ETHOLOGICAL STUDY OF FREE-RANGE HENS WITH ZINC AND VITAMIN C SUPPLEMENTED DIET
Vasko Gerzilov, Lilyan Sotirov, Nadya Bozakova
Abstract: The study was designed to examine the effects of a dietary supplementation with zinc (35 mg/kg) and vitamin C (250 mg/kg) on the behaviour and plasma corticosterone in New Hampshire NG-line hens reared under free range conditions (sleeping pens and outdoor walking yards) during cold (7 oC), thermoneutral and hot (31oC) subperiods.
Hens’ behaviour was recorded by video cameras. Blood plasma corticosterone was assayed by ELISA.
In all birds, both low and high ambient temperatures, combined with high light intensity, induced a significant increase in plasma corticosterone compared to the thermoneutral period (P<0.01). During those periods hens were more aggressive which indicated poorer welfare. Hens supplemented with either zinc or zinc + vitamin C had lower plasma corticosterone than controls. Dietary zinc, either alone or co-administered with vitamin C, reduced plasma corticosterone and increased the number of egg-laying, dust bathing and preening birds during the cold and hot periods. The aggressive behaviour was reduced (P<0.01) indicating a higher welfare level.
The group supplemented with zinc + vitamin C showed more intensive preening and resting, as well as less aggression and movement than the zinc-supplemented group (P<0.05), suggesting a synergistic action of both supplements towards alleviating stress and therefore, a possibility for improving hen welfare.
Hens’ behaviour was recorded by video cameras. Blood plasma corticosterone was assayed by ELISA.
In all birds, both low and high ambient temperatures, combined with high light intensity, induced a significant increase in plasma corticosterone compared to the thermoneutral period (P<0.01). During those periods hens were more aggressive which indicated poorer welfare. Hens supplemented with either zinc or zinc + vitamin C had lower plasma corticosterone than controls. Dietary zinc, either alone or co-administered with vitamin C, reduced plasma corticosterone and increased the number of egg-laying, dust bathing and preening birds during the cold and hot periods. The aggressive behaviour was reduced (P<0.01) indicating a higher welfare level.
The group supplemented with zinc + vitamin C showed more intensive preening and resting, as well as less aggression and movement than the zinc-supplemented group (P<0.05), suggesting a synergistic action of both supplements towards alleviating stress and therefore, a possibility for improving hen welfare.
Keywords: behaviour; corticosterone; poultry welfare; stress; zinc and vitamin C
Date published: 2017-04-28
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