Occurrence: Worldwide. Species affected: All. Age affected: All.

Causes: Deficiency of vitamin D3 in the diet.

Effects: Vitamin D3 is needed for proper Ca and P metabolism and in the formation of normal skeleton. Signs are therefore similar to Ca and P deficiency. Soft brittle bones (rickets) and retarded growth occur in young birds, whilst cage layer fatigue is seen in mature birds.

Vitamin D3 is needed for proper metabolism of calcium (Ca) and phosphorus (P), and in the formation of normal skeleton, hard beaks and claws, and strong eggshells. Rickets occurs in young birds and osteomalacia (cage layer fatigue) in mature birds.

A deficiency in the diet caused by variations in Ca and P content of animal by-products and variation in P bioavailability in various mineral sources. A phosphorus deficiency is common in cage layers which don’t have access to P in the faeces.

Postmortem lesions and histopathology (widening of epiphyseal plate, hypertrophy and softening of the bone, and irregular patterns of cartilage and bone development in the primary and secondary spongiosa) are diagnostic.

It simulates other deforming leg weaknesses in poultry.

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