Vitamin A

VITAMIN A

VITAMIN A (RETINOL, DEHYDRORETINOL)–Anti-infection vitamin

Sources

  • Green plants; fish liver oils
  • Carotene & Xanthene is converted to vitamin A in intestine

Storage

  • Liver (Kupffer cells) as RETINOL
  • adipose tissues
  • Blood as lipoprotein

Deficiency of vitamin A

  • Insufficient supply in ration
  • Chronic diseases of intestine
  • Liver diseases
  • Poisoning with chlorinated naphthalene interferes with conversion of carotenes
  • Increased phosphorous intake causes decreased vitamin A storage

Functions

  • Bone growth
  • Maintenance of epithelial surfaces
  • Night vision

Respiratory system

  • Ciliated columnar epithelium is transformed to stratified squamous epithelium

Reproductive tract

  • Sterility in bulls
  • Abortions
  • Retained placenta
  • Separation of maternal & foetal membranes

Urinary system

  • Transitional epithelium is converted to stratified squamous epithelium and may lead to formation of urinary calculi

Eyes – Xeropthalmia

  • No mucus secreting cells
  • Keratinisation of corneal and scleral membrane

PATHOLOGY

Night blindnes s (Nyctalopia)

  • Aldehyde

REVERSAL

Lesions in epithelial tissues

In gastro intestinal tract, respiratory tract, eye, skin, urogenital tract the epithelium is converted to keratinised, stratified squamous epithelium

  • Skin- Acanthosis; Rough, dry coat, bran like scales (Pityriasis) Horses- Cracks in hooves
  • Glands – Squamous metaplasia leading to obstruction and reduced digestion
  • Lips and tongue – Plaque formation
  • Bile duct and gall bladder – Cystic dilatation and pappilomatosis
  • Renal tubules –Hyperplasia leading to fibrosis
  • Male and female genitalia - Squamous metaplasia

Hyperkeratosis

  • Clinical signs
    • Lacrymation, anorexia, emasciation
    • Dry, rough , hairless, wrinkled skin
    • Fissures on skin
    • Stomatitis
  • Histopathology
    • Hyperkeratosis of stratified squamous epithelium
    • Metaplasia of ciliated columnar epithelium

Effect on bone growth

  • Retarded bone growth in young animals
  • Interference in growth of epiphyseal bone
  • Capillaries do not invade cartilage
  • No osteoblastic activity
  • Calves
    • No growth of skull
    • Brain grows causing herniation into foramen
    • Paralysis of skeletal muscles
    • Blindness ( pressure on optic nerve)
    • Encephalopathy
  • Birds
    • Defective bone growth
    • Hydrocephalous causes increased cerebrospinal fluid pressure

Nutritional roup in poultry

  • 1200-1600 1.U/kg of vitamin A included in ration of laying & breeders
  • 600 1.U in ration of chicks

Clinical signs

  • Adults
    • Emasciation, weakness, ruffled feathers
    • Decreased egg production
    • Decreased hatchability
    • Increased embroyonic malformations & mortality
    • Caseous material in eyes
  • Chicks
    • Chronic – 3 wks and more age
    • Decreased growth; poor feather development
    • Caseous material in eyes; nostrils
    • Nasal discharge; soiled feathers; paleness
    • Upper alimentary tract- pharynx, oesophagus
    • Plaque like or cheesy membrane
    • Small white nodules
    • Gout
    • Keratinisation of epithelium of ducts of glands
    • Metaplasia to stratified squamous epithelium
    • Occlusion of glandular ducts

Congenital anomalies

  • Dermoids in eyes of calves
  • Anoptholmos / Micropthalmos
  • Anasarca
  • Cleft palate
  • Malformed limbs

Last modified: Thursday, 22 March 2012, 8:12 AM