Thesis (M.Sc) -- Chulalongkorn University, 2010

Salmonellosis is widely known as major bood-born pathogen involved with poultry production. The objectives of this study were to determine the effect of (ORAs+ HMTBa) (formic acid, propionic acid and 2-Hydroxy-4-Methylthio Butanoic acid) on intestinal function and antioxidant enzyme activity of broilers challenged with nalidixic resistant Salmonella Enteritidis (SE). Five hundred eighty-eithty, one day old, male, Arbor acre broilers were divided into 4 treatment groups; CON group, SE group, SE+ORAs group and SE+(ORAs+ HMTBa) group, respectively. For SE+(ORAS) and SE+ (ORAs+HMTBa) groups were received organic acid in water at the first two weeks and the last week of experiment and were challenged with SE (108 cfu/ml) at days 1 and 7 as similar to SE group. In each replicate, SE was inoculated to half of the chicks. Corn-soybean meal basal feed and water were given ad libitum for 42 days. Qualitative and semi-quantitative SE examination, ileal digestibility and intestinal morphological study including liver and serum antioxidant enzyme activities were examined. The result demonstrated the horizontal transmission from inoculated chicks to non-inoculated chicks in liver-spleen pool and ileo-cecal content at day 14. Furthermore, the highest SE count was found in the ileo-cecal content of positive control group (SE) and no SE count was found in SE+ (ORAs+ HMTBa) group at day 21. IIeal digestibility of protein and fat in both ORA groups (groups 3 and 4) were higher than SE group at day 21 (P<0.05). At day 42, there was no significant change in digestibility among groups. It is discovered that villus height was higher and crypth depth was lower in SE+ (ORAs+HMTBa) group at days 14 and 21. There were no significant changes in antioxidant enzyme activity (GSH-px and GSH) and MDA concentration in all experiment groups at day 14, 21 and 42. In conclusion, the present study showed that combination of 2-Hydroxy-4-Methylthio Butanoic acid (HMTBa), formic acid and propionic acid were more efficient to prevent the horizontal transmission of SE in liver-spleen pool and ileo-cecal contents than conventional mixed organic acids. Furthermore, the ileal digestibility of protein and fat in chicks receiving ORAs+ HMTBa improved significant in the starter period of SE treatment. ORAs+HMTBa neither elicited the antioxidant effect nor reduced the pro-oxidant MDA in liver. The gut morphology was less influenced by effects of enhanced mixed organic acids.