Differential diagnosis
- Rickets


Etiology
- Calcium deficiency (in adult laying hens referred
  to as "cage layer fatigue")
- Vitamin D deficiency
- High level of dietary Ca (ties up P and renders it
  unavailable to the bird)


1. History taking
- Age of birds (adult laying hen)
- Calcium and phosphorus sources and ratio in feed


2. Clinical examination
- Signs of a deficiency of Ca or P, or both, in young
  growing birds are similar to those of vitamin D
  deficiency
- Stiff gait
- Retarded growth
- Ruffled feathers
- Rubbery beaks and leg bones
- Enlarged joints
- Thin-shelled eggs
- Low hatchability eggs
- No egg production
- If Ca is not supplied following paralysis, death
  follows within 1-3 days

3. Necropsy
- Cortical bones are thin


4. Feed analysis
Specimen : feed
Method : analysis of Ca and P levels by atomic
absorption spectrophotometry and colorimetry
- In both rickets and osteoporosis, ash content of
  the bones is decreased


5. Serum analysis
Specimen : serum
Method : analysis of Ca and P levels by atomic
absorption spectrophotometry and
colorimetry
- If dietary Ca is low, the blood level of Ca may be
  approximately normal, but the level of P may be
  increased due to the breakdown of labile bone
- Chemical chemistry : Increased alkaline
  phosphatase


Control and treatment
- A readily digestible Ca supplement is effective if
  started very soon after paralysis develops from Ca
  deficiency
- Diets contain adequate quantities of Ca and P