In three replicate trials, a total of 36 pigs that had been cannulated at the terminal ileum were used to determine the effects of a Saccharomyces cerevisiae culture in a phase feeding program (phase I was d 0 to 7 and phase II was d 8 to 21) on performance, ileal microflora, and short-chain fatty acids in weanling pigs. Pigs were cannulated at approximately 12 d of age, weaned at 17 d of age, and randomly assigned to one of three treatments: 1) a pelleted phase feeding program, 2) a similar program with the inclusion of a live S. cerevisiae culture (1 g/ kg), and 3) a nonpelleted feeding program otherwise similar to program 2. Ileal samples were collected at 17, 20, 24, 27, 31, 34, and 38 d of age, and samples were analyzed for total E. coli, streptococci, lactobacilli, yeast, short-chain fatty acids, pH, and dry matter. Performance data were also collected. At 41 d of age, pigs were killed and digesta were collected from various regions of the gastrointestinal tract. Total intake was less for pigs fed the control diet than for pigs fed the yeast diets, and overall gains tended to be greater for pigs fed diets including yeast. Treatment differences were not observed for ileal microflora or short-chain fatty acids in samples obtained from cannulas or from the various sites of the gastrointestinal tract. Inclusion of a live yeast culture in weanling pig diets affected intake and performance but did not alter tested intestinal microflora or net concentrations of fermentation products.

Sows and pigs from 10 commercial swine farms were sampled to determine patterns of resistance of fecal Escherichia coli to five commonly used antibiotics. Before testing, farms were categorized as high or low antibiotic use based on interviews with the respective producers. On each farm, fecal swabs were obtained from five sows at 7 d postpartum and from five pigs from each sow at 7, 35, and 63 d of age. A total of 6,296 E. coli isolates from 750 pig fecal samples and a total of 462 E. coli isolates from 50 sow fecal samples were tested against apramycin, carbadox, gentamicin, neomycin, and oxytetracycline using a standardized disk diffusion test. Percentage of resistant organisms was compared between pigs at the various stages of growth, between sows and their respective pigs, and between farms of high and low antibiotic use. Incidence of resistance was greater (P < .05) in pigs at 35 or 63 d of age compared with 7 d of age for most antibiotics, and patterns differed between high-use and low-use farms. Resistance differed (P < .05) among E. coli from pigs compared to their respective sows for apramycin and carbadox on low-use farms, whereas incidence of resistance on high-use farms differed (P < .05) between sows and pigs for apramycin and oxytetracycline. These data indicate that patterns of antibiotic resistance are dependent on age of pig and level of antibiotic use.

Antibiotic resistance of Escherichia coli from sows and pigs was determined to compare patterns between pigs of various ages and degrees of antibiotic use. Resistance patterns differed between farm types and pigs of differing ages, indicating that pig age and degree of antibiotic use affect resistance of fecal E. coli.

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