Effect of efrotomycin in feed on the quantity, duration, and prevalence of shedding and antibacterial susceptibility of Salmonella typhimurium in experimentally infected swine.

The influence of efrotomycin administered at the rate of 16 mg/kg of feed in 10 Salmonella typhimurium-inoculated pigs was determined by comparing this group with a group of 10 pigs inoculated with S typhimurium that were given nonmedicated feed. Two control groups of 4 noninoculated pigs each, 1 group medicated with efrotomycin at 16 mg/kg of feed, the other nonmedicated, also were evaluated. An inoculum of 1.7 x 10(10) colony-forming-units/pig induced colonization of S typhimurium in all 20 pigs. Evaluation of the quantity of shedding did not reveal a clear or consistent treatment-related increase in S typhimurium counts; mean differences between the nonmedicated and medicated groups never exceeded 1 log unit. On the last day of the study (day 56 of the medication), 8 nonmedicated and 9 medicated pigs were determined to be infected with S typhimurium via enrichment procedures, so there was no difference in duration of shedding, and there were no significant differences in prevalence of shedding between the nonmedicated and medicated groups at any of the sampling times. Of 1,340 S typhimurium colonies isolated from the nonmedicated and medicated groups, 1,330 were susceptible to all 12 antibacterials tested, indicating no treatment-related effect on susceptibility. At necropsy, S typhimurium was not isolated from any liver or spleen specimens, and was isolated from only 2 of 20 lymph nodes. However, S typhimurium was isolated via enrichment from the cecal contents from all 20 pigs. There were no treatment-related differences in feed consumption, weight gain, or feed efficiency. Appreciable differences in the measurements were not found between the efrotomycin-medicated and nonmedicated pigs.

3-Acetyl-4''-isovaleryl tylosin for prevention of swine dysentery.

The 21 field isolates of Treponema hyodysenteriae which were tested were sensitive to 3-acetyl-4''-isovaleryl tylosin (AIV); the minimal inhibitory concentration was 0.25 to 16 micrograms/ml. 3-Acetyl-4''-isovaleryl tylosin administered prophylactically to pigs at concentrations of 5 to 100 mg/kg of feed and tylosin at 110 mg/kg of feed for 28 or 31 days prevented swine dysentery induced by tylosin-sensitive T hyodysenteriae strain SQ2; 15 nonmedicated, inoculated control pigs had bloody diarrhea, and 9 pigs died. In 2 additional trials, AIV administered prophylactically for 28 days at 55 or 110 mg/kg of feed prevented swine dysentery induced by tylosin-insensitive T hyodysenteriae strain B204. All of the inoculated principal pigs medicated with AIV at 55 or 110 mg/kg of feed or carbadox at 55 mg/kg of feed and the noninoculated sentinel pigs for each group had solid feces throughout the 56-day trial. In the nonmedicated, inoculated control groups, bloody diarrhea began at 4 to 5 days after inoculation was done, and 9 of 10 principal pigs and 6 of 9 sentinel pigs had dysentery; 2 pigs died. In the groups medicated with AIV at 27.5 or 5.5 mg/kg of feed, all 5 principal pigs and 3 or 4 sentinel pigs in each group had dysentery; 3 or 4 pigs in each group died. In the group medicated with tylosin at 110 mg/kg of feed, 7 of 10 principal pigs and all 9 sentinel pigs had dysentery; 1 pig died.(ABSTRACT TRUNCATED AT 250 WORDS)

Effects of diet, bacitracin, and body weight restrictions on the intestine of broiler chicks.

Six experiments were conducted to evaluate the effects of diet, bacitracin, and body weight restrictions on the intestine of the broiler chick. Bacitracin, at levels of 11 and 55 ppm, significantly increased body weight, significantly reduced small intestine weight, but had no significant effect on liver weight of chicks fed a soybean protein and sucrose-based diet. The greatest effects were observed in the ileum where weight, moisture, length per unit of body weight, and dry matter per unit of length were all significantly reduced. The least effects were observed in the duodenum where weight and length per unit of body weight were significantly reduced and dry matter per unit of length was significantly increased. Intestinal weight, as a percent of body weight, was not significantly affected when body weight was suppressed with a high level of nicarbazin added to a practical diet, but it was significantly reduced when bacitracin was added to the semipurified diet and chicks were restricted in food intake to 70% of controls. A level of 55 ppm of bacitracin added to the practical diet had no significant effect on body weight, intestinal weight, or liver weight. As discussed, the observed changes in the intestine, due to bacitracin, are probably indirect and most likely reflect the action of the antibiotic on the intestinal microflora.

Effects of diet and bacitracin on growth, feed efficiency, and populations of Clostridium perfringens in the intestine of broiler chicks.

Experiments were conducted to demonstrate the activity of bacitracin as a growth permittant for poultry and to further elucidate the mode of action of antimicrobial agents for that purpose. Supplementing a soybean protein and sucrose-based diet with 2.2, 11, and 55 ppm of bacitracin resulted in significant improvements in weight gain and feed efficiency of chicks fed the higher levels. In a second experiment, graded levels of bacitracin from 1.1 to 55 ppm were fed. A regression analysis of the index scores, the combined effects of both weight gain and feed efficiency, on the log of the significant dose levels of 5.5 to 27.5 ppm gave a linear response line with r = .996. Based on the equation, the ineffective level of the antibiotic was determined to be 4 ppm and the maximum effective level 31 ppm. Supplementing the soybean protein and sucrose-based diet with levels of 5.5, 16.5, and 55 ppm of bacitracin reduced the numbers of Clostridium perfringens organisms in ileal contents of chicks (all P less than .05). Chicks fed a level of 1.1 ppm, a level that did not give a growth response, had numbers of the organism present that were not significantly different from controls. Supplementing a soybean meal and corn-based diet with a level of 55 ppm of bacitracin did not significantly affect weight gain, feed efficiency, or numbers of C. perfringens in the ileum of chicks.(ABSTRACT TRUNCATED AT 250 WORDS)

In vitro and in vivo evaluations of the antibiotic efrotomycin.

Experiments were conducted to determine the potential of the antibiotic efrotomycin as a growth permittant for poultry and to further elucidate the mode of action of antimicrobial agents for that purpose. Efrotomycin as the semipurified antibiotic and as fermentation solids demonstrated excellent activity against Clostridium perfringens at .1 to .2 ppm based on suppression of gas production in an anaerobic tube test. Supplementing a soybean protein and sucrose-based diet with levels of 2.2, 11, and 55 ppm of the antibiotic, from the two sources each with two different purities, improved weight gain of chicks an average of 23% and improved feed efficiency an average of 13% at the higher levels (all P less than .01). Computed indexes for each antibiotic treatment, which represent the combined effects of both weight gain and feed efficiency, showed that a maximum response was generally obtained at the 11 ppm level and that the antibiotic as fermentation solids was slightly more active than the semipurified material. Supplementing the soybean protein and sucrose-based diet with levels of 1.1, 5.5, 16.5, and 55 ppm of efrotomycin reduced the numbers of C. perfringens organisms in ileal contents of chicks (all P less than .01). The effects were dose-related. Control chicks in this experiment averaged greater than 7.7 log10 of C. perfringens counts per gram of contents. The results of these experiments show that efrotomycin has excellent growth-permittant activity and the activity correlates with the antibacterial activity against C. perfringens.

Effect of the antibiotic thiopeptin on Clostridium perfringens and growth and feed efficiency of broiler chicks.

Experiments were conducted to determine the potential of the antibiotic thiopeptin as a growth permittant for poultry. Thiopeptin as the semipurified antibiotic and as fermentation solids demonstrated activity against Clostridium perfringens at .03 ppm based on suppression of gas production in an anaerobic tube test. Supplementing a soybean protein and sucrose-based diet with levels of 2.2, 11, and 55 ppm of thiopeptin from each of the two sources resulted in significant improvements in weight gain and feed efficiency of chicks fed the higher levels. Computed indexes for each antibiotic treatment showed that the antibiotic as fermentation solids was slightly more active than the semipurified material at the lower levels. Supplementing the soybean protein and sucrose-based diet with 1.1, 5.5, 16.5, and 55 ppm thiopeptin reduced significantly (P less than .01) the numbers of C. perfringens organisms in ileal contents of chicks. Chicks fed 5.5, 16.5, and 55 ppm thiopeptin also had significantly fewer C. perfringens organisms in the intestine than those fed 1.1 ppm. A discussion is presented of the biological responses of thiopeptin relative to the antibiotics efrotomycin and bacitracin.

Cephamycin C treatment of induced enterotoxigenic colibacillosis (scours) in calves and piglets.

Cephamycin C is a beta-lactam antibiotic that has broad gram-negative activity and is resistant to degradation by beta-lactamases and safe for use in animals. In colostrum-fed calves infected with Escherichia coli strain B44, cephamycin C administered by gavage at 31.3 to 1,000 mg per calf (0.75 to 24 mg/kg) twice a day for 6 days starting at 20 h post-inoculation eliminated the diarrhea and reduced the mortality from 90% in infected, nonmedicated calves to 14% in infected, medicated calves (P < 0.01). Comparable results were obtained with a shorter treatment regimen (30 mg of cephamycin C per calf [0.71 mg/kg] twice a day for 3 days). In colostrum-fed piglets infected with E. coli strain P155 and housed in cages, cephamycin C administered prophylactically by gavage at 12.5 mg per piglet (10.4 mg/kg) twice a day for 4 days completely prevented both diarrhea and mortality, whereas nonmedicated piglets had 100% diarrhea and all died. When eight doses of cephamycin C were given therapeutically starting at 6 h post-inoculation, mortality was reduced from 79 to 23% (P < 0.02), and diarrhea was eliminated in the surviving medicated piglets by 4 days post-inoculation. In infected suckling piglets, cephamycin C administered therapeutically by gavage at 12.5 mg per piglet twice a day for 3 days starting at 6 h post-inoculation, diarrhea and mortality were reduced (P < 0.05): infected, nonmedicated piglets had 87% diarrhea and 75% mortality, whereas infected, medicated piglets had 25% diarrhea and 31% mortality. All surviving medicated piglets had solid feces by 2 days post-inoculation. Thus, cephamycin C was highly effective in restoring the calves and piglets to good health by eliminating diarrhea and reducing mortality.