Rations Suplemented with minera's mixture (Mn, Zn and Cu), iodine or desiccated thyroid were fed to 8 weeks old Dokki-4 cockerels to study their effect (fiom 8 to 24 wceks) on the reprod uotive capacity of males. The effect of age on the same criteria was also detrmin d. It was proved that the mentioned microadditives favoured the sperm count per gra me tisticular tissue at 20 and 24 weeks of age. Also, it was detected that the contents of such trace elements, at the same ages, were higher in the testes of the treated chicks rather than in those of their controls. It was possible to diagnose spermatozoa as early as 12 wieks of age. The daily rate of sperm production was 4.41 x 109 sperm at 24 weeks of age. Semcn was collected from the vase defer n'ia of many cookerels at 20 and 24 weeks of age with average con centrations of 4.28 and 8.87 x 104 spermatozoa/mm3 at the two ages respectively.