Vitamin- D deficiency

Animals obtain vitamin D either through the diet or when skin is exposed to solar radiation. The deficiency of vitamin D is associated with reduced absorption of calcium and phosphorous from intestine and is manifested by poor appetite, reduced growth, and osteodystrophy in advanced state.

Aetiology: Lack of ultraviolet solar irradiation of skin coupled with low levels of vitamin D in diets causes deficiency of vitamin D. Cloudy, overcast sky, atmospheric smog, winter period and indoor housing predispose the deficiency of the vitamin. Rapidly growing young animals and animals with dark skin and heavy coats are first to be affected by poor irradiation. Grass ensilage contains very little vitamin D and its continuous feeding may enhance chances of vitamin D deficiency. Lush green feeds, including cereal crops are reported to possess anti-vitamin D potency due to presence of large quantities of carotene and some other rachitogenic factors and can predispose deficiency of the vitamin.

Clinical findings: Vitamin D deficiency in farm animals is marked by reduced productivity and poor weight gain due to decreased appetite and food utilization efficiency. Reproductive performance is decreased. Lameness in the forelegs is noticed in late stage. In young animals, lameness with bending of forelegs and swelling of joints are seen. The rickets in young animals and osteomalacia in adult animals can be seen simultaneously in vitamin deficient herds.

Diagnosis: Vitamin D deficiency is diagnosed by probabilities of the presence of causative factors and response to vitamin D treatment. Laboratory findings include  hypophosphataemia in early stage. Plasma vitamin D values are also useful to detect vitamin D deficiency.Necropsy findings indicating rickets in young and osteomalacia in adult animals, and analysis of feed samples also aid in establishing diagnosis.

Treatment and prevention: Primary treatment includes correction of diet so that affected animals receive adequate vitamin D, calcium and phosphorous in the diet. Cholecalciferol (Vitamin D3) is used either parenterally or in the diet for treatment and prevention of rickets and osteomalacia. The doses of cholecalciferol in cattle,sheep, calves and lambs are — 9.40-31.25 mg, 6.25-12.5mg, 6.25, and 3.125 mg, respectively by subcutaneous or intramuscular rout.  Oral preparations of vitamin D are also available for treatment of vitamin D deficiency. Precaution should be taken while using vitamin D therapy as excessive parenteral doses of vitamin D (15-17 million IU in cattle) may cause prolonged hypercalcaemia, hyperphosphataemia, high concentration of vitamin D in plasma, and signs of toxicity including anorexia, weight loss, dyspnoea, tachycardia, torticollis, fever and death. Calcification of walls of blood vessels has been reported in cattle receiving 10 million units of vitamin D per day.A daily intake of 7-12 IU vitamin D per kg body weight is recommended to prevent deficiency. Vitamin D should be supplemented in diet or given parenterally when exposure to sunlight is inadequate and diet is deficient of natural sources of vitamin D.

Animals raised indoors and on diets with inadequate vitamin-D, for example calves on milk, pigs on grain and cattle not receiving sun cured forage, usually need dietary supplementation of vitamin D. Sun dried hay is a good source of vitamin D. Single parenteral administration of vitamin D2 (Calciferol) @ 11000 units per kg body weight
protects ruminants for 3-6 months.