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

Prev Vet Med. 2006 Mar 16;73(4):241-54. doi: 10.1016/j.prevetmed.2005.09.003. Epub 2005 Sep 30.

Abstract

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.

MeSH terms

  • Animal Feed
  • Animal Husbandry
  • Animals
  • Anti-Bacterial Agents / pharmacology
  • Antibodies, Bacterial / blood
  • Drug Resistance, Bacterial
  • Enzyme-Linked Immunosorbent Assay / veterinary
  • Feces / microbiology
  • Microbial Sensitivity Tests
  • Ontario / epidemiology
  • Risk Factors
  • Salmonella / drug effects
  • Salmonella / immunology
  • Salmonella / isolation & purification
  • Salmonella Infections, Animal / blood
  • Salmonella Infections, Animal / epidemiology*
  • Salmonella Infections, Animal / microbiology*
  • Seroepidemiologic Studies
  • Surveys and Questionnaires
  • Swine
  • Swine Diseases / blood
  • Swine Diseases / epidemiology*
  • Swine Diseases / microbiology*

Substances

  • Anti-Bacterial Agents
  • Antibodies, Bacterial