GROUP SELECTION FOR ADAPTATION TO MULTIPLE-HEN CAGES - HEMATOLOGY ANDADRENAL-FUNCTION

A selected line of White Leghorns that has shown improved survivabilit y and productivity and reduced feather loss in multiple-hen cages was evaluated for hematological and adrenal responses under both stressed and unstressed conditions. It was hypothesized that hens selected for adaptation to multiple-bird cages would react less intensely to stress ors. Three Lines of chickens (selected, control, and commercial) were housed in either single-hen (1 hen) or multiple-hen cages (12 hens, so cial competition) at 16.7 or 17.1 wk of age. They were subsequently su bjected to cold exposure at 33 wk of age and heat exposure at 44 wk of age. Genetic stock as a main effect, and the interaction of genetic s tock with either a cold or heated environment or with cage size, had n o effect on plasma levels of cholesterol and corticosterone. At the ti me of transfer to laying cages, the selected line of pullets, as indic ated by a decrease in packed cell volume, appeared to adapt more quick ly to the new waterer system of multiple-hen cages than did the contro l and commercial lines. At 33 wk of age, the control and commercial li nes in multiple-hen cages experienced heterophilia and increased heter ophil to lymphocyte ratios, whereas the selected line did not, when co mpared with these same lines in single-hen cages. This leucocytic resp onse could be interpreted to mean that the selected line of chickens a dapted better to social competition than either the control or commerc ial lines; however, a similar leucocytic response was not observed at 18 or 44 wk of age. In conclusion, the physiological characterization of the selected line of Leghorns showed evidence of improved adaptatio n to multiple-hen cages when compared to the other stocks. In some cas es, the selected line responded less intensely to stress; however, tre nds were not always consistent.