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Journal of Food Protection Sep 2023Feedlot cattle commonly shed the foodborne pathogen Escherichia coli O157:H7 in their feces. Megasphaera elsdenii (ME), a lactic acid-utilizing bacterium, is commonly...
Feedlot cattle commonly shed the foodborne pathogen Escherichia coli O157:H7 in their feces. Megasphaera elsdenii (ME), a lactic acid-utilizing bacterium, is commonly administered to cattle to avoid lactate accumulation in the rumen and to control ruminal acidosis. The impact of administering ME on foodborne pathogen prevalence, specifically E. coli O157:H7, has not been explored. The purpose of this study was to quantify E. coli O157:H7 prevalence in finishing cattle administered ME. Cattle (n = 448) were assigned to treatments in a randomized complete block design with repeated measurements over two sampling periods. Treatments were arranged as a 2 × 2 factorial containing: ruminally protected lysine (RPL; included for a complementary study) fed at 0% or 0.45% of diet dry matter; with or without ME. Freeze-dried ME was administered as an oral drench (1 × 10 CFU/steer on day one) and then top dressed onto basal diets (1 × 10 CFU/steer) daily thereafter. Rectoanal mucosal swabs (RAMS) were obtained from animals before harvest to determine the E. coli O157:H7 prevalence. The inclusion of RPL (P = 0.2136) and ME (P = 0.5012) did not impact E. coli O157:H7 prevalence, and RPL was not included in any significant interactions (P > 0.05). A significant interaction was observed between ME and sampling period (P = 0.0323), indicating that the effect of ME on E. coli O157:H7 prevalence varied over the sampling period. A diet containing ME reduced the odds of E. coli O157:H7 prevalence by 50% during sampling period 1 (8.0% and 14.7% for cattle with and without ME, respectively) and increased the odds by 23% during sampling period 2 (10.8% and 8.9% for cattle with and without ME, respectively). Administering ME in cattle diets did not impact E. coli O157:H7 in feedlot cattle. This is the first study to investigate the use of ME as a preharvest food safety intervention in cattle, and additional research is necessary to determine the efficacy.
Topics: Animals; Cattle; Male; Animal Feed; Cattle Diseases; Colony Count, Microbial; Escherichia coli Infections; Escherichia coli O157; Feces; Megasphaera elsdenii; Prevalence; Probiotics; Sheep
PubMed: 37479183
DOI: 10.1016/j.jfp.2023.100133 -
Microbial Cell Factories Jul 2023Escherichia coli is a useful platform for producing valuable materials through the implementation of synthetic gene(s) derived from other organisms. The production of...
Escherichia coli is a useful platform for producing valuable materials through the implementation of synthetic gene(s) derived from other organisms. The production of lactate (LA)-based polyester poly[LA-co-3-hydroxybutyrate (3HB)] was carried out in E. coli using a set of five other species-derived genes: Pseudomonas sp. 61-3-derived phaC1STQK (for polymerization), Cupriavidus necator-derived phaAB (for 3HB-CoA generation), and Megasphaera elsdenii-derived pct (for LA-CoA generation) cloned into pTV118NpctphaC1p(ST/QK)AB. Here, we aimed to optimize the expression level and timing of these genes to improve the production of P(LA-co-3HB) and to manipulate the LA fraction by replacing the promoters with various promoters in E. coli. Evaluation of the effects of 21 promoter replacement plasmids revealed that the phaC1STQK-AB operon is critical for the stationary phase for P(LA-co-3HB) production. Interestingly, the effects of the promoters depended on the composition of the medium. In glucose-supplemented LB medium, the dps promoter replacement plasmid resulted in the greatest effect, increasing the accumulation to 8.8 g/L and an LA fraction of 14.1 mol% of P(LA-co-3HB), compared to 2.7 g/L and 8.1 mol% with the original plasmid. In xylose-supplemented LB medium, the yliH promoter replacement plasmid resulted in the greatest effect, with production of 5.6 g/L and an LA fraction of 40.2 mol% compared to 3.6 g/L and 22.6 mol% with the original plasmid. These results suggest that the selection of an appropriate promoter for expression of the phaC1STQK-AB operon could improve the production and LA fraction of P(LA-co-3HB). Here, we propose that the selection of cell-growth phase-dependent promoters is a versatile biotechnological strategy for effective intracellular production of polymeric materials such as P(LA-co-3HB), in combination with the selection of sugar-based carbon sources.
Topics: Lactic Acid; Escherichia coli; Polyesters; Hydroxybutyrates
PubMed: 37468909
DOI: 10.1186/s12934-023-02143-w -
Veterinary Medicine and Science Sep 2023The objective of the experiment was to investigate the effect of a mixture of direct-fed microbial (DFM) on feed intake, nutrient digestibility, milk yield and...
BACKGROUND
The objective of the experiment was to investigate the effect of a mixture of direct-fed microbial (DFM) on feed intake, nutrient digestibility, milk yield and composition, milk fatty acid and blood parameter in crossbred mid-lactating cows.
METHODS
Twenty-four crossbred Holstein cows (body weight = 650±15 kg; days in milk = 100±20; daily milk yield = 25±3 kg) were used in a completely randomized design with three treatments: (1) CON, without DFM; (2) LS, inoculation with Lactobacillus fermentum (4.5 × 10 CFU/day) plus Saccharomyces cerevisiae (1.4×10 CFU/day); and (3) LSM, inoculation with LS plus Megasphaera elsdenii (4.5 × 10 CFU/day). All animals received the same ration with 45.7% forage and 54.3% concentrate.
RESULTS
Results showed that the highest feed intake was observed in treatments LS and LSM (p = 0.02). Compared with the CON, milk production, 4% fat-corrected milk, energy-corrected milk, fat (kg/day), protein (kg/day) and lactose (kg/day), FE and percent of fat were increased (p<0.05) by LSM, but unaffected by LS. Also, compared with the CON, both LS and LSM increased antioxidant activity (p<0.05). The concentration of C18:2c n-6 increased significantly in treatment LSM compared with the CON (p = 0.003). The concentration of C20:0 increased significantly in treatment LS compared with the CON (p = 0.004). The highest concentrations of insulin, glucose, triglyceride and cholesterol were observed by LSM (p<0.05). Compared with the CON, both LS and LSM increased blood monocyte, neutrophil, eosinophil and basophil (p<0.05), and blood lymphocyte was increased (p = 0.02) only by LSM.
CONCLUSIONS
The results of the research showed that the use of DFMs had no effect on the digestibility, microbial load and the major part of fatty acids in milk. However, it improved feed intake, milk yield and antioxidant activity of milk and also increased the milk concentration of C18:2 n-6.
Topics: Female; Cattle; Animals; Milk; Fatty Acids; Lactation; Antioxidants; Diet; Digestion; Animal Feed; Dietary Supplements
PubMed: 37417715
DOI: 10.1002/vms3.1180