Studies of zinc nutrition in lambs with special reference to plasma bound zinc.

Abstract

The effect of feeding a severe Zinc deficient diet (0.9 mg Zn./Kg) to lambs was investigated by assessing performance, plasma proteins, plasma bound and unbound Zinc. Performance decreased, and results indicated an inability to adapt to the deficient conditions in six weeks. Food conversion was three to four times less efficient than in the control lambs, growth rate was significantly lower after three weeks, and food intake decreased in the first week. Rapid recovery of performance occurred when Zinc supplemented diets (40 mg Zn./Kg) were fed. External symptoms of Zinc deficiency showed some relation to plasma alkaline phosphatase activity which decreased during six weeks. Pin-prick sized haemorrhages were observed in the same week that enzyme activity decreased significantly. An explanation of the haemorrhages was suggested by reference to published work by the author. Total plasma protein concentration increased significantly each week. This was mostly due to a rise in globulin concentration, whilst albumin concentration was decreased. Both these proteins showed normal values after five weeks of feeding Zinc supplemented diets. This suggested that Zinc stimulated the synthesis of albumin, and inhibited the synthesis of globulins. Evidence was obtained to suggest that Zinc deficient female lambs had a more efficient mechanism than male lambs, of homocstatic regulation of plasma Zinc, beta1- and beta2-globulins. Evidence showed an interrelationship between total plasma Zinc, plasma protein bound and unbound Zinc. Protein bound Zinc in normal lamb plasma was located in albumin and beta2-macroglobulin. Evidence was obtained which suggested a possible homeostatic mechanism controlling bound and unbound plasma Zinc in Zinc deficient lambs. The amount of albumin bound Zinc decreased rapidly, whilst the beta2-macroglobulin bound Zinc was retained for a longer time. The amount of unbound Zinc remained relatively constant throughout. Therefore, the evidence suggested that albumin was releasing Zinc to maintain the proportion of Zinc necessary for physiological functions.

Date of Award	1976
Original language	English
Awarding Institution	University of Bath