The zinc requirements of broiler chicks and turkey poults fed on purified diets.

Chicks and turkey poults were fed for 3 weeks on low-zinc diets, prepared from purified ingredients, supplemented with zinc oxide at graded levels. Birds of both species given the unsupplemented basal diets grew poorly, with high mortality rates. All had severe hyperkeratosis but bone development was normal. Only when birds received diets with low concentrations of added Zn were leg abnormalities observed. Zn requirements were assessed visually from dose-response graphs. The chick required 18 mg Zn/kg diet for maximal live weight and 24 mg Zn/kg for maximal Zn concentration in blood serum. The responses of tibial Zn and net retention of Zn did not reach plateaux within the range of dietary Zn concentrations studied. The turkey poult's Zn requirement for maximal live weight was 25 and 28-29 mg/kg for net retention of Zn and for maximal concentration of Zn in blood plasma and in the tibia; 41 mg Zn/kg diet was required for maximal Zn in blood serum. Liver Zn was not correlated with dietary Zn in either species.