Zinc Deficiency

Introduction

Zinc is an essential component of many enzyme systems, including those related to protein and carbohydrate metabolism, and is essential for maintaining a healthy coat and skin.

Zinc is normally absorbed from the intestine at approximately 20-30% efficiency and competes with copper, iron and calcium for absorption.

Zinc deficiency may occur because of inadequate intake or availability, malabsorption or increased rates of loss from the organism.

Decreased zinc availability has been seen in certain dog foods containing excessive levels of phytate which inteferes with zinc absorption.

Zinc deficiency is mainly seen in dogs and pigs, sometimes in ruminants and horses.

Clinical signs

Pigs present with a disease called parakeratosis which appears as circumscribed reddened papules and plaques, thick crusting and scaling, fissures along ventral abdomen and medial thighs. Sometimes the condition is generalised and pigs may show mild lethargy, anorexia and depression. The skin lesions may resemble those caused by Staphylococcus hyicus however this usually occurs in younger piglets.

There is commonly secondary bacterial dermatitis which can complicate the diagnosis.

In dogs, a marginal deficiency may result solely in skin changes which are very noticeable to the owner. Zinc-responsive dermatosis is commonly seen in Siberian Huskies and Alaskan Malamutes and is characterised by scales and crusts around mouth, chin, eyes, joints, prepuce, scrotum and vulva.

In rapidly growing puppies, there will be scaly plaques on the skin, nasal planum and foot pads.

Canine zinc deficiency has also been described as producing ocular signs of mucopurulent exudation, blepharitis and keratitis.

Severe zinc deficiency will present as poor growth, anorexia, testicular atrophy and emaciation.

In ruminants, there is alopecia, crusts and scales on face, neck and distal extremities and mucocutaneous junctions. Low zinc status leads to lower quality milk and increased incidence of mastitis

In foals, zinc deficiency causes reduced growth rate, anorexia, cutaneous lesions on the lower extremities and alopecia.

Diagnosis

Clinical signs, skin biopsies and low serum levels of zinc and alkaline phosphatase will help to confirm a diagnosis.

Microscopically there is: in pigs: parakeratosis, acantosis, pseudoepitheliomatous hyperplasia, hypergranulosis

in dogs: diffuse hyperkeratosis extending to follicles, superficial perivascular dermatitis with eosinophils

Treatment

Pigs: zinc should be supplemented in the diet and calcium corrected in case it is affecting zinc absorption. Rapid recovery will follow.

Dogs: in fast growing puppies few a zinc-deficient diet or excessive calcium or phytates, zinc should be supplemented and the diet corrected.

In adult dogs such as the Husky and Malamute, zinc should also be supplemented and this may have to continue indefinitely to avoid relapses.

In ruminants, zinc supplementation can increase reproductive performance by increasing conception rate. There is also an improvement in hoof hardness and less white line disease.

Foals usually respond well to zinc supplementation.

References

Kahn, C. (2005) Merck veterinary manual Merck and co

Carlyle Jones, T. (1997) Veterinary pathology Wiley-Blackwell

Engelking, L. (2004) Textbook of veterinary physiological chemistry Teton NewMedia

Gelatt, K. (2000) Essentials of veterinary ophthalmology Wiley-Blackwell