Comparison of dietary hydrated copper sulphate, dietary zinc oxide and a direct method for inducing a moult in laying hens.

Abstract

The experiment lasted for seven 28-d periods. Laying hens of two breeds were allocated to 10 treatments. For the first 28-d period all birds were offered the control diet and then the following dietary treatments applied: a control group not moulted, one group moulted traditionally, 4 groups moulted using CuSO4- and 4 using ZnO-containing diets. After the moulting treatments the hens were offered the control diet for the remainder of period 2 and for a further five 28-d periods. The treatments applied during period 2 significantly reduced food intake, body weight, egg number, total egg weight and efficiency of food conversion. On returning to the control diet, there were no significant differences in cumulative food intake (periods 3 to 7). Body weight had returned to the same value as the control group by the end of period 3. Dietary treatments significantly reduced the efficiency of food utilisation during periods 3 to 7 and 1 to 7 inclusive. For periods 1 to 7 inclusive the birds force-moulted using CuSO4 and ZnO gave on average greater egg numbers and total egg weights than those moulted traditionally. The Haugh unit score was significantly improved after moulting. Egg Zn concentrations were increased by the 14-d ZnO treatments. The use of a diet containing CuSO4 (2 g added Cu/kg for 7 d) was as effective as one containing ZnO (20 g added Zn/kg for 14 d) and both were superior to a traditional force-moulting technique.