title: Prevalence of Salmonella spp. on Canadian pig farms using liquid or dry-feeding.
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.
authors.affiliation: Department of Population Medicine, Ontario Veterinary College, University of Guelph, Guelph, Ontario, Canada N1G 2W1. afarzan@uoguelph.ca
authors.forename: Abdolvahab
authors.initials: A
authors.lastname: Farzan
authors.forename: Robert M
authors.initials: RM
authors.lastname: Friendship
authors.forename: Catherine E
authors.initials: CE
authors.lastname: Dewey
authors.forename: Keith
authors.initials: K
authors.lastname: Warriner
authors.forename: Cornelius
authors.initials: C
authors.lastname: Poppe
authors.forename: Kim
authors.initials: K
authors.lastname: Klotins
mesh_terms: D000821:Animal Feed; D000822:Animal Husbandry; D000818:Animals; D000900:Anti-Bacterial Agents / Q000494:pharmacology; D000907:Antibodies, Bacterial / Q000097:blood; D024881:Drug Resistance, Bacterial; D004797:Enzyme-Linked Immunosorbent Assay / Q000662:veterinary; D005243:Feces / Q000382:microbiology; D008826:Microbial Sensitivity Tests; D009864:Ontario / Q000453:epidemiology; D012307:Risk Factors; D012475:Salmonella / Q000187:drug effects / Q000276:immunology / Q000302:isolation & purification; D012481:Salmonella Infections, Animal / Q000097:blood / Q000453:epidemiology* / Q000382:microbiology*; D016036:Seroepidemiologic Studies; D011795:Surveys and Questionnaires; D013552:Swine; D013553:Swine Diseases / Q000097:blood / Q000453:epidemiology* / Q000382:microbiology*
chemical_list: D000900:Anti-Bacterial Agents; D000907:Antibodies, Bacterial