Effect of direct-fed microbials on rumen microbial fermentation.

Nonbacterial, direct-fed microbials added to ruminant diets generally consist of Aspergillus oryzae fermentation extract, or Saccharomyces cerevisiae cultures, or both. Results from in vivo research have been variable regarding effects of direct-fed microbials on ruminant feedstuff utilization and performance. Some research has shown increased weight gains, milk production, and total tract digestibility of feed components, but others have shown little influence of direct-fed microbials on these parameters. In vitro research with mixed ruminal microorganisms likewise has been inconsistent regarding the effects of direct-fed microbials. Several researchers observed that direct-fed microbials increased cellulolytic bacterial numbers in the rumen and stimulated the production of some fermentation end products. This suggests that direct-fed microbials may be providing growth factors for the ruminal microbes. However, other researchers have reported no effect of direct-fed microbials on in vitro fiber digestion. Recent research demonstrated that growth of the predominant ruminal bacterium Selenomonas ruminantium in lactate medium as well as lactate uptake by whole cells of Sel. ruminantium were markedly increased by an A. oryzae fermentation extract and an S. cerevisiae culture. In addition, both products increased the production of acetate, propionate, succinate, total VFA, and cell yield (grams of cells per mole of lactate). Therefore, it appears that these direct-fed microbials provide soluble factors that stimulate lactate utilization by Sel. ruminantium. Evidence is presented indicating that the malate content of the A. oryzae fermentation extract and S. cerevisiae culture may be involved in this stimulation.     

Prevalence of Escherichia coli O157 in cattle and swine in central Mexico

Escherichia coli O157:H7 is a foodborne pathogenic bacterium that can reside undetected in the gastrointestinal tract of cattle because colonization by this bacterium is asymptomatic. Recent research has indicated that swine can carry and transmit this pathogen as well. The development of more advanced and sensitive detection techniques has improved the limit of detection and increased sensitivity for this important pathogen. This study was undertaken to determine the prevalence of E. coli O157 in cattle and swine in Mexico with the more sensitive detection technique of immunomagnetic bead separation. Samples (n = 60 per farm) were taken from four cattle and four swine farms (n = 240 cattle samples, n = 240 swine samples) located throughout central Mexico in October 2001. The prevalence of E. coli O157 was found to be only 1.25% on cattle farms and 2.1% on swine farms. The prevalence in cattle in this study is lower than that reported in the United States and could be related to the lower reported prevalence of E. coli O157 in humans in Mexico. However, further research is needed to verify prevalence throughout other regions of Mexico, as well as prevalence during other seasons of the year.     

Effects of feed withdrawal and transport on cecal environment and Campylobacter concentrations in a swine surgical model

The objective of the present study was to evaluate how feed withdrawal and transportation influenced the cecal environment and cecal populations of Campylobacter in swine. Four miniature Yucatan gilts (8.8 kg), naturally infected with Campylobacter jejuni, were surgically implanted with cecal cannulas. The gilts were fasted for 48 h. Samples of cecal contents were collected for 7 days prior to and for 7 days after the fast, and mean values were determined for pH, volatile fatty acids (VFA), and CFU enumeration of C. jejuni. This was replicated three times. In another trial, gilts (full-fed) were transported in a livestock trailer for 4 h and cecal samples were collected before and after transport and analyzed for pH, VFA, and CFU. Following a 48-h fast, cecal pH increased (P < 0.05) by 1 unit; acetic and propionic acids decreased (P < 0.05) by 61% and 71%, respectively; and there was a twofold log10 increase (P < 0.05) in CFU/g cecal content of C. jejuni. Values of pH, VFA, and CFU of C. jejuni did not change in cecal samples from gilts following transportation. These data are important for food safety considerations because feed withdrawal, commonly associated with shipping and slaughter, can increase Campylobacter concentrations in the pig intestinal tract.     

Greenhouse gases in the Earth system: setting the agenda to 2030

What do we need to know about greenhouse gases? Over the next 20 years, how should scientists study the role of greenhouse gases in the Earth system and the changes that are taking place? These questions were addressed at a Royal Society scientific Discussion Meeting in London on 22-23 February 2010, with over 300 participants.     

Inhibition of in vitro Salmonella Typhimurium colonization in porcine cecal bacteria continuous-flow competitive exclusion culturest

Continuous-flow (CF) chemostate cultures were used as models to determine the potential usefulness of undefined porcine cecal bacteria as competitive exclusion (CE) cultures against colonization by Salmonella Typhimurium. One culture, pCF1, was derived from cecal bacteria of an animal maintained on antibiotic-free feed, while the other culture, pCF4, was derived from cecal bacteria of an animal maintained on feed containing chlortetracycline. The effectiveness against a chlortetracycline-resistant Salmonella Typhimurium was examined in CF cultures maintained in the absence (pCF1 and pCF4) and presence (cpCFl and cpCF4) of chlortetracycline. CF cultures were inoculated with each of 10(2), 10(4), and 10(6) Salmonella Typhimurium CFU/ml. Chemostat inocula of 10(2) Salmonella CFU/ml resulted in no Salmonella Typhimurium being detected at 2 and 3 days postinoculation in pCF1 and pCF4, respectively, and after 2 days in both cpCF1 and cpCF4. Inoculations of 10(4) Salmonella Typhimurium CFU/ml resulted in clearance from pCF1 and pCF4 within 4 days and within 3 days from cpCF1 and cpCF4. Following inoculation with 10(6) CFU/ml, no Salmonella Typhimurium were detected in all CF cultures by 6 days postinoculation. The results indicated that in vitro CF cultures of porcine cecal bacteria were able to inhibit the growth of Salmonella Typhimurium. The ability to limit Salmonella Typhimurium growth was not restricted by prior exposure of the cecal bacteria to the feed additive chlortetracycline. The present study demonstrates the potential application of CF cultures as models to aid in the identification of CE cultures against salmonellosis in pigs.     

Effect of sodium chlorate on Salmonella typhimurium concentrations in the weaned pig gut

Salmonella cause economic losses to the swine industry due to disease and compromised food safety. Since the gut is a major reservoir for Salmonella, strategies are sought to reduce their concentration in pigs immediately before processing. Respiratory nitrate reductase activity possessed by Salmonella also catalyzes the intracellular reduction of chlorate (an analog of nitrate) to chlorite, which is lethal to the microbe. Since most gastrointestinal anaerobes lack respiratory nitrate reductase, we conducted a study to determine if chlorate may selectively kill Salmonella within the pig gut. Weaned pigs orally infected with 8 x 10(7) CFU of a novobiocin- and nalidixic acid-resistant strain of Salmonella Typhimurium were treated 8 and 16 h later via oral gavage (10 ml) with 0 or 100 mM sodium chlorate. Pigs were euthanized at 8-h intervals after receiving the last treatment. Samples collected by necropsy were cultured qualitatively and quantitatively for Salmonella and for most probable numbers of total culturable anaerobes. A significant (P < 0.05) chlorate treatment effect was observed on cecal concentrations of Salmonella, with the largest reductions occurring 16 h after receiving the last chlorate treatment. An observed treatment by time after treatment interaction suggests the chlorate effect was concentration dependent. Chlorate treatment may provide a means to reduce foodborne pathogens immediately before harvest.     

Determination of important biochemical properties of honey to discriminate pure and adulterated honey with sucrose (Saccharum officinarum L.) syrup

The aims of the present study were to determine biochemical properties of honey samples and to discriminate pure and adulterated honey produced by the standard bee feeding method (control honey), the shaking method (pure blossom honey), and overfeeding (100 kg/colony syrup) with sucrose syrup (adulterated honey). The biochemical properties evaluated were moisture, ash, acidity, hydroxymethylfurfural (HMF), specific sugars (i.e. fructose, glucose, fructose–glucose, sucrose, and maltose), diastase activity, δ¹³C value (honey), δ¹³C value (protein), electrical conductivity, potassium, vitamin C, and proline. Fifteen honey samples were analyzed by discriminant analysis stepwise method. Proline, electrical conductivity and sucrose were found as discriminative characters of samples. Based on these three properties 100% of original group cases (samples) correctly classified in their real group. We found that the honey produced by feeding with 100 kg sucrose syrup per colony contained the sucrose as low as pure blossom honey. Therefore, the sugar (sucrose, fructose and glucose) content of honey cannot be used to distinguish between adulterated (sucrose syrup) and pure blossom honey.