Responses of dwarf and normal chickens to feed restriction, Eimeria tenella infection, and sheep red blood cell antigen.

Relationships among stress responses, habituation to feed restriction, resistance to Eimeria tenella, and antibody response to SRBC were studied in dwarf and normal White Plymouth Rocks. Transfer of chicks at 22 days of age from starter to developer batteries resulted in an increase within 24 h of heterophil:lymphocyte (H:L) ratios of chicks of both genotypes. Restriction of feed intake from ad libitum (AL) to 60% of ad libitum reduced body weight and increased size of the crop-esophagus. As measured by H:L ratios, the effect of adapting to the 60% feed restriction dissipated between 12 and 16 days after initiation. Release of 60% restricted chicks to 80% of ad libitum also elicited a stress response as measured by H:L. These effects were noted in both dwarf and normal chicks. Time required for chicks on restriction to consume their daily allotment was curvilinear with a plateau occurring at a smaller value for dwarf than for normal chicks. Neither feeding regimen nor genotype had an effect on antibody response to SRBC. Resistance to E. tenella was greater in normal than dwarf chicks and greater for restricted than ad libitum chicks.