Gutierrez Banuelos, Hector (2009-05). Use of novel compounds to reduce methane production and in pre-harvest strategies to decrease foodborne pathogens. Doctoral Dissertation.
Thesis
The first aim of this study (Chapter III), the effects of chlorate and nitroethane on foodborne pathogens and rumen fermentation were evaluated. The experimental chlorate product, reduced (P < 0.001) fecal, but not ruminal (P > 0.05) E. coli concentrations by 1000- and 10-fold by 24 and 48 h after chlorate feeding when compared to pre-treatment concentrations (> 5.7 log10 colony forming units/g). Nitroethane treatment decreased (P < 0.01) ruminal (8.46, 7.91 and 4.74 +- 0.78 umol/mL h-1) and fecal (3.90, 1.36 and 1.38 +- 0.50 umol/g h-1) methane-producing activity for treatments 0, 80 and 160 mg nitroethane/kg body weight per day, respectively. Whole animal methane emissions, expressed as L/d or as a proportion of gross energy intake (%GEI) were unaffected by nitroethane treatment (P > 0.05). The second aim of this study (Chapter IV) was conducted to examine the effects of nitroethane and monensin on ruminal fermentation and nitro-metabolizing bacterial populations in vitro. The addition of nitroethane decreased methane production (umol/mL) by at least 90%. The most probable number (MPN) of nitro-metabolizing bacterial populations was increased (P < 0.01) with the addition of nitroethane by at least 3 log10 cells/mL compared with monensin, monensin plus nitroethane or the control group. The final aim of this study (Chapter V) evaluated the effect of two sources of tannins, chestnut (CT) and mimosa (MT) on foodborne pathogens when applied as a hide-intervention and as a feed additive to feedlot cattle. Tannin spray application showed no effect of treatment or application-time (P > 0.05) on E. coli/total coliforms and total aerobes. Chestnut tannin decreased bacterial load of ruminal E. coli and total coliform by at least 0.4 log10 CFU/mL. However, fecal E. coli concentrations were increased with mimosa by 0.3 log10 CFU/g. Also, fecal total coliforms increased with the addition of chestnut or mimosa by at least 0.3 log10 CFU/g. Fecal Campylobacter concentrations (log10 CFU/g) increased with the addition of chestnut and mimosa by at least 0.4 log10 CFU/g.
