The effects of supplementation of broiler diets with organic acids on live performance and microbiological parameters were evaluated in a series of experiments. In three trials lactic acid (LA) (0.25 to 2.00%) or fumaric acid (FA) (0.5 to 2.00%), and in two trials a formic/propionic acid blend (FP) (.125 to 1.00%) or citric acid (CA) (0.25 to 2.00%) was continually fed to broilers that were inoculated via the drinking water with 108 to 109 CFU/ml nalidixic acid–resistant Salmonella typhimurium (NAL-SAL) on days 2, 7, and 14. Cecal pH, weight and percentage (on a live-weight basis) were measured at 41 days of age. Performance variables were measured at 21 and 42 days. At 42 days birds were processed and the ceca and prechill carcasses were evaluated for incidence and levels of NAL-SAL. LA, FA, and CA had no adverse effects on live bird performance. The FP blend gave inconsistent results on body weight and feed consumption; the blend did not alter feed conversion or mortality. Neither LA nor FA affected cecal pH; however, the pH was altered when the FP blend or CA was fed. None of the acids affected cecal weight or percentage. None of the acids consistently reduced levels of NAL-SAL in the ceca or on the prechill carcasses. The results from this study and numerous others suggest that feeding organic acids to broilers is not a reliable means of controlling cecal colonization or carcass contamination by Salmonella. The results also suggest that reductions in cecal colonization by pathogens such as Salmonella do not necessarily result in processed carcasses that are contaminated to a lesser degree.

Two similar trials were conducted to evaluate the accuracy of the whole carcass rinse technique in combination with a most probable number (MPN) procedure for estimating the number of salmonellae on postchill broilers. Birds were reared in litter-floored pens and inoculated with Salmonella typhimurium (10(8) cfu/mL) on Days 2, 7, and 14. In each of the two trials six carcasses were consecutively rinsed four times. Each carcass was rinsed with 100 mL of sterile water in sterile plastic bags using an automated shaking device. Salmonellae were enumerated using a three-tube MPN procedure in selenite cystine broth. There were no statistical differences in log10 MPN salmonellae per milliliter of recovered rinse fluid due to trial or consecutive rinse. In several cases salmonellae were not recovered in the initial rinse but were recovered from consecutive rinses of the same carcass. A large amount of variation in MPN levels of salmonellae among individual carcasses occurred within each consecutive rinse. The data suggested that only a percentage of the total salmonellae present on a postchill carcass were recovered with each consecutive rinse, and the organisms were firmly attached prior to processing.