Submitted to: Poultry Science
Publication Type: Peer reviewed journal
Publication Acceptance Date: 1/10/2008
Publication Date: 4/15/2008
Citation: Nisbet, D.J., Edrington, T.S., McReynolds, J.L., Callaway, T.R., Byrd II, J.A. 2008. Influence of exogenous melatonin administration on Salmonella enteritidis colonization in molted layers. Poultry Science. 87:1083-1088. Interpretive Summary: Salmonella is a bacteria that can be found in chickens and is important because it can be transmitted from chickens to humans who eat eggs that are contaminated with Salmonella. Previous research conducted by our laboratory demonstrated that the hormone melatonin can reduce some types of harmful bacteria. The purpose of this study was to determine if different levels of melatonin would make chickens less likely to acquire Salmonella during molting. Results showed that chickens treated with a high level of melatonin and molting were more susceptible to Salmonella infection than chickens not receiving melatonin.
Technical Abstract: Two studies were conducted to evaluate the effects of exogenous melatonin on Salmonella enteritidis (SE) infection in experimentally-challenged laying hens subjected to a forced molt. Single Comb White Leghorn hens (W-36) over 50-wk-of-age were randomly placed in one of two rooms, allowed to acclimate for two weeks to 16-h light and 8-h dark regimen and provided ad libitum access to a non-medicated corn-soybean meal based mash layer diet and water. Birds in one room were molted (8 h light, 16 h dark; complete feed withdrawal), while birds in the second room served as non-molted controls (CONT). Within each room, birds were randomly assigned to melatonin treatment (MEL; 12 birds/treatment), dosed orally commencing the same day as feed withdrawal for 10 d: Experiment I - 0 or 5 mg melatonin; Experiment II – 0, 10 or 20 mg melatonin. Three days following feed withdrawal, chickens in all treatments were experimentally-infected with SE and after 10 d of feed withdrawal, all birds euthanized and tissue samples from the crop, ceca, liver, spleen and ovary collected for qualitative culture, as well as 0.25 g of cecal contents for quantitative determination of the challenge strain. In Exp. I, concentrations of SE in the cecal contents and the number of SE positive tissues from the crop, ceca, liver, spleen and ovary were higher (P < 0.0001) in the MOLT compared to the CONT treatments. No differences (P > 0.10) were observed in any of the parameters examined due to MEL treatment. For the second experiment, cecal concentrations of SE were generally higher in the MOLT compared to the CONT treatment. Additionally, within molted birds, cecal concentrations of SE were higher in the MEL treatment (P < 0.05) compared to no melatonin. Melatonin treatment in the molted birds increased (P < 0.05) the percentage of positive crops in the MOLT+20 MEL treatment (P < 0.05). Salmonella-positive cecal tissue was increased (P < 0.001) in MOLT compared to CONT birds and was also higher in MOLT+10 MEL and MOLT+20 MEL birds compared to the MOLT only treatment. The percentage of liver (P = 0.09) and ovary (P = 0.12) tissues SE positive tended to be higher in MOLT compared to CONT treatments. Results from the current research suggest that dosage with high levels of melatonin may exacerbate SE infection in layers subjected to forced molt.