Control of Clostridium perfringens-induced necrotic enteritis in broilers by target-released butyric acid, fatty acids and essential oils.

The efficacy of target-released butyric acid, medium-chain fatty acids (C(6) to C(12) but mainly lauric acid) and essential oils (thymol, cinnamaldehyde, essential oil of eucalyptus) micro-encapsulated in a poly-sugar matrix to control necrotic enteritis was investigated. The minimal inhibitory concentrations of the different additives were determined in vitro, showing that lauric acid, thymol, and cinnamaldehyde are very effective in inhibiting the growth of Clostridium perfringens. The in vivo effects were studied in two trials in an experimental necrotic enteritis model in broiler chickens. In the first trial, four groups of chickens were fed a diet supplemented with butyric acid, with essential oils, with butyric acid in combination with medium-chain fatty acids, or with butyric acid in combination with medium-chain fatty acids and essential oils. In all groups except for the group receiving only butyric acid, a significant decrease in the number of birds with necrotic lesions was found compared with the infected, untreated control group. In the second trial the same products were tested but at a higher concentration. An additional group was fed a diet supplemented with only medium-chain fatty acids. In all groups except for that receiving butyric acid in combination with medium-chain fatty acids and essential oils, a significant decrease in the number of birds with necrotic lesions was found compared with the infected, untreated control group. These results suggest that butyric acid, medium-chain fatty acids and/or essential oils may contribute to the prevention of necrotic enteritis in broilers.

Effect of organic acids in drinking water during the last 2 weeks prior to slaughter on Salmonella shedding by slaughter pigs and contamination of carcasses.

In this study, we investigated the effect of adding organic acids to the drinking water of finishing pigs 2 weeks prior to slaughter on the shedding and prevalence rate of Salmonella at slaughter. Approximately 600 animals from four Belgian pig herds infected with Salmonella were included. At two herds, the study was conducted twice. Before the start of the study, overshoes were taken at the different herds. Two weeks prior to the expected slaughter date, the pigs were randomly divided into two groups (treatment and control group) each containing on average 50 animals within each herd. The treatment group received from this day onwards acidified drinking water (pH = 3.6-4.0), the control group received non-treated water (pH = 7.8-8.5). All other housing, feeding and management factors were identical in both groups. At the slaughterhouse, 10 pigs of each group (20 pigs for each group of study group 6) were randomly selected and sampled (blood, contents of ileum and rectum, mesenteric lymph nodes and carcass swabs). All samples were immediately transported to the laboratory and submitted to Salmonella isolation. Salmonella was isolated out of 11.9% (66/554) of the samples taken at the slaughterhouse, with the highest frequency found in the content of the ileum (18.7%), followed by 17.8% in the lymph nodes, 7.2% in the content of the rectum and 3.6% in the carcass swabs. The results did not reveal a significant difference between the treatment and control groups for the different slaughterhouse samples. The study documented that the investigated control strategy namely, the strategic application of organic acids during the last 2 weeks prior to slaughter was insufficient to decrease Salmonella shedding and contamination shortly before and during slaughter.

Variability in antimicrobial resistance among Salmonella enterica strains from fattening pigs and sows.

The aim of this study was to determine the prevalence of antibiotic resistance and different resistance patterns for Salmonella isolates collected from Belgian sows and fattening pigs at different ages and at slaughter. The most frequently isolated serotypes were S. Typhimurium (42.3%), S. Derby (25.1%), S. Goldcoast (7.3%), and S. Infantis (4.8%). All 901 isolates were submitted to antimicrobial susceptibility testing for 14 compounds using the disc agar diffusion test. The highest percentage of resistance was found to oxytetracycline (34.2%), streptomycin (32.5%), sulfamethizole (27.6%), and ampicillin (24.9%). Three of the isolates showed resistance to cephalosporins and none to second-generation fluoroquinolones. Multiresistance (resistance to > or =2 antimicrobials) was observed in 33.2% of the strains. Differences in resistance patterns were observed between and within serotypes as well as genotypes. A significant lower proportion (p < 0.01) of resistant strains was recovered in fecal samples from sows (23/56) than from fattening pigs during the weaning (30/30), growing (79/85), and finishing periods (45/52). The proportion of resistant strains recovered from fecal samples taken at the herd (154/167) was higher than in the samples collected at the slaughterhouse (75/140). When designing antimicrobial resistance surveillance programs for Salmonella in pigs, it is important to take multiple samples within each herd from both sows and fattening pigs at different time points.

Risk factors for the herd-level bacteriologic prevalence of Salmonella in Belgian slaughter pigs.

Herd-level risk factors for salmonellosis in pigs were investigated in a cross-sectional study on 62 Belgian farrow-to-finish pig herds belonging to one slaughterhouse cooperative. Data concerning housing and ventilation, management, hygiene, biosecurity, production parameters, feeding, disease control and transport to the slaughterhouse were collected during a herd visit by means of a questionnaire. The percentage of positive animals in a slaughterhouse delivery, as determined by qualitative Salmonella isolation in the mesenteric lymph nodes taken from 30 slaughter pigs, was the outcome variable. All samples were taken in 4 different slaughterhouses. Variables first were submitted to a univariable analysis using a logistic mixed regression model, with herd as random effect. Variables which were related to the Salmonella prevalence (P < 0.05) were analysed further in a multivariable model. The clustering of Salmonella infection within a pen also was studied in a generalised mixed model with pen as random effect. Salmonella isolates were identified by serotype. In 57 (92%) of the herds, at least one sample was found positive for Salmonella. The median percentage of positive Salmonella samples per delivery was 64% (range: 0-100%). In the multivariable model, only type of floor was related significantly to the prevalence: 100% (95% CI 88-100) for herds with <50% slatted floors to 54% (36-70) for herds with fully slatted floors. The results from the analysis should be interpreted with care because only 62 herds were included in the study. Clustering between pigs from the same pen could not be demonstrated (variance +/- S.D.: 0.11 +/- 0.16). S. typhimurium (30%) and S. derby (20%) were most common among the 23 different serotypes that were found.