270 Prenatal stress programming: Impact on dam and offspring immune phenotype and performance

Abstract Maternal stress during critical periods of fetal development is linked to the modified expression of several physiological processes. Despite attempts to minimize chronic stress and enhance sow well-being, some animals still experience stress, which can have short and long-term effects on future progeny. Therefore, we evaluated the impact of maternal stress on the immune phenotype and performance of pregnant gilts who had experienced pre- and post-natal stress and whether their offspring were affected. A total of 11 primiparous females (201.32 ± 17.18 kg at farrowing) clustered into treatment groups based on the treatment of their dams were used in this study. Their dams had been randomly allotted to receive either a placebo (CON) or Hydrocortisone Acetate capsules twice per day for 21 d during either mid (MID; d 51 to 72) or late (LATE; d 81 to 102) gestation. Prenatally stressed dams were sampled on gestational d 45, 60, 75, and 105 to determine descriptive and functional immune analysis. Productivity measures were assessed, including farrowing duration and the interval between piglets. Blood samples were taken from a subset of piglets born to these dams on d 7, 14, and 21 of lactation and then 24 h, 7, and 14 d post-wean. Data were analyzed using the Mixed procedure of SAS with repeated measures. Numbers of lymphocytes were elevated in gilts from LATE-treated dams compared with those from MID or CON dams for the entire study period (P < 0.05). All other descriptive immune measures, including neutrophil-to-lymphocyte ratio, were not different between groups during the gestational period. Mitogen-induced lymphocyte proliferation did not differ across treatments for prenatally stressed dams. No maternal treatment effects for any litter traits, farrowing duration, or interval between each piglet, but there was a tendency (P < 0.10) for piglets born to MID-stressed dams to be heavier than those born to CON dams. Total lymphocyte numbers were least in the progeny of MID-treated dams compared with piglets from LATE and CON dams for the entire lactation period. Over time, progeny from LATE-treated gilts had a more stimulated B-cell proliferation index during lactation (P < 0.05). Conversely, Concanavalin-A-induced lymphocyte proliferation tended to be least in offspring from MID-treated dams compared with CON. They also tended to have less percentage and numbers of lymphocytes than offspring from LATE and CON dams for the entire post-wean period. The offspring from MID-treated dams also had the greatest (P < 0.05) neutrophil-to-lymphocyte ratio for the entire period. While prenatal stress had minimal impact on the immune expression of the dam, its influence was evident in their progeny, particularly with MID. Results indicate that the programming effects may only be apparent in later generations. The study also suggests that mid-gestation is a more sensitive period for maternal stress in fetal development.