Essential oils derived as by-products of the citrus industry have been investigated for antimicrobial properties against common foodborne bacteria and have been shown to possess bactericidal properties. The objective of the current research was to determine if feeding the citrus by-products D-limonene (DL) and citrus molasses (MOL) would reduce the concentration and prevalence of Salmonella in weanling pigs experimentally infected with Salmonella typhimurium. Twenty crossbred weanling pigs (average body weight [BW], 19.9 kg) were randomly assigned to one of four treatments: control (CONT), low-dose (LD) DL (1.5 ml/kg of BW per day), high-dose (HD) DL (3.0 ml/kg of BW per day), and MOL (0.05 kg/kg of BW per day). Treatments were administered in feed (twice daily) for 7 days, with one-half of the dose administered at each feeding. One day prior to initiation of the treatments, pigs were experimentally infected via oral gavage with 6 ml of tryptic soy broth containing 7.5 x 108 CFU/ml of Salmonella typhimurium. Fecal samples were collected twice daily (prior to administration of treatment) and cultured for quantitative and qualitative determination of the challenge strain of Salmonella. At the end of the study, pigs were euthanized and tissues from the stomach, ileum, cecum, spiral colon, and rectum, as well as luminal contents, were collected. In addition, the popliteal and ileocecal lymph nodes and liver, spleen, and tonsil tissue were collected for qualitative Salmonella culture.
No significant differences were observed when the data for each treatment was compared with those for control animals (CON versus LDDL, P = 0.30, and CON versus HDDL, P = 0.59). For the MOL treatment group, there was a tendency (P = 0.08) for fewer pigs to shed Salmonella following enrichment of fecal samples than for pigs receiving the CON treatment. Likewise, no treatment differences (P > 0.05) were observed for any of the tissue or luminal content samples collected. Salmonella was not cultured from the muscle-bound popliteal lymph node but was cultured from the mesenteric ileocecal lymph nodes.
While there were no effects in the current experiment, future research may examine the effect of a lower challenge dose and/or different administration (dose or duration) of the citrus by-products.
RL Farrow, TS Edrington, NA Krueger, KJ Genovese, TR Callaway, RC Anderson, DJ Nisbet. 2012. Lack of effect of feeding citrus by-products in reducing Salmonella in experimentally infected weanling pigs. Journal of Food Protection, 75(3):573-575. doi:10.4315/0362-028X.JFP-11-416.