Introduction
The B complex vitamins are water soluble and not stored to any significant extent in the body. They act in a broad range of metabolic pathways. Simple deficiency is now rare as diets are usually well supplemented. However, because a continuous supply is required, damage to the intestine or increased demand for some reason may have an effect. Most will reduce productivity, including growth in the young animal, and egg production in the layer. The embryo is particularly dependent on having adequate supplies of vitamins deposited in the egg. Vitamin deficiencies are especially prone to cause problems of hatchability. See the separate discussion under Chondrodystrophy and Fatty Liver and Kidney Syndrome.
 
Signs
These may be summarised:
1) Perosis
2) Curled Toe Paralysis
3) Paralysis/'Stargazing'
4) Dermatitis/Scaly Skin
5) Mouth Lesions
6) Conjunctivitis
7) Anaemia
8) Fatty Liver and Kidney Syndrome
9) Poor Feathering
10) Loose feathers
11) Hatchability problems
12) Embryo with clubbed down
13) Thiamine (B1)
14) Riboflavin (B2)
15) Pantothenic acid
16) Pyridoxine (B6)
17) Niacin
18) Folic Acid
19) Cyanocobalmin (B12)
20) Biotin
 
Post-mortem lesions
Usually the gross lesions are non-specific.
Some deficiencies induce characteristic microscopic effects.
 
Diagnosis
Signs, exclusion of specific diseases, response to supplementation. If it is suspected that the vitamin premix may not have been included in the ration (or included at too low a level) it may be appropriate (faster, less expensive) to analyse feed for a marker substance such as manganese rather than testing for vitamin levels.
 
Treatment
If a specific vitamin deficiency is suspected, drinking water supplementation with that vitamin is ideal and usually results in a rapid response in birds that are still drinking. Good quality multivitamin solutions are beneficial in the supportive care of a range of problems characterised by reduced feed intake. The balance of vitamins present should be similar to the daily nutritional requirement of the stock concerned.
 
Prevention
Adequate supplementation of the feed with all required vitamins in levels which both support normal productivity but also have enough overage to deal with the increased demands that often occur during periods of disease challenge.