Dietary zinc supplementation and the performance and behaviour of caged laying hens

There is considerable behavioural evidence demonstrating stress reactions in birds. Behaviour of birds can affect their performance parameters. Also, nutritional factors may affect the behaviour of laying hens. Dietary deficiencies, such as minerals can increase feather-pecking behaviour and cannibalism. In the present study, we evaluate the effect of dietary zinc (Zn) on performance and behaviour of laying hens with four treatments (40, 70, 100, 130 mg Zn/kg of diet) with 96 Hy-Line W-36 leghorn hens for 10 weeks. The results showed that egg production for hens receiving 130 mg Zn/kg of diet was significantly higher than for those receiving 40 and 70 mg Zn/kg of diet (P < 0.05). Those hens receiving 130 mg Zn/kg of diet had lower feed consumption compared with those that had other treatments (P < 0.05). Dietary inclusion of Zn caused an improvement to feed conversion ratio (P < 0.05). There was a treatment x time interaction on feeding behaviour that hens received 130 mg Zn/kg of diet spent significantly less time at the feeder than the other treatments. Hens receiving 130 mg Zn/kg of diet spent significantly less time drinking than the hens that received 40 and 70 mg Zn/kg of diet. Also, those that received 130 mg Zn/kg of diet did more non-nutritive pecking and preening than the hens that received 40 and 70 mg Zn/kg of diet. High levels of Zn decreased the aggressive behaviour of hens compared with those that received 40 mg Zn/kg of diet (P < 0.05). It can be concluded that Zn can improve laying performance, and can decrease aggressive behaviour.