Influence of Dietary Antibiotics on Antibody Response to Specific Antigens

The influence of antibiotics in diets on antibody response to specific antigens has been measured in 144 early-weaned pigs. In the first experiment with pigs challenged at 27 days and antibody titer measured at 40 days the response was low and differences between treatments were not significant. In all remaining experiments in which pigs were 13 to 14 days older at time of challenge those pigs receiving zinc bacitracin, cycloserine and neomycin produced significantly greater antibody responses to bacterial antigens than did control pigs. Treatment differences occurred with antibiotics readily absorbed and with antibiotics minimally absorbed. The data suggest that the effect is initiated within the intestine. Weight gain was not significantly affected by treatment suggesting that antibody response differences occur previous to effects on weight gain.