Yong Soo Jung

Effect of select nitrocompounds on ruminal fermentation; an initial look at their potential to reduce economic and environmental costs associated with ruminal methanogenesis

Methane production by ruminal microbes during the digestion of feedstuffs is an inefficient process resulting in losses of 2-12% of the gross energy consumed by ruminants. Presently, we report the effect of three inhibitors on ruminal methane production in vitro. Mixed populations of ruminal microbes collected from cannulated cows maintained on an alfalfa hay:corn diet (50:50) were incubated at 39 degrees C for 24 h under a 100% carbon dioxide gas phase in closed tubes with 72 mM added sodium formate. Cultures were supplemented with 12 mM 2-nitropropanol, nitroethane or nitroethanol (experiment 1) or with 2, 12 or 24 mM nitroethane or a combination of 12 mM nitroethane and 4 mM nitroethanol (experiment 2). Control cultures containing no added nitrocompound were incubated simultaneously with treated incubations. Methane concentrations were reduced (P<0.05) from those measured in control incubations (27.6 +/- 2.1 and 17.7 +/- 0.8 micromol/ml; mean +/- SD for experiments 1 and 2, respectively) by at least 57% and as much as 94% in the nitrocompound supplemented incubations. By comparison, the widely fed methane inhibitor, monensin, typically reduces ruminal methane production by about 33%. Concentrations of volatile fatty acids and ammonia that accumulated in the nitrocompound supplemented incubations were not markedly affected compared to those produced by control cultures despite the reductions in methane produced. Hydrogen accumulated only slightly in cultures supplemented with the nitrocompounds. These results demonstrate that 2-nitropropanol, nitroethane and nitroethanol inhibit ruminal methane production. Further research is warranted to determine the mechanisms responsible for this inhibition and to see if these inhibitors can be used in practical application to reduce economic and environmental costs associated with ruminal methanogenesis.

Reduction of Salmonella Typhimurium in experimentally challenged broilers by nitrate adaptation and chlorate supplementation in drinking water.

The effects of two feed supplements on Salmonella Typhimurium in the ceca of market-age broilers were determined. Broilers orally challenged 6 days before slaughter with a novobiocin- and nalidixic acid-resistant strain of Salmonella Typhimurium were divided into one of four groups (20 birds each). The first group (the control group) received no treatment, the second group received sodium nitrate (SN) treatment (574 mg of NaNO3 per kg of feed), the third group received experimental chlorate product (ECP) treatment (15 mM NaClO3 equivalents), and the fourth group received ECP treatment in combination with SN treatment. The SN treatment was administered via feed for 5 days immediately before slaughter, and ECP was provided via ad libitum access to drinking water for the last 2 days before slaughter. Cecal contents were subjected to bacterial analysis. Significant (P < 0.05) Salmonella Typhimurium reductions (ca. 2 log units) relative to levels for untreated control broilers were observed for broilers receiving ECP in combination with SN. The ECP-only treatment resulted in significant (P < 0.05) reductions (ca. 0.8 log) of Salmonella Typhimurium in trial 2. We hypothesize that increasing Salmonella Typhimurium nitrate reductase activity resulted in increased enzymatic reduction of chlorate to chlorite, with a concomitant decrease in cecal Salmonella Typhimurium levels. On the basis of these results, preadaptation with SN followed by ECP supplementation immediately preharvest could be a potential strategy for the reduction of Salmonella Typhimurium in broilers.

Experimental use of 2-nitropropanol for reduction of Salmonella Typhimurium in the ceca of broiler chicks

The effect of 2-nitropropanol (2NPOH) administration on Salmonella enterica serovar Typhimurium in experimentally infected chicks was determined. Chicks orally challenged with 10(6) CFU/ml of a novobiocin- and naladixic acid-resistant Salmonella Typhimurium at 6 days of age were divided into three groups receiving 0 (control), 6.5, and 13 mg 2NPOH per bird (experiment 1) or four groups receiving 0 (control), 13, 65, and 130 mg 2NPOH per bird (experiment 2). Treatments were administered orally 1 day post-Salmonella challenge. Cecal contents collected at necropsy 24 and 48 h after treatment were subjected to bacterial and volatile fatty acid (VFA) analysis. In experiment 1, concentrations (mean+/-SD log CFU per g) of Salmonella were reduced (P < 0.05) in the group administered 13 mg 2NPOH per bird at both the 24- and 48-h samplings compared with the controls (2.58+/-2.10 versus 4.64+/-1.79 and 2.88+/-2.78 versus 5.03+/-2.42 at 24 and 48 h, respectively). In experiment 2, mean+/-SD populations of Salmonella were reduced (P < 0.05) in all groups receiving 2NPOH compared with untreated controls (3.65+/-2.01, 3.39+/-2.42, and 3.47+/-1.55 at 13, 65, and 130 mg, respectively, versus 6.09+/-1.02). Propionate concentrations were reduced (P < 0.05) by the 13-mg 2NPOH per bird treatment. Total VFA concentrations from the group treated with 13 mg 2NPOH per bird were lower (P < 0.05) by 48, but not 24, hours posttreatment than those from the group treated with 6.5 mg 2NPOH per bird. These results demonstrate the inhibitory activity of 2NPOH against Salmonella Typhimurium in vivo.

Effect of Drinking-Water Administration of Experimental Chlorate Ion Preparations on Salmonella enterica serovar Typhimurium Colonization in Weaned and Finished Pigs

Foodborne disease caused bySalmonella is of public health and economic significance. In order to assess the practical effectiveness of a new intervention strategy, experimental chlorate preparations (ECP) were administered via the drinking water to weaned and finished pigs that had been orally challenged the previous day with 109–1010 colony-forming units ofSalmonella serovar Typhimurium. After 24 or 36 had libitum access to 0X, 1X or 2X ECP treatment (where X is the concentration estimated to deliver a minimal daily effective dose), the pigs were euthanized and gut contents and lymph tissue collected at necropsy were cultured for the challengeSalmonella. Drinking water administration of ECP effectively reduced (p<0.05) caecalSalmonella concentrations and, with the weaned pigs, tended (p≤0.10) to reduce rectalSalmonella concentrations. No negative effects of ECP treatment on water intake and animal wellbeing were observed and only marginal effects on gut fermentation characteristics occurred. The bactericidal effect of administering ECP in drinking water was relatively rapid, with reductions in caecalSalmonella concentrations occurring within 24 h. These results suggest that ECP administered to pigs just days before slaughter may reduce gut concentrations ofSalmonella; however, the impacts of such reductions on slaughter hygiene have yet to be determined.

Inhibitory activity of 2-nitropropanol against select food-borne pathogens in vitro*

Aims:  To test the inhibitory activity of 2‐nitro‐1‐propanol (2NPOH) against Salmonella Typhimurium, Escherichia coli O157:H7 and Enterococcus faecalis.

Inhibitory effect of select nitrocompounds on growth and survivability of Listeria monocytogenes in vitro.

We report the effects of 2-nitro-1-propanol (2NPOH), 2-nitroethanol (2NEOH), and nitroethane (NE) on growth and survivability of Listeria monocytogenes. In all cases, inhibition was greatest with 2NPOH and least with NE. For example, specific growth rates of L. monocytogenes strain 18 declined (P < 0.05) 76, 60, and 29% from controls during aerobic culture at 37 degrees C in brain heart infusion broth containing 10 mM 2NPOH, 2NEOH, or NE, respectively. Mean specific growth rate for the controls incubated likewise without added nitrocompound was 0.62 +/- 0.02 h(-1). Specific growth rates of L. monocytogenes Scott A decreased (P < 0.05) 67, 45, and 11%, respectively, from controls (0.67 +/- 0.02 h(-1)) when cultured similarly. Specific growth rates for L. monocytogenes strain 18 incubated similarly except at 30 degrees C were reduced (P < 0.05) 76, 60, and 30%, respectively, and were reduced (P < 0.05) 78, 23, and 23% during anaerobic culture at 30 degrees C in brain heart infusion broth containing 15 mM 2NPOH, 2NEOH, or NE (control rates ranged from 0.37 +/- 0.07 to 0.74 +/- 0.05 h(-1)). Survivability of L. monocytogenes strain 18 was reduced (P < 0.05) during aerobic storage (4 months at 4 degrees C) in brain heart infusion broth containing 2NPOH or 2NEOH (by 7.8 and 1.9 log units, respectively) but not NE. The inhibitory effect of 2NPOH was approximately 20% greater during growth at pH 7.0 than at pH 5.6 or 8.0. These results demonstrate the differential inhibitory activity of 2NPOH, 2NEOH, and NE against L. monocytogenes in vitro.