Prevalence of Salmonella spp. on Canadian pig farms using liquid or dry-feeding

• Published in: Preventive veterinary medicine 2006-03, Vol.73 (4), p.241-254
• Main Authors: Farzan, Abdolvahab, Friendship, Robert M., Dewey, Catherine E., Warriner, Keith, Poppe, Cornelius, Klotins, Kim
• Format: Article
• Language: English
• Subjects: absorbance; Animal Feed; Animal Husbandry; animal pathogenic bacteria; Animals; Anti-Bacterial Agents - pharmacology; antibiotic resistance; antibodies; Antibodies, Bacterial - blood; antimicrobial agents; blood chemistry; continuous flow husbandry; disease prevalence; Drug Resistance, Bacterial; ELISA; Enzyme-Linked Immunosorbent Assay - veterinary; feces; Feces - microbiology; feeds; food animals; food contamination; food pathogens; Liquid-feeding; liquids; medicated feeds; Microbial Sensitivity Tests; on-farm food safety; Ontario - epidemiology; Optical density; pathogen shedding; Pig; pig farms; Risk Factors; Salmonella; Salmonella - drug effects; Salmonella - immunology; Salmonella - isolation & purification; Salmonella Infections, Animal - blood; Salmonella Infections, Animal - epidemiology; Salmonella Infections, Animal - microbiology; salmonellosis; Seroepidemiologic Studies; seroprevalence; Shedding; Surveys and Questionnaires; Swine; Swine Diseases - blood; Swine Diseases - epidemiology; Swine Diseases - microbiology; swine feeding
• ISSN: 0167-5877; 1873-1716
• DOI: 10.1016/j.prevetmed.2005.09.003

The objective of this study was to determine whether the shedding and antibody titre to Salmonella was lower for pig herds provided liquid-feed compared to those on traditional dry rations. Twenty liquid-feeding farms and 61 dry-feeding farms were selected. The amount of antibodies to Salmonella in sera from 15 finisher pigs on each of 80 Ontario swine farms was analyzed by means of enzyme-linked immunosorbent assay (ELISA). In addition, the presence of Salmonella on the 20 liquid-feeding farms and 21 of the dry-feeding farms was assessed by culture of 15 fecal samples taken directly from finisher pigs and five pooled pen-fecal samples at each farm. A cut-off of OD% 10 was used. The Salmonella sero-prevalence differed between the two groups of farms. At least one pig tested sero-positive on 98% of the dry-feeding farms and 84% of the liquid-feeding farms ( P < 0.05). A multi-variable mixed linear regression model with the farm as a random variable and farm factors as the fixed effects was fitted. Crude optical density (OD) of the individual pig was considered as the continuous dependent variable. Dry-feeding and antimicrobial daily usage was associated with crude OD ( P < 0.05). In addition, crude OD increased with increasing herd size ( P < 0.05). Salmonella was isolated from 25 out of 420 fecal samples (6%) from dry-feeding farms compared to three out of 400 samples (0.8%) from liquid-feeding farms. Eight of the dry-feeding farms (38%) tested positive compared to only three of the liquid-feeding farms (15%). Salmonella was also recovered from the pen environment on five dry-feeding farms but were not isolated from the facilities using liquid-feeding. Salmonella Typhimurium was isolated from four farms in the dry-feed group and on one farm with liquid-feeding. The one S. Typhimurium isolate from the liquid-feeding farm exhibited no antimicrobial resistance, but those from dry-feeding farms were resistant to four or more antimicrobial agents. The results of the logistic regression, with farm as a random effect showed that dry-feeding [OR = 2.7 (1.1–15.1)] and continuous flow system [OR = 2.3 (1.2–12.7)] increased risk of finding Salmonella in the individual pig. These findings indicate that liquid-feeding and all-in all-out management of the grower–finisher barns can reduce the Salmonella prevalence.