Influence of acute feed deprivation or excess feed intake on immunocompetence of broiler chicks.

Immunocompetence was determined in chicks subjected to 24 h feed deprivation or excess intake by measuring 1) hemagglutinin titers in response to sheep red blood cell (SRBC) injections given either before or after dietary treatments, 2) delayed hypersensitivity to human gamma globulin (HGG), or 3) in vitro, phytohaemagglutinin-induced mitogenesis of spleen lymphocytes taken immediately or 24 h after dietary treatment. In Experiment 1, chicks were intubated six times during a 24-h period with an isolated soy protein-dextrose diet at either 100% (control) or 150% of ad libitum consumption. Following the period of excess intake, half of the chicks were prevented from making a compensatory decrease in intake by force-feeding (Hi-equal) and half were permitted to decrease their intake (Hi-adlib). All chicks not force-fed were sham-intubated. Imposing force-feeding (Hi-equal) before or after challenge with SRBC resulted in significantly (P less than .05) decreased hemagglutinin titers. Force-feeding (Hi-equal) 24 h prior to HGG injection significantly decreased delayed hypersensitivity. Hi-adlib chicks did not respond differently than controls. In Experiment 2, chicks were either fed ad libitum (control), fasted for 24 or 48 h and then fed ad libitum (Low24-adlib and Low48-adlib), or deprived of feed for 24 or 48 h and then restricted to normal intake (Low24-equal and Low48-equal). Imposing Low24-equal feeding prior to SRBC injection resulted in significantly greater (P less than .05) hemagglutinin titers after 7 days than observed in control chicks. No other differences were seen. These studies demonstrate that an acute period of uncompensated overconsumption or feed deprivation decreases and increases, respectively, selected aspects of the immune response.