates to poor or inadequate feeding programmes that can lead to vitamin and mineral deficiencies for the birds. Vitamins and minerals are very important components of a chickens diet and unless a formulated ration is feed, it is likely that deficiencies will occur.

Poultry require all known vitamins except C. Some vitamins are soluble in fats, while others are soluble in water. Some of the symptoms of a vitamin deficiency are as follows:
Fat Soluble Vitamins
Vitamin A Decreased egg production, weakness and lack of growth
Vitamin D Thin shelled eggs, reduced egg production, retarded growth, rickets
Vitamin E Enlarged hocks, encephalomalacia (crazy chick disease)
Vitamin K Prolonged blood clotting, intramuscular bleeding
 
Water Soluble Vitamins
Thiamine (B1) Loss of appetite and death
Riboflavin (B2) Curly-toe paralysis, poor growth and poor egg production
Pantothenic Acid Dermatitis and lesions on mouth and feet
Niacin Bowed legs, inflammation of tongue and mouth cavity
Choline Poor growth, fatty liver, decreased egg production
Vitamin B12 Anaemia, poor growth, embryonic mortality
Folic Acid Poor growth, anaemia, poor feathering and egg production
Biotin Dermatitis on feet and around eyes and beak
Minerals are also important to the health and well-being of poultry. The following are some of the important minerals and symptoms of mineral deficiencies:
Minerals
Calcium Poor egg shell quality and poor hatchability, rickets
Phosphorus Rickets, poor egg shell quality and hatchability
Magnesium Sudden death
Manganese Perosis, poor hatchability
Iron Anaemia
Copper Anaemia
Iodine Goitre
Zinc Poor feathering, short bones
Cobalt Slow growth, mortality, reduced hatchability
As indicated above, vitamin and mineral deficiencies can produce numerous health problems for chickens including in some cases, death. Thus, to prevent nutritional deficiencies, or when deficiency symptoms are noted, feeding a balanced poultry diet with the required vitamins and minerals should be practised.