Manipulation of the phenotypic appearance of individuals in groups of laying hens: effects on stress and immune related variables.

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

STRESS

TAYLOR & FRANCIS LTD

Lugar: Londres; Año: 2015 vol. 18 p. 710 - 717

1025-3890

This studyevaluated whether phenotypic appearance (PA) alteration during twodevelopmental phases in laying hens, reared in two different group sizes, affectsstress and immune responses. After hatch, 750 chicks were randomly assigned to30 pens at a group size of either 10 or 40 birds. Then, appearance of 0, 30, 50,70 or 100% of the chicks in each pen was altered by black-dying their headfeathers (Marked); remaining chicks were unmarked. At 32 weeks, basal andpost-acute stress plasma corticosterone concentration, leukocyte counts, phytohemagglutinin-p lymphoproliferative andprimary antibody responses were measured in 6 birds/pen. ANOVAs showed nodifferences among treatment combinations. In a second phase, birds withininitially homogeneous pens were sequentially either marked or had dye bleached toalter PA of 70% of hens in each flock (=group in a pen). Hens within initially heterogeneouspens remained unaltered as controls. The above variables were re-measured. Hensin phenotypically manipulated pens showed modified leukocyte counts compared to hens in control pens, indicating achronic stress reaction in all pen-mates (whether individual PA was altered ornot). Social isolation increased plasma corticosterone concentration. However,within groups of n=40, phenotypically unaltered hens had lower responses thantheir altered pen-mate counterparts, suggesting that remaining in a stable PA groupaids better coping with challenges. Although all hens in manipulated pensshowed modified leukocyte counts,their antibody and lymphoproliferative responses did not differ from controlssuggesting that all group-mates were able to immunologically cope with the challengespresented, within the time-frame evaluated.