Influence of protein intake on per os zinc deficiency treatment in sheep.

Two experiments were conducted on 20 male 3.5 month-old Limousin X Romanoff lambs, weighing between 30 and 35 kg. They received a zinc deficient diet based on 50% late harvested hay and 50% barley straw containing from 8 mg Zn/kg dry matter to 11.7 mg Zn/kg dry matter and sprayed with caramel. Sheep were hypozincaemic from the 14th or 21st day. In the first experiment, the zinc level of the diet (94 g crude protein/kg DM from urea) was increased to 50 mg Zn/kg dry matter on the 35th day. At the same time, half the animals received egg albumin instead of urea; both diets were isoproteic. No change in zincaemia was observed in either of the two groups: it remained low. On day 51, the albumin group received an increase in dietary protein by the addition of more egg albumin, so that the diet contained up to 148 g crude protein/kg dry matter, the usual requirements of growing lambs. The zincaemia of these sheep started to increase and was restored to normal with a diet that contained 150 mg Zn/kg dry matter. The zincaemia of the low protein group remained unchanged whatever the zinc level. In the second experiment, increasing the zinc level with the diet (70 g crude protein from egg albumin) from 11.6 to 300 mg/kg dry matter restored the zincaemia either in the high protein group (140 g crude protein/kg dry matter) or in the low protein group (70 g crude protein/kg dry matter).(ABSTRACT TRUNCATED AT 250 WORDS)