VITAMIN  A:

Vitamin A deficiency is characterized by poor growth, weakness, ruffled feathers, a drop in production and hatchability, and lesions in the digestive tract and eyes.

Causes:

1. Low level of vitamin A in the feed.
2. Oxidation of vitamin A in the feed.
3. Errors in mixing.
4. Intercurrent disease e.g; coccidiosis, worm infestation.

Control:

1. Use stabilized vitamin A in the poultry feed.
2. Add adequate levels of antioxidants in feed.
3. Regularly assay feed for vitamin A content.
4. Provide adequate storage for feed and feed ingredients.

VITAMIN  D:

Vitamin D deficiency is characterized by faulty utilization of calcium and phosphorus, resulting in skeletal abnormalities, and adverse effects on egg shell quality.

Causes:

1. Lack or inadequate amounts of vitamin D, particularly D₃ in poultry feed especially in confinment rearing.
2. Sulpha drugs in the feed may interfere with vitamin D absorption.
3. Vitamin D₂ is sensitive to oxidation and catalysed by minerals.

Control:

1. Add adequate levels of vitamin D₃ in the diet and assay of feed sample for its vitamin D₃ content at regular intervals.
2. The requirement of vitamin D₃ in the feed is related to the source of phosphorus and calcium, calcium and phosphorus ratio and exposure of chickens to sunlight.

VITAMIN  E:

Its deficiency in chicken is characterized by encephalomalacia (crazy chick disease), exudated diathesis (thin blood capillary), muscular dystrophy, low fertility and hatchability.

Causes:

1. Oxidation of fatty acids in the diet.
2. Errors in mixing.
3. Inadequate levels of vitamin E in the feed.
4. Use of propionic acid as grain preservative may lower the vitamin E content of the grains.
5. Inadequate Selenium levels in the feed.

Control:

1. Avoid excess fat in the diet.
2. Avoid the addition of rancid fat in the diet.
3. Add antioxidants in feed to prevent rancidity.
4. Provide adequate Selenium levels in the feeds.

VITAMIN  K:

Vitamin K deficiency in chickens is characterized by prolonged bleeding time or death due to bleeding from a minor injury.

Causes:

1. Inadequate levels of vitamin K in feed.
2. Loss of vitamin K potency during storage.
3. Presence of sulfa drugs in feed or water will interfere with vitamin K metabolic activities.
4. Prolonged administration of bactericidal chemicals which may destroy intestinal bacteria responsible for vitamin K synthesis.
5. Poor absorption from the intestine due to disease or dietary factors.
6. Low vitamin K in fertile eggs to meet the needs of dayold chickens.

Control:

1. Supply adequate levels of vitamin K in the feed.
2. Administer antibiotics and sulfa drugs with great care.