Special Veterinary Pathology

VITAMIN D

VITAMIN D (ANTI-RACHITIC FACTOR)

• Provitamins of vitamin D- Ergosterol in plant tissues and 7-dehydrocholestrol in animal tissues
• Endogenous synthesis of vitamin D in skin
• Dietary supplementation
• D₂ or calciferol- uv light on ergosterol
• D₃ or cholecalciferol- UV light on 7- dehydrocholesterol
• Mechanism of action

Sources

• Fish liver oil
• Exposure to sun
• Sun cured hay

Functions

• Absorption of Ca from the intestine
• Increased serum Ca & P levels
• Mineralisation of bones

Causes for deficiency

• Lack of irradiation of skin
• Winter months in cold countries
• Animals kept indoors
• Places with smoke screen
• Furry skin coats
• Diseases of liver and intestines
• Increased feeding of lush green feed leads to excess of vitamin A which has anti –vitamin D activity

PATHOLOGY

Rickets - Young animals

• Stunted growth
• “Bowed legs”
• Pot bellied appearance
• Kyphosis
• Scoliosis
• Enlargement at the ends of bone & joints
• Bending of benees
• “Ricketty- Rosary”
• Enlarged costo-chondral function
• String of beads
• Crooked sternum in birds

Osteomalacia or adult rickets

• Occurs in animals in which endochondral
• Ossification ceased
• Increased bone resorption causes atrophy of bones
• Compact bones becomes spongy
• Fractures and deformities common
• No calcification

Poultry

• Decrease egg production;decreased hatchability
• Thin shelled eggs
• Pliable beak
• Bending of keel bone

Milk fever

• Following parturition in cows, ewes, sows goats, bitches
• Sudden hypocalcemia
• Maternal calcium drained to fetus
• High milk yielding cows increased calcium excretion in milk

Hypervitaminosis D

• Hypercalcemia and Hypercalcuria
• Metastatic calcification
• Renal damage
• Osteoporosis due to osteoclastic activity