INFLUENCE OF INORGANIC AND ORGANIC DIETARY ZINC ON ITS CONCENTRATION IN BLOOD-SERUM, BONES AND HAIR AND ON CATALYTICAL ACTIVITY OF SOME SERUM ENZYMES IN PIGS

The influence of dietary zinc originating from either inorganic or org anic source on zinc-depleted pigs was investigated. Within the 30 d pe riod preceding the trial, all the animals (German Landrace x Pietrain x Large White x Swedish Landrace weaned crossbreds) were depleted of z inc and divided into three groups, 14 animals in each. During the expe rimental fattening period (105 d), the control group received no extra zinc, whereas the two trial groups were fed a diet with zinc suppleme nt either as inorganic salt (ZnSO4) or metalo-organic chelate (zinc me thionate). On average, the respective supplements contained 84.3 mg Zn .kg(-1) diet and 40.9 mg Zn.kg(-1) diet. Evaluation of the nutritional effects of zinc was based on its concentration in the blood serum, bo ne and hair. Moreover, the effect of zinc on catalytical activity of a lkaline phosphatase, aspartate aminotransferase, alanine aminotransfer ase and gamma-glutamyltransferase in serum was studied. A decrease of catalytical activity of both aspartate aminotransferase and alanine am inotransferase was found along with signs of parakeratosis on the skin of control animals but no correlation with serum zinc was established . In contrast to this finding, a linear correlation between catalytica l activity of alkaline phosphatase and of gamma-glutamyltransferase an d serum zinc level was found with the respective correlation coefficie nts of 0.90 and -0.72. Nutritional efficiency of diet zinc was evidenc ed by both higher (P < 0.05) zinc level in blood serum, bone and hair and by the state of hepatobiliary tract and bones, and favourable perf ormance results of trial animals compared to controls. None of trial a nimals suffered from any health disturbances. Progressive parakeratosi s appeared, however, in control animals and lasted during the second m onth of the trial. It was accompanied by deterioration of performance data of the affected animals. Our data suggest that bioavailability of zinc from the chelate was better than of that derived from inorganic salt, particularly in the period of rapid growth. This presumbaly resu lted in reduced elimination of zinc. Based on better nutritional effic iency in pigs and on ecological benefits, zinc methionate should be pr eferred to ZnSO4 as a zinc containing diet additive.