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United States Department of Agriculture

Agricultural Research Service

Title: Improving the Immune Status of Young Pigs

Author
item Carroll, Jeffery

Submitted to: International Symposium on Global and Regional Issues of Swine Production Proceedings
Publication Type: Proceedings
Publication Acceptance Date: July 23, 2004
Publication Date: July 23, 2004
Citation: Carroll, J.A. 2004. Improving the immune status of young pigs. Proceedings, International Symposium on Global and Regional Issues of Swine Production, July 23, 2004, Texas Tech University, Lubbock, Texas. p. 107-140.

Interpretive Summary: The issue concerning the use of subtherapeutic levels of antibiotics in animal production to enhance growth and performance (i.e., antibiotic growth promoter, AGP) and the perceived risk associated with the emergence of antibiotic-resistant bacterial strains has developed into a global issue. The use of AGP's in animal agriculture and the potential link to the development of antibiotic-resistant bacterial strains which could potentially affect human health has become a topic of discussion worldwide. Accordingly, in recent years, there has been an increase in research efforts directed towards evaluating various non-antibiotic compounds to prevent disease and infection, or to stimulate immune function in livestock. The primary immunologically-active compounds which have been investigated include antibodies, cytokines, and nutritional supplements such as spray-dried plasma (SDP) and fish oil. Research in our laboratory suggests that the enhanced performance of pigs consuming SDP is the result of the pigs being more immunologically naïve, thus allowing more nutrients to be diverted to growth rather than utilized for immune functions. Another nutritional strategy evaluated in our laboratory to modify the pig's response to an immune challenge is to supplement the diet with menhaden fish oil (MFO). Our research has demonstrated that dietary supplementation of MFO leads to significant alterations in the immunological and inflammatory response of the young pig to an immune challenge. Our overall results indicate that the inclusion of SDP or MFO in the weaned pig's diet for the first 10 to 14 days after being weaned from the sow results in significant alterations in the stress and immune responses following an immune challenge. Based on the indices measured in our studies, it would appear that both SDP and MFO supplementation offer immune protection to the young pig, thus allowing more nutrients to be diverted towards growth during this critical period of development. This information will be of interest to individuals working in the area of swine health and production, including scientists, extension personnel, and swine producers. Additionally, these results will be extremely useful to swine producers who are evaluating alternatives to the use of subtherapeutic levels of antibiotics in swine diets.

Technical Abstract: In recent years, there has been an increase in research efforts directed towards evaluating various non-antibiotic compounds to prevent disease and infection, or to stimulate immune function in livestock. One particular class of compounds, immune system modulators, has received considerable attention, and has been the subject of many scientific studies in the area of animal agriculture. The primary immunologically-active compounds which have been investigated include antibodies, cytokines, and nutritional supplements such as spray-dried plasma (SDP) and fish oil. Research in our laboratory suggests that the enhanced performance of pigs consuming SDP is the result of the pigs being more immunologically naive, thus allowing more nutrients to be diverted to growth rather than utilized for immune functions. In support of this theory are our results which demonstrate that pigs fed SDP exhibit greater immune stimulation when challenged with an endotoxin (i.e., lipopolysaccharide; LPS) from the cell wall of E. coli as demonstrated by increased serum cytokine responses associated with the acute phase immune response and a greater activation of the stress axis. We speculate that the increased immune and stress responses noted in pigs fed SDP is related to the lack of immunological priming. Feeding SDP is thought to have a protective effect in the pig, such that the immunoglobulins present in SDP are thought to bind to and prevent attachment of pathogens to the intestine, although other mechanisms may also be involved. Preventing pathogen attachment in the intestine would limit activation of the immune system, thus resulting in an animal which would not be fully immunocompetent, and would therefore have a greater immune response to an immune challenge such as LPS which bypassed the intestinal mucosa. Another strategy to modify an animal's response to an immunological challenge is to supplement the diet with menhaden fish oil (MFO). Previous work in our laboratory has demonstrated that dietary supplementation of MFO leads to significant alterations in the immunological and inflammatory response of the young pig to a LPS challenge. In these studies, growth performance was similar among the dietary groups prior to LPS challenge. We speculate that the environment in which the pigs were maintained was not sufficient to alter basal immune status, and therefore, growth should not have been affected. Due to the modulating effects of MFO on the immune system, it would be expected that if pigs were reared without antibiotics or copper sulfate in the diet or in an environment with a higher pathogen load, growth performance would have been different between the dietary groups. In our studies, pigs administered LPS evoked the expected rise in cortisol resulting from stimulation of the hypothalamic-pituitary-adrenal axis by pro-inflammatory cytokines. Pigs receiving diets containing MFO had lower serum cortisol during the challenge period as compared to pig diets containing corn oil. This would suggest that reduced levels of serum cortisol in pigs receiving MFO diets was reflective of reduced immune system activation most likely due to a decreased level of pro-inflammatory cytokines. Indeed, in these studies we observed an increase in TNF-alpha and IFN-gamma following LPS administration. Based on the indices measured in our studies, it would appear that SDP and MFO supplementation offer immunological protection to the young pig, thus allowing more nutrients to be diverted towards growth during this critical period of development. This information will be of interest to individuals working in the area of swine health and production, including scientists, extension personnel, and swine producers.

Last Modified: 7/24/2014
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