Submitted to: Journal of Animal Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 9/6/2001
Publication Date: N/A
Interpretive Summary: With increased public concern regarding the welfare and well-being of domestic livestock, there has been an increased effort by the scientific community to evaluate various methods and strategies to reduce stress in domestic animals. One means by which stress may be reduced in the neonatal pig is to minimize activation of the immune system. The objective of this study was to determine if supplementing the young pig's diet with spray-dried plasma would alter the stress response of the young pig to an endotoxic challenge. In this study, we found that when pigs were supplemented with spray-dried plasma for a period of 7 d following weaning, basal activation of the stress axis did not differ. However, following the endotoxic challenge, pigs supplemented with the spray-dried plasma had an increased stress response as compared to pigs fed a diet without the spray-dried plasma. These results are similar to our previous work which demonstrated that feeding spray-dried plasma causes an overactivation of the immune system to the endotoxin. Thus, this research demonstrates a strong association between the immune and stress responses and suggests that, by minimizing the immune response, one can also minimize the stress experienced by the neonatal pig. This study also highlights the positive impact nutritional supplements can have on the overall health and well-being of the young pig. Results from this study will be of particular interest to swine producers, feed companies, and scientists working in the area of swine nutrition, health, and well-being.
Technical Abstract: A study was conducted with 20 weaned barrows (14 d, 4.98 +/ 0.21 kg) to determine the effect of feeding spray-dried plasma (SDP) after weaning on the pig's stress response to a lipopolysaccharide (LPS) challenge. After weaning, pigs were fed a diet containing 0 or 7% SDP for 7 d. On d 6 postweaning, all pigs were nonsurgically fitted with a jugular catheter. On d 7 postweaning, the pigs were given i.p. injections of either saline o LPS (150 ug/kg BW) followed by serial blood collection every 15 min for a 3-h period. Following the 3-h blood collection, all pigs were killed and tissue collected for mRNA analysis. Pig weight on d 7 postweaning was not affected by dietary treatment (P>0.21). Pigs fed the diet with SDP had lower (P<0.05) levels of hypothalamic corticotropin-releasing hormone (CRH) mRNA, pituitary CRH receptor mRNA, and adrenal adrenocorticotropin-releasing hormone (ACTH) receptor mRNA. Dietary treatment did not affect pituitary proopiomelanocortin (POMC) mRNA. No effect of LPS treatment was observed in any of the mRNA levels examined. For both serum ACTH and cortisol, there was a significant diet by LPS treatment interaction (P<0.01) such that both the ACTH and cortisol responses to the LPS challenge were greater in the pigs fed the diet with SDP compared to pigs fed the diet without SDP. For pigs given the saline injection, diet did not affect basal serum cortisol concentration; however, basal serum ACTH concentration was lower in those pigs fed the diet with SDP (P<0.0001). These results demonstrate that pigs fed a diet with SDP have an increased activation of the pituitary-adrenal axis following an LPS challenge compared to pigs fed a diet without SDP.