Maternal energy status during mid-gestation affects the immune response in the resultant beef offspring
Fetal or developmental programming relates the effects of maternal stressors on the developing fetus and potential consequences later in life. Specifically, beef cattle may experience decreased forage availability and quality during gestation, potentially altering nutrient availability and ultimately fetal development. Immune function has major economic implications in the beef industry; however, the understanding of maternal environment on development of the immune system in beef offspring is limited. Therefore, the objective of this study was to determine the effects of maternal energy status during mid-gestation on humoral immune response and tissue morphology of immunologically relevant tissues in beef offspring during the feedlot phase. Beef cows were allotted to one of two treatments: 1) Positive Energy Status (PES; n = 76)-fed to maintain BCS 5.0-5.5; or 2) Negative Energy Status (NES; n = 75)-fed to lose 1 BCS over the ensuing 91 day mid-gestation period (84 ± 11 days). Following treatment, cows were commingled and managed as a common group through weaning. Calves were weaned, shipped, and allotted into feedlot pens according to gender, dam energy status, and stratified by weight. A subsample (n=30) of calves were subcutaneously injected with 4 mg ovalbumin antigen at d 0 of antigen challenge and again on d 28 of antigen challenge, with blood collected every 7 days from d 0 through d 56 to measure antibody titers. An ELISA was used to determine serum antibody titers in response to the ovalbumin challenge. Additionally, a subsample of calves were harvested following the receiving (n=12) and finishing period (n=12) for histological examination with hematoxylin and eosin stain of lymph nodes, spleen tissue, and gut-associated lymphoid tissue. Ovalbumin data were analyzed as a repeated measures model using the PROC MIXED procedure of SAS (SAS Inc., Cary, N.C.). No morphological differences were observed in tissues. There were no differences (P>0.05) in gender main effects in response to a novel antigen. An anamnestic response was observed over time (P<0.05), which was expected following second exposure to the antigen. There was a difference (P< 0.05) between treatments over the sampling period with calves from PES cows having a greater antibody titer of 13.44 compared to calves from NES cows with an antibody titer of 12.38. These results suggest cows in a NES during mid-gestation produce calves with a decreased ability to produce antibodies to a novel antigen and thus a decreased humoral immune response.
Keywords: cattle, fetal programming, immunology