STUDIES OF ZINC NUTRITION IN SHEEP .I. RELATION OF ZINC TO GROWTH TESTICULAR DEVELOPMENT, AND SPERMATOGENESIS IN YOUNG RAMS

Ram lambs fed on a diet containing 2-4 p. p. m. zinc made poor growth, developed clinical signs of severe zinc deficiency, showed impaired testicular growth, and showed a complete cessation of spermatogenesis within a period of 20-24 weeks. Lambs fed on the same diet supplemented with zinc sulphate to provide total zinc levels of 17-4 and 32-4 p. p. m. had a higher feed intake, made significantly greater liveweight gains, and showed no signs of zinc deficiency. Testicular growth and sperm production were markedly improved by both the zinc supplements. No differences in liveweight gains or feed consumption between the two supplemented groups were observed but testicular growth and sperm production were highly significantly greater in the lambs receiving the larger zinc supplement. It was concluded that a dietary zinc intake of 17.4 p. p. m. is adequate for growth of ram lambs but is inadequate for normal testicular development and function. Lambs in which consumption of the diet containing 32-4 p. p. m. zinc was restricted to that of the zinc-deficient group showed no significant improvement in liveweight gains, but testicular development and sperm production were significantly greater than in the zinc-deficient lambs. Complete remission of all signs of zinc deficiency and full recovery of testicular size, structure, and function were achieved in a zinc repletion period lasting 20 weeks. © 1969 CSIRO. All rights reserved.