The addition of zinc sulphate to the sole drinking water source of 3 groups of 5 cattle at concentrations of 0.25, 0.5, and 1.0 g Zn/l reduced water consumption by 8, 35, and 54 respectively ofcontrol (no added Zn) intakes overa 9-week period. The effect was greatest over the early weeks of the experiment. Moderate pancreatic damage was recorded in all 5 animals of the high Zn treatment group. Mild pancreatic lesions were seen in 2 animals of each of the other 2 Zn-supplernented groups. Group daily mean Zn intakes ranged from 12 mg Zn/kg for the low Zn group in the first 3 weeks to 45 mg Zn/kg for the high Zn group in the last third of the experiment. In the latter group the mean daily intake varied from 0 to 75 rng Zn/kg. Water consumption fell sometimes to zero in all groups after rain or a new allocation of fresh pasture, indicating that drinking water may be an unreliable method of administering Zn. It appeared that the unpalatable nature of aqueous Zn solutions was insufficient to prevent toxicity. The effect of Zn on water consumption may adversely affect production if concentrations as high as these were used for the attempted control of facial eczema in dairy cows.
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