Impact of Dietary Energy Source on the Responses of Pigs to an Acute Level of Antigen Exposure

and Implications Two trials were conducted to determine the response of pigs experiencing a low or high level of acute antigen exposure to three dietary energy regimens: a low-fat basal diet, basal diet plus 6% added choice white grease (low linoleic acid), and basal diet plus 6% added corn oil (high linoleic acid). All pigs were reared via a segregated early weaning scheme to minimize the pigs’ exposure to environmental antigens and thus level of immune system activation. Three littermate pigs in each of 24 litters were allotted at 21 days to one of the three dietary energy regimens for 37 days. Onehalf of the pigs in each trial were administered lipopolysaccharide (LPS), an acute stimulant of the immune system, on day 21 of the trial and again eight days later. LPS administration resulted in a short-term acute depression in pig performance in both trials. The magnitude and duration of the pigs’ response to LPS differed between trials and thus results are reported separately Prior to antigen (LPS) administration, dietary fat additions resulted in faster daily gains in trial 1 and greater efficiency of dietary energy (metabolizable energy, ME) utilization in trials 1 and 2. Responses to the two fat sources were similar in both trials. During the period of acute antigen exposure (day 0 to 4 post-LPS), daily weight gain and gain:ME ratios were similar among the three dietary regimens in both AE groups. Following partial antigen clearance from the body (day 4 to 8 post-LPS), dietary additions of either fat source again resulted in faster daily gains in trial 1 and improved gain:ME ratios in trial 2 in both AE groups. Based on these data, dietary additions of fat (both low and high in linoleic acid content) result in greater growth rates and efficiency of dietary ME utilization in pigs both prior to and following a period of acute antigen exposure.