Evaluation of alternatives to antibiotics using an Escherichia coli K88⁺ model of piglet diarrhea: effects on gut microbial ecology

¹ Department of Animal Science, University of Manitoba, Winnipeg, Manitoba R3T 2N2 Canada
² Cargill Animal Nutrition, Minneapolis, Minnesota

^* To whom correspondence should be addressed. E-mail: denis_krause{at}umanitoba.ca.

	Abstract

Enterotoxigenic E. coli is a major problem in the swine industry and results in scouring, increased mortality, and poor performance in the period immediately post-weaning. The traditional way to control this problem is to include sub-therapeutic antibiotics in the feed, but this is no longer acceptable to consumers, thus alternatives to antibiotics are needed. One of the supplements that have been effective in reducing scouring in the absence of antibiotics are animal blood products produced from the rendering process. This is also becoming a problem because of concerns regarding the transfer of transmissible spongiform encephalopathies to humans from animals. In this research we investigated the effects of spray dried porcine plasma (SDPP), a Bacillus subtilis direct fed microbial (DFM), a blend of organic acids, and sweeteners. A total of 108 pigs of approximately 17 d of age were assigned to 6 treatments, with 3 pigs per pen, in 2 blocks, with each block having 3 replicates. The 2 blocks were initiated approximately 2 mo apart, because sufficient pigs were not available that met our inclusion criteria in the first block. Diet 1 was a negative control containing no antibiotics (NC). Diet 2 was the positive control and included the same ingredient composition as NC except that antibiotics (110 mg/kg chlortetracycline, 110 mg/kg sulfamethazine, and 55 mg/kg penicillin) were added (PC). Diet 3 was equal to the NC, but with a Bacillus subtilis-probiotic (DFM). Diet 4 was the NC to which SDPP was added. Diet 5 was the NC plus a combination of SDPP and DFM (SDPP + DFM). Diet 6 was the NC plus a combination of supplements including SDPP and a blend of organic acids, DFM, and a sweetener (Blend). At 24 d of age, the pigs were experimentally infected with 6.3 x 10⁹ cfu·mL^-1 of E. coli K88. All pigs were euthanized 7 d after infection and tissues obtained for analysis. There were no significant differences among treatments for ADG, ADFI, G:F, plasma urea nitrogen, -acid glycoprotein, tumor necrosis factor-, intestinal ammonia, pH, and volatile fatty acids. However, the PC and DFM showed decreased (P < 0.05) scours at 24 h post-infection compared to NC, SDPP, and SDPP + DFM diets. Mortality in the NC that did not contain antibiotic was greater (P < 0.05) than in other treatments. Terminal restriction fragment length polymorphisms analysis (T-RFLP) of the 16S rDNA genes of digesta showed a higher incidence (P < 0.05) of Bacteroidetes in the PC and DFM diet than the NC. When SDPP and DFM were included in the diet the incidence of Bacteroidetes was also greater than in the NC (P < 0.05).

Key Words: antibiotics, Escherichia coli, microbial ecology, piglets, probiotic, T-RFLP