EFFECTS OF ZINC-DEFICIENCY AND APPLICATIO N OF EXOGEN RECOMBINANT BOVINE GROWTH-HORMONE ON PERFORMANCE AND PARAMETER OF ZINC STATUS OF CALVES

In a fifteen week breed- and a ten week fattening experiment both a co ntrol group and a zinc deficient group were treated with exogen bovine growth hormone. For that purpose 48 male Brown Swiss calves were dist ributed to four treatments and housed in individual boxes. The animals of the breed experiment maintained a milk replacer for the first seve n weeks with a zinc content von 6.7 mg/kg and for the whole experiment a basal diet with 7.8 mg zinc/kg. The zinc content of the milk replac er in the fattening experiment was 5.7 mg zinc/kg. Blood samples were taken in the weeks 1, 7,13 and 15 in the breed experiment and in the w eeks 1, 5 and 10 in the fattening experiment by puncture of the jugula r vain using the vacutainer system. The daily weight gain of the zinc deficient groups decreased about 20-25 % in comparison with the contro ll groups. The daily weight gain of groups treated with growth hormone amounted also to 21-24 %. The feed conversion rate decreased 38 % res pectively 20 % for the not with growth hormone treated animals and abo ut 35 % respectively 32 % for the treated animals. The zinc content of the plasma was reduced about 80 % in the breed- and 84 % in the fatte ning experiment. Zinc binding capacity increased about 17% in both exp eriments. The activity of the alkaline phosphatase decreased about 75% because of the zinc deficiency. The application of the exogen growth hormon increased the daily weight gain about 14 % and 13 % for the hig h with zinc maintained groups and about 15 % and 14 % for the zinc def icient animals. The feed conversion rate raised 11 % in the breed expe riment respectively 18 % in the fattening experiment for the high with zinc supplied animals and about 12% respectively 9 % for the zinc def icient animals. These results show that the decrease in daily weight g ain, feed coversion rate and change in the parameter of the zinc statu s of the deficient animals are not able to be compensated by the treat ment with exogen growth hormone. A reduced concentration of growth hor mon is not causal for the derailments of the metabolism in zinc defici ency.