Influence of perches and footpad dermatitis on tonic immobility and heterophil to lymphocyte ratio of chickens

The purpose of the present study was to analyze the effect of perches and footpad dermatitis on stress and fear levels of chickens. In experiment 1 heterophil to lymphocyte ratio and tonic immobility duration were measured in 36-wk-old hens (36 birds) from 2 Spanish breeds of chickens (Black Menorca and Quail Castellana) housed in pens with or without perches from 20 wk of age. There was a significant difference in the heterophil to lymphocyte ratio between perch treatments (P < 0.05), the ratio of hens with perches being lower than that of hens without perches. Hens with perches had significant lymphophilia (P < 0.05). There was no significant difference for the duration of tonic immobility between hens with or without perches. Thus, hens with perches were less stressed than hens without perches, as indicated by the heterophil to lymphocyte ratio. Heterophil to lymphocyte ratio and heterophil number for Black Menorcas were significantly smaller (P < 0.001) than for Quail Castellanas, whereas lymphocyte number was greater in Black Menorcas. The Black Menorca hens had significantly (P < 0.01) shorter tonic immobility duration. In experiment 2 heterophil to lymphocyte ratio and tonic immobility duration were measured in 52-wk-old cocks (36 birds) of each of two different Spanish breeds of chickens (Black Barred Andaluza and Red Barred Vasca) housed in cages from 36 wk of age and showing or not showing footpad dermatitis. There was no significant effect of footpad dermatitis on the heterophil to lymphocyte ratio, its numerator, or its denominator, whereas there was significant effect on tonic immobility duration (P < 0.05) with tonic immobility of cocks with footpad dermatitis being longer than that of cocks without footpads. Thus, cocks with footpad dermatitis were more fearful than cocks without footpad dermatitis, as indicated by the tonic immobility duration. Heterophil to lymphocyte ratio and heterophil number were significantly smaller (P < 0.05) for Black Barred Andaluzas than for the Red Barred Vascas.