Impact of Level of Antigen Exposure on Response of Pigs to Dietary Energy Sources

and Implications Two levels of chronic antigen exposure (moderate and high) were created by rearing pigs via a segregated-earlyweaning and a conventional rearing scheme, respectively. In each antigen exposure group, three littermate pigs in each of nine litters were fed one of three energy sources from 13 to 60 pounds body weight. Fifteen percent of the metabolizable energy (ME) content of the diets was provided by corn starch (CS), choice white grease (CWG), or corn oil (CO). Moderate AE pigs consumed more ME per day and grew faster than high AE pigs. The dietary inclusion of fat calories (CWG, CO) for starch calories resulted in greater daily body weight gains and gain:ME ratios in both moderate and high AE pigs. The magnitude of growth responses to the two fat calorie sources was similar in both AE groups. Based on these data, dietary fat calories support greater growth rate and efficiency of dietary ME utilization than starch calories in pigs experiencing either moderate or high levels of antigen exposure.