An intervention study of the effect of implementing Salmonella-controlled feeding strategies in Salmonella-high prevalence herds

In this study we found a significant effect of implementing a salmonella-controlling feeding strategy for finishers, consisting of a pelleted feed where non-heat treated wheat or barley was added to the feed after pelleting. But not all trial herds reached Salmonella level I within the observation period, according to the Danish Salmonella Surveillance System, indicating the multi-factorial nature of Salmonella-infections. One issue that needs further research is the effect of the Salmonella level before entering the finishing period

The effect of feeding pellets, meal and heat treatment on the Salmonella-prevalence of finishing pigs

A previous trial (I) has shown that meal reduces the Salmonella prevalence and the degree of stomach changes as compared with pelleted feed. It was also found that coarsely ground feed tended to reduce the Salmonella problem compared with finely ground feed. The type of feed that reduced the Salmonella prevalence resulted in a substantially poorer feed conversion. There is a need to clarify what the feed industry can do to produce feed that reduces the risk of Salmonella problems and gastric changes and at the same time to clarify the effect on feed conversion. Thus, the object of the study was to clarify the effect of the pelleting process and the expansion of grain on the proportion of serological reagents against Salmonella and on gastric health and production result in finishing pigs

Salmonella reduction at the farm level

An important part of the Danish salmonella program is surveillance of all Danish pig herds with a yearly deliverance of more than 100 slaughter pigs. Herds categorized in infection level 2 or 3 are obliged to take effort to reduce the seroprevalence of slaughter pigs to an acceptable level. It has been shown, that it is possible to remove pigs from infected herds and raise them to the normal age of slaughter without detectable salmonella infection (Dahl and others, 1996). Based on these results, a model for salmonella reduction on herd level was established. The model consisted of a microbiological survey in the herd to locate infected parts of the herd. Based on the microbiological results a plan for reduction of salmonella was described for each individual farm. A typical plan consisted of hygienic measures combined with all in-all out measures on either pen-level or section level, in combination with an attempt to improve colonization resistance by using organic acids in water or feed

Strategies for elimination of S. typhimurium

Four different strategies were employed to try to eliminate Salmonella typhimurium from infected herds or pigs. Only strategic removal of pigs prior to entering infected sections of the herd was found to be beneficial. Strategies involving efforts to eliminate salmonella from infected pigs or herds by medication were found to be inefficient, and a vaccination strategy using a killed salmonella vaccine did not reduce subclinical infection

Salmonella-prevalences in Danish organic, free-range, conventional and breeding herds

The results from the Danish serological Salmonella surveillance on meat juice from slaughter pigs in the herd types: conventional herds, organic herds, free-range herds and breeder herds were compared. Seropositive samples were found in all herd types. The relative risk for a sample to be seropositive in free-range herds was 1.7 compared to conventional herds (p=O,OOOI) when confounder control for herd size was applied. An apparent increased risk in organic herds and reduced risk in breeder herds were not statistically significant. The analysis of results from organic herds was based on relatively few samples. Due to the expected increase in number of alternative production systems and difficulties in application of the full panel of recommendations for reduction of the Salmonella infection in these herds, future studies should focus on identification of specific Salmonella risk factors within alternative production systems and develop new tools based on this knowledge

Detection of S. enterica in different materials from the environment of pig herds

Salmonella contamination of pork carcasses as a result of subclinical salmonella infection in pig herds constitutes a menace to human health. Since 1993 there has been a national surveillance system in Denmark with the aim of monitoring and controlling salmonella infections in pig herds (Mousing et al., 1997). Application of the HACCP principles in control of salmonella infection at herd level depends on the possibility of characterizing the bacteriological status of the different sections of the herd in order to define the critical control points of the production. The objective of the present study was to characterize the microbiological status of the environment in pig herds with respect to different types of salmonella infection, and to evaluate the availability of material which is easy to collect and sensitive in the bacteriological examination

Bacteriological and serological characterisation of slaughter pigs from 25 serologically identified salmonella high risk herds

Danish finishing herds are routinely screened for antibodies to Salmonella in random samples of meat juice from slaughter pigs. The herds are categorized by the seroprevalence of samples from the preceding three months into three infection levels (1, 2 and 3). Herds are allocated to level 3 ( Salmonella high risk herds) at seroprevalences exceeding 33-50% depending on herd size (larger herds lower limit) (Mousing et al., in press)

Isolation of Salmonella enterica in seropositive classified finishing pig herds

The aim of this study was to assess the probability of detecting Salmonella from pen faecal samples in seropositive classified finishing pig herds. The study involved 77 herds from Denmark (20), the Netherlands (20), Greece (17) and Germany (20). The serological herd status was determined by the blood- sampling of 50 finishing pigs. Bacteriological sampling was performed by 20 pen faecal samples per herd. Over-all, 47 % of the blood samples had an OD% larger than 10 and 23 % larger than 40. Salmonella was isolated from 135 (9.3 %) pen faecal samples in 32 herds (42 %). Twenty-eight of these herds (87.5 %) had a within-herd seroprevalence larger than 50% at sample cut-off OD%\u3e10. A correlation coefficient of 0.62 was found between the proportion of culture positive- and seropositive samples in a herd at cut-off OD % \u3e 10 and of 0.58 at cut-off OD % \u3e 40. Due to the low sensitivity of culture methods, apparent ‘false positive’ serological results may well represent real infections not detected by bacteriological testing. In this study, there was an increasing probability of recovering Salmonella with increasing within-herd seroprevalence