Submitted to: Journal of Animal and Veterinary Advances
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: November 8, 2010
Publication Date: December 15, 2010
Citation: Collier, C.T., Carroll, J.A., Callaway, T.R., Arthington, J. 2010. Oral administration of citrus pulp reduces gastrointestinal recovery of orally dosed Escherichia coli F18 in weaned pigs. Journal of Animal and Veterinary Advances. 9(16):2140-2145. Interpretive Summary: A collaborative study was conducted involving scientists from the Livestock Issues Research Unit, the Food and Feed Safety Research Unit in College Station, and the University of Florida’s Range Cattle Research and Education Center in Ona, FL, to evaluate the effects of feeding citrus pulp to weaned pigs infected with Escherichia coli F18. Preliminary studies indicated potential growth advantages imparted by citrus pulp inclusion are due to antimicrobial characteristics; however, the possible regulatory role of citrus pulp on the immune response and resultant production improvement are ill-defined. Therefore, for this study, we evaluated the effects of citrus pulp on the immune and cortisol responses to Escherichia coli F18 inoculation and subsequent Escherichia coli F18 recovery in newly weaned pigs. Collectively, the results from this study demonstrate that the potentially therapeutic effects of citrus pulp are primarily the result of direct microbial modulation independent of an immune response. Therefore, supplementation of citrus pulp could potentially be used to enhance growth in weaned pigs by suppressing chronic and acute pathogenic challenges thus allowing more of the ingested nutrients to be diverted towards growth rather than the immune system. This information will be of interest to scientists working in the fields of immunity, nutritional alternatives to feeding antibiotics, and to swine producers in general.
Technical Abstract: The effects of citrus pulp (CTP) on the immune and cortisol responses to E. coli F18 inoculation and subsequent E. coli recovery were evaluated in newly weaned pigs (23.3 + 1.8 d of age). Barrows were assigned to 1 of 2 treatment groups; with (CTP; n = 15) and without (Control; n = 15) the in-feed inclusion of CTP (10% rate as fed) for 13 d. On d 13, all pigs were orally dosed with novobiocin (Nov) and nalidixic acid (Nal) resistant E. coli F18 (10 mL 7x108 CFU) at 0 h. Serial blood samples were collected via an indwelling jugular catheter inserted on d 12 at hourly intervals from 0 h to 8 h and then at 12 h, 24 h, 36 h, and 48 h. Differential blood cell populations were enumerated hourly from 0 to 8 h and at 12 h, 24 h, 36 h, and 48 h. Serum cortisol, interleukin-1 beta (IL-1), IL-6, tumor necrosis factor-alpha (TNF) and interferon-gamma (IFN) concentrations were determined via porcine-specific ELISAs at all time points. After 48 h, all pigs were euthanized and samples collected from ileal, cecal, and rectal contents for selective E. coli F18 standard plate counts on Nov- and Nal-treated media. White blood cells, lymphocytes, neutrophils, and macrophages were decreased (P < 0.05) from baseline equally in both treatments by 48 h. A more rapid cortisol suppression (P < 0.05) was observed in CTP-treated piglets after inoculation with a subsequent return to baseline in both treatments. The production of IL-1, IL-6, TNF, and IFN were unaffected by treatment or inoculation. However, the inclusion of CTP suppressed (P < 0.05) ileal and cecal E. coli F18 recovery compared to Controls and completely eliminated rectal recovery of the pathogen. These results demonstrate that the potentially therapeutic effects of CTP are the result of direct microbial modulation independent of an immune response. Therefore, supplementation of CTP could potentially be used to enhance growth in weaned pigs by suppressing chronic and acute pathogenic challenges, consequently preventing the diversion of energy towards maintaining innate and adaptive immune responses and liberating it for growth related processes.