28 On-Farm Rapid Test to Assess Immunological Health of Young Pigs

Abstract

Abstract Immunological competence is important for young pig survivability. A rapid on-farm test of immunological status may be a tool to help with early identification of sick animals. A new immunological test uses gold nanoparticle technology (D2Dx) to detect changes in serum proteins, particularly IgG and was evaluated as a potential on-farm measure of immunological health of pigs born during a farm level Porcine Respiratory Reproductive Syndrome (PRRS) outbreak. Up to three piglets from each litter in 2 farrowing groups (28 days apart) were selected for serial blood sampling and monitoring of body weight. Group 1 (n = 13 sows) experienced the PRRS outbreak approximately 14 days before farrowing and Group 2 (n = 15) approximately 40 days before farrowing. Attempts were made to select one piglet from each of 3 general categories [small (< 1.0 kg), average (1.1 – 1.6 kg), heavy (>1.6 kg)] from each litter. Serum samples were collected at day 2 and 15 of age from each piglet and serum IgG concentration and D2Dx ratio were assessed. Serum immunocrit at day 2 was also completed. Daily animal care of piglets and sows followed standard barn protocols. No creep feed was provided, sows were fed ad libitum, and cross-fostering was limited. Stillborn rate and preweaning death loss was approximately 70% in Group 1 and 35% in Group 2. Birth weight was similar between Group 1 and 2 litters (1.4 ± 0.3 kg). However, body weight gain to day 15 was 1.7 ± 0.95 kg and 2.7 ± 1.1 kg for piglets from Group 1 and 2, respectively, which may be due to timing of the PRRS outbreak. The D2Dx ratio declined from day 2 to 15 (0.029 vs -0.002) in both groups and was significantly reduced in Group 2 pigs (P < 0.001). A lower ratio suggests a stronger type 2 immune response and has been associated with decreased overall immunity in cattle, humans, and rodents. The D2Dx ratio was negatively correlated (r = -0.58) with BW gain in Group 1 pigs and positively correlated (r = 0.36) with gain in Group 2 pigs. Both immunocrit (day 2) and IgG (d15) were greater in Group 1 pigs than Group 2 (P < 0.01). There was a no relationship between birth weight and day 2 serum immunocrit (R2 = 0.06) or day 2 D2Dx (R2 = 0.01). There was no relationship between serum IgG and D2Dx at d15. The PRRS disease activity impacts immunocrit and serum IgG measures in the neonatal pig. The D2Dx ratio was not strongly related to piglet immunological status under disease conditions; however, the stronger type 2 immune response may be reflective of positive changes in piglet immune function and the response to maternal PRRS antibodies in milk.