The impact of phenotypic appearance on stress and immune responses in laying hens: Is it a group size dependent phenomena?.

MARIN R. H.; NAZAR, F. N.; LISTE M. G.; CAMPDERRICH I.; ESTEVEZ I.

Vitoria-Gasteiz

Congreso; 48º Congreso de la Sociedad Internacional de Etología Aplicada.; 2014

Alteration of birds? phenotypic appearance (PA) may lead to unwanted behaviours, potentially impairing poultry welfare, health and productivity. Likewise, group size (GS) may play an important role modulating the expression of adaptive behaviours and stress response. This study evaluated whether manipulation of the PA and GS in Hy-line Brown laying hens may affect stress and immune responses. At 1 day of age, 750 chicks were randomly assigned to 30 pens at GS either 10 or 40 (8 hens/m2). At arrival, PA of 0, 30, 50, 70 or 100% of the birds in each pen were artificially altered by black dying their heads back (Marked-M). Remaining birds were unchanged (Unmarked-UM). At 32 weeks, basal and acute stress adrenocortical response, heterophil/lymphocyte (H/L) ratio, lymphoproliferative response to phytohemagglutinin-p and primary antibody response against sheep red blood cells were measured in 6 birds/pen (3 M and 3 UM within the PA heterogeneous pens and 6 M or 6 UM from homogeneous pens). ANOVAs showed no differences among treatment combinations. In a second phase, birds in initially homogeneous pens (0 and 100%), were either M or UM sequentially to reach 30, 50 and 70% of the hens altered at 34, 38 and 44 weeks, respectively. Initially heterogeneous pens remained unaltered and were used as controls. Two weeks after last PA manipulation, mentioned variables were measured again. Both altered and non altered hens within altered pens showed increased (P