GROUP SELECTION FOR ADAPTATION TO MULTIPLE-HEN CAGES - HUMORAL IMMUNERESPONSE

A selected line of White Leghorns, which has shown improved survivabil ity and reduced feather loss in large multiple-hen cages, was evaluate d for humoral immune response to SRBC under both stressed and unstress ed conditions. Three lines of chickens (selected, control, and commerc ial) were housed in either single- (1 hen) or multiple-hen cages (12 h ens, social competition) and subjected to a cold ambient temperature ( 0 C) at 33 wk of age and to two heating episodes (38 C) at 44 wk of ag e. Each hen was challenged intravenously with 1 mt of a 7% saline susp ension of SRBC at the time that cold exposure was initiated. Hens subj ected to high ambient temperatures had been exposed,previously to a co ld temperature, but were not challenged with SRBC until 16 to 18 h fol lowing the end of the second heating episode. Exposure to cold caused immunosuppression in single-caged hens, but hot in liens in colony cag es. Single- vs colony-caged hens of the control environment challenged with SRBC at 33 wk of age had similar primary hemagglutinin responses to SRBC. Hens subjected to heat experienced immunosuppression at 9 an d 12 d following challenge to SRBC when compared to the controls. Hens of multiple-bird cages challenged with antigen at 44 wk of age had a significantly lower hemagglutinin response to SRBC than those reared i n single-bird cages. The three lines of genetic stock had similar prim ary hemagglutinin responses to SRBC the interactions of genetic stock with cage size or environmental temperature were not significant. It w as concluded that genetically selecting hens for survival in multiple- hen cages did not affect their humoral immune response to SRBC.