Assessment of Potential Anti-Methanogenic and Antimicrobial Activity of Ethyl Nitroacetate, α-Lipoic Acid, Taurine and L-Cysteinesulfinic Acid In Vitro

Livestock producers need new technologies to maintain the optimal health and well-being of their animals while minimizing the risks of propagating and disseminating pathogenic and antimicrobial-resistant bacteria to humans or other animals. Where possible, these interventions should contribute to the efficiency and profitability of animal production to avoid passing costs on to consumers. In this study, we examined the potential of nitroethane, 3-nitro-1-propionate, ethyl nitroacetate, taurine and L-cysteinesulfinic acid to modulate rumen methane production, a digestive inefficiency that results in the loss of up to 12% of the host's dietary energy intake and a major contributor of methane as a greenhouse gas to the atmosphere. The potential for these compounds to inhibit the foodborne pathogens, Escherichia coli O157:H7 and Salmonella Typhimurium DT104, was also tested. The results from the present study revealed that anaerobically grown O157:H7 and DT104 treated with the methanogenic inhibitor, ethyl nitroacetate, at concentrations of 3 and 9 mM had decreased (p < 0.05) mean specific growth rates of O157:H7 (by 22 to 36%) and of DT104 (by 16 to 26%) when compared to controls (0.823 and 0.886 h-1, respectively). The growth rates of O157:H7 and DT104 were decreased (p < 0.05) from controls by 31 to 73% and by 41 to 78% by α-lipoic acid, which we also found to inhibit in vitro rumen methanogenesis up to 66% (p < 0.05). Ethyl nitroacetate was mainly bacteriostatic, whereas 9 mM α-lipoic acid decreased (p < 0.05) maximal optical densities (measured at 600 nm) of O157:H7 and DT104 by 25 and 42% compared to controls (0.448 and 0.451, respectively). In the present study, the other oxidized nitro and organosulfur compounds were neither antimicrobial nor anti-methanogenic.

Antagonistic Effects of Lipids Against the Anti-Escherichia coli and Anti-Salmonella Activity of Thymol and Thymol-β-d-Glucopyranoside in Porcine Gut and Fecal Cultures In Vitro

Strategies are sought to reduce the carriage and dissemination of zoonotic pathogens and antimicrobial-resistant microbes within food-producing animals and their production environment. Thymol (an essential oil) is a potent bactericide in vitro but in vivo efficacy has been inconsistent, largely due to its lipophilicity and absorption, which limits its passage and subsequent availability in the distal gastrointestinal tract. Conjugation of thymol to glucose to form thymol-β-d-glucopyranoside can decrease its absorption, but in vivo passage of effective concentrations to the lower gut remains suboptimal. Considering that contemporary swine diets often contain 5% or more added fat (to increase caloric density and reduce dustiness), we hypothesized that there may be sufficient residual fat in the distal intestinal tract to sequester free or conjugated thymol, thereby limiting the availability and subsequent effectiveness of this biocide. In support of this hypothesis, the anti-Salmonella Typhimurium effects of 6 mM free or conjugated thymol, expressed as log₁₀-fold reductions of colony-forming units (CFU) ml^-1, were diminished 90 and 58%, respectively, following 24-h in vitro anaerobic fecal incubation (at 39°C) with 3% added vegetable oil compared to reductions achieved during culture without added oil (6.1 log₁₀ CFU ml^-1). The antagonistic effect of vegetable oil and the bactericidal effect of free and conjugated thymol against Escherichia coli K88 tested similarly were diminished 86 and 84%, respectively, compared to reductions achieved in cultures incubated without added vegetable oil (5.7 log₁₀ CFU ml^-1). Inclusion of taurine (8 mg/ml), bile acids (0.6 mg/ml), or emulsifiers such as polyoxyethylene-40 stearate (0.2%), Tween 20, or Tween 80 (each at 1%) in the in vitro incubations had little effect on vegetable oil-caused inhibition of free or conjugated thymol. Based on these results, it seems reasonable to suspect that undigested lipid in the distal gut may limit the effectiveness of free or conjugated thymol. Accordingly, additional research is warranted to learn how to overcome obstacles diminishing bactericidal activity of free and conjugated thymol in the lower gastrointestinal tract of food-producing animals.

Nigella sativa L. as an alternative antibiotic feed supplement and effect on growth performance in weanling pigs

BACKGROUND

Nigella sativa L. (NS) is a plant containing bioactive constituents such as thymoquinone. Extracts of NS improve performance and reduce enteropathogen colonization in poultry and small ruminants, but studies with swine are lacking. In two different studies oral administration of NS extracts at doses equivalent to 0, 1.5 and 4.5 g kg^-1 diet was assessed on piglet performance and intestinal carriage of wildtype Escherichia coli and Campylobacter, and Salmonella Typhimurium.

RESULTS

Wildtype E. coli populations in the jejunal and rectal content collected 9 days after treatment began were decreased (P ≤ 0.05). Populations recovered from pigs treated with extract at 1.5 and 4.5 g kg^-1 diet were 0.72-1.31 log₁₀ units lower than the controls (ranging from 6.05 to 6.61 log₁₀ CFU g^-1 ). Wildtype Campylobacter and Salmonella Typhimurium were unaffected by NS treatment. Feed efficiency over the 9 days improved linearly (P < 0.05) from 3.88 with 0 NS-treated pigs to 1.47 and 1.41 with pigs treated with NS at 1.5 and 4.5 g kg^-1 diet, respectively, possibly due to high glutamine/glutamic acid content of the NS extract.

CONCLUSION

NS supplementation of weanling pigs improved feed efficiency and helped control intestinal E. coli during this vulnerable production phase. © 2017 Society of Chemical Industry.

Transabdominal and transrectal ultrasonography of fetuses in Württemberg ewes: Correlation with gestational age

It is useful to determine the gestational age in sheep to provide essential information for effective flock management practices. The aims of this study were to evaluate the efficacy and practical aspects for using two ultrasound techniques, transabdominal and transrectal, in determining the gestational age in Württemberg ewes. Monitoring of embryo and fetus developmental stages during the ewes' gestation was carried out with real time ultrasound using a transabdominal convex probe, frequency 3.5 MHz, and a transrectal linear probe, frequency 7.5 MHz. The size of the embryonic vesicle during the period from the 23rd to the 38th day of gestation can be used as a confirmational indicator of gestational age when the transrectal probe is used. The occipital nasal diameter correlated with the gestational age with both transabdominal (P < 0.05) and transrectal probes (P < 0.01) from the 46th to the 63rd day of gestation. The biparietal diameter of the fetal head measured by transabdominal probe during the period from the 46th to the 63rd day of gestation correlates with gestation age (P < 0.05). The diameter of the fetal eye orbit monitored by transrectal probe from the 46th to the 63rd day of gestation also correlated well with gestational age (P < 0.05).

Comparative effect of thymol or its glucose conjugate, thymol-β-D-glucopyranoside, on Campylobacter in avian gut contents

Campylobacter jejuni is an important human food-borne pathogen that can contaminate meat and poultry during processing. Consequently, strategies are sought to reduce the carriage of C. jejuni in food animals before they arrive at the abattoir. Thymol is a natural product that reduces survivability of Campylobacter in vitro, but its rapid absorption from the proximal alimentary tract limits its bactericidal efficacy in vivo. Thymol-β-D-glucopyranoside is more resistant to absorption than free thymol, but its administration to chickens has not been reported. In the present studies, 1 mM thymol-β-D-glucopyranoside was shown to exhibit near equal anti-Campylobacter activity as 1 mM thymol when incubated anaerobically in avian crop or cecal contents in vitro, resulting in reductions of 1.10-2.32 log10 colony forming units mL(-1) in C. jejuni concentrations after 24 h incubation. In a follow-up live animal study, oral administration of thymol-β-D-glucopyranoside, but not free thymol, significantly lowered (>10-fold) recovery of Campylobacter from the crop of market-aged broilers when compared to placebo-treated controls (n = 6 broilers/treatment). Neither thymol-β-D-glucopyranoside nor thymol affected recovery of Campylobacter from cecal contents of the treated broilers. These results indicate that rapid absorption or passage of free thymol from the crop precluded its anti-Campylobacter activity at this site and throughout the entire gastrointestinal tract. Conversely, lower recovery of Campylobacter from the crop of birds treated with thymol-β-D-glucopyranoside indicates this conjugate was retained and able to be hydrolyzed to biologically active free thymol at this site as intended, yet was not sufficiently protected to allow passage of efficacious amounts of the intact glycoside to the lower gut. Nevertheless, these results warrant further research to see if higher doses or encapsulation of thymol-β-D-glucopyranoside or similar glycosides may yield an efficacious additive to reduce carriage of Campylobacter as well as other pathogens throughout the avian gut.

Ex vivo absorption of thymol and thymol-β-D-glucopyranoside in piglet everted jejunal segments

Food-producing animals are reservoirs of Campylobacter, a leading bacterial cause of human foodborne illness. The natural product thymol can reduce the survivability of Campylobacter, but its rapid absorption in the proximal gastrointestinal tract may preclude its use as a feed additive to reduce intestinal colonization of these pathogens. This work examined the ex vivo absorption of thymol and thymol-β-d-glucopyranoside in everted porcine jejunal segments, as the latter was hypothesized to be more resistant to absorption. A modified gas chromatography and extraction method was developed to determine 1.0-500 mg/L thymol. From 1 and 3 mM solutions, 0.293 ± 0.04 and 0.898 ± 0.212 mM thymol, respectively, p = 0.0347, were absorbed, and 0.125 ± 0.041 and 0.317 ± 0.143 mM thymol-β-d-glucopyranoside, respectively, p = 0.0892, were absorbed. Results indicate that thymol-β-d-glucopyranoside was absorbed 2.3 to 2.8 times less effectively than thymol, thus providing evidence that thymol-β-d-glucopyranoside may potentially be used as a feed additive to transport thymol to the piglet lower gut.