Effects of Physical Properties of Feed on Microbial Ecology and Survival of Salmonella enterica Serovar Typhimurium in the Pig Gastrointestinal Tract

Abstract

A two-by-two factorial experiment with pigs was conducted to study the effect of feed grinding (fine and coarse) and feed processing (pelleted and nonpelleted) on physicochemical properties, microbial populations, and survival of Salmonella enterica serovar Typhimurium DT12 in the gastrointestinal tracts of pigs. Results demonstrated a strong effect of diet on parameters measured in the stomachs of the pigs, whereas the effect was less in the other parts of the gastrointestinal tract. Pigs fed the coarse nonpelleted (C-NP) diet showed more solid gastric content with higher dry matter content than pigs fed the fine nonpelleted (F-NP), coarse pelleted (C-P), or fine pelleted (F-P) diet. Pigs fed the C-NP diet also showed significantly increased number of anaerobic bacteria (P < 0.05), increased concentrations of organic acids, and reduced pH in the stomach. In addition, pigs fed the C-NP diet showed increased in vitro death rate of S. enterica serovar Typhimurium DT12 in content from the stomach (P < 0.001). Pigs fed the C-NP diet had a significantly higher concentration of undissociated lactic acid in gastric content than pigs fed the other diets (P < 0.001). A strong correlation between the concentration of undissociated lactic acid and the death rate of S. enterica serovar Typhimurium DT12 was found. In the distal small intestine, cecum, and midcolon, significantly lower numbers of coliform bacteria were observed in pigs fed the coarse diets than in pigs fed the fine diets (P < 0.01). Pigs fed the C-NP diet showed the lowest number of coliform bacteria in these segments of the gastrointestinal tract. Pigs fed the coarse diets showed increased concentration of butyric acid in the cecum (P < 0.05) and colon (P < 0.10) compared with pigs fed the fine diets. It was concluded that feeding a coarsely ground meal feed to pigs changes the physicochemical and microbial properties of content in the stomach, which decreases the survival of Salmonella during passage through the stomach. In this way the stomach acts as a barrier preventing harmful bacteria from entering and proliferating in the lower part of the gastrointestinal tract.Human food-borne disease outbreaks are a public health concern and have economic importance to the food-producing industry. Subclinical Salmonella enterica infections in pig herds are recognized as an important source of human salmonellosis in Denmark (29). A Danish Salmonella surveillance and control program in pig herds and slaughterhouses has been applied nationally since 1995, and the goal is to reduce the Salmonella prevalence in pork meat to 0.5% (23). In year 2002, the incidence of Salmonella-positive carcass samples in Danish slaughterhouses was 1.4% and the corresponding Salmonella prevalence at herd level monitored by serological testing was 3.2% (1).There is a growing awareness that it is only possible to reduce the prevalence of Salmonella in pork, and consequently the number of infections in people consuming pork and pork products, through an integration and cooperation of all sta...

The effect of high and low dietary crude protein and inulin supplementation on nutrient digestibility, nitrogen excretion, intestinal microflora and manure ammonia emissions from finisher pigs

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