Eight Hereford x Friesian steers prepared with rumen and duodenal cannulae were offered increasing proportions (increase of 33% each period) of red clover to grass over four periods with grass silage fed throughout to 4 steers as an experimental control. Numbers of Escherichia coli and Listeria were enumerated in silage from rumen, duodenal digesta and faecal samples at time points throughout each period. The results indicated that no silage contained E.coli whilst all silages had high populations of Listeria.  Pathogen populations were lowest in the duodenum and highest in the rumen, although large populations were also found in faeces.  The populations of E.coli were generally 10 fold lower than those of Listeria. Feeding red clover appeared to reduce pathogen loading but this was confounded by variation in the pathogen populations in the feed.  Thus in conclusion, further research is required to elucidate the different effects of red clover and feed pathogen load on the gut and faecal pathogen populations

Bakewell, Eleanor L.

Davies, David R.

Sanderson, Ruth

Bakewell, E. L.

Sanderson, R.

Davies, D. R.

Organic Eprints

3rd  QLIF Congress, Hohenheim, Germany, March 20-23, 2007 Archived at http://orgprints.org/view/projects/int_conf_qlif2007.html                                                   Effects of inclusion of red clover silage on the carriage of gut pathogens in steers  E L Bakewell1, R. Sanderson1 and, D R Davies1   Key words: Red Clover Silage, pathogens, steers, diet, faecal shedding. Abstract  Eight Hereford x Friesian steers prepared with rumen and duodenal cannulae were offered increasing proportions (increase of 33% each period) of red clover to grass over four periods with grass silage fed throughout to 4 steers as an experimental control. Numbers of Escherichia coli and Listeria were enumerated in silage from rumen, duodenal digesta and faecal samples at time points throughout each period. The results indicated that no silage contained E.coli whilst all silages had high populations of Listeria.  Pathogen populations were lowest in the duodenum and highest in the rumen, although large populations were also found in faeces.  The populations of E.coli were generally 10 fold lower than those of Listeria. Feeding red clover appeared to reduce pathogen loading but this was confounded by variation in the pathogen populations in the feed.  Thus in conclusion, further research is required to elucidate the different effects of red clover and feed pathogen load on the gut and faecal pathogen populations. Introduction  Despite recent public health scares associated with pathogenic bacteria such as Listeria, verotoxigenic Escherichia coli (VTEC’s) plus numerous other potentially hazardous micro-organisms they are still often low in priority for control and remediation. Nevertheless, in the UK and USA several outbreaks of gastro-enteritis in humans have been sourced to livestock operations and the link between disease and livestock production is well documented (Pell, 1997). In the case of Escherichia coli 0157:H7 less than 700 cells (Tuttle et al., 1999) and as few as 10 are required to cause human disease which is frequently associated with food borne disease resulting from beef and milk products yet is rarely associated with animal disease. Little work has focused on the control and eradication of E.coli 0157:H7 in the animal on farm and this must be the primary point for combating the problem.  Listeria monocytogenes is a well documented pathogen as a main contaminant of forage (Fenlon et al., 1989). It can survive and multiply during ensiling and storage, even where there is a very low oxygen concentration during the silage fermentation process (Donald et al., 1995). At feed-out where silage is exposed to oxygen the rise in pH often causes a rise in the numbers of Listeria.  There are a number of factors that need to be investigated to assess the significance of pathogenic organisms and to elucidate critical points to break the cycle of contamination and thus reduce the pathogen load within the cycle. Waste manure and sewage sludge added to land to enrich the soil with nutrients and promote crop growth  1 Institute of Grassland and Environmental Research, Plas Gogerddan, Aberystwyth SY23 3EB UK E-mail david.davies@bbsrc.ac.uk, Internet www.iger.bbsrc.ac.uk   Archived at http://orgprints.org/9826/   3rd  QLIF Congress, Hohenheim, Germany, March 20-23, 2007 Archived at http://orgprints.org/view/projects/int_conf_qlif2007.html   still contain pathogens in high numbers and these lead to contamination of soil and crops. The animals then consume contaminated grazed or ensiled forages. These pathogens then enter the gut, multiply and are deposited in faeces. Humans may then become infected by direct contact with the contaminated animal or by consuming infected meat and dairy products. It is this faecal shedding that results in environmental and food contamination and methods need to be found to reduce these processes.  Red clover and grass/clover-based forages are already widely used in feed rations for beef cattle and dairy cows. Red clover is a mainstay of organic rotations in many systems and its N fixation is an important source of N for low input and organic systems. There is limited evidence to suggest that Red Clover may impact negatively on pathogen growth (Garber et al., 1995). Furthermore, components such as Formenonetin in red clover have been shown to inhibit E.coli in laboratory cultures (Duncan et al., 2000). This study aims to investigate this effect further. Materials and methods  Eight Hereford x Friesian steers (300kg approx. weight) prepared with rumen and duodenal cannulae were offered either perennial ryegrass (Lolium perenne) silage throughout or an increasing mix of a red clover (Trifolium pratense) silage (RC): perennial ryegrass silage (G). The experiment was a continual design consisting of 4 periods of 21 days 4 animals were maintained on a grass silage diet throughout and a further 4 animals received grass silage in period 1 then G66:RC33, G33:RC66, RC100 in periods 2-4 respectively. Due to the simple nature of the diets, dietary treatments (silages) were switched from one to the other with immediate effect, with no gradual changeover. The animals were housed in individual pens and had access to fresh water and salt licks (Rockies) throughout. Animals received their daily food allocation in two equal meals at 08.30 and 15.30. Refusals if any were removed before early morning feed and dry-matter (DM) intake determined.  Microbial analysis Rumen, faecal and duodenal digesta were collected post early morning feed on days 0,1,2,4,8,16 and 21 and enumerated for Listeria monocytogenes using Listeria Isolation Medium (LAB M) and total Escherichia.coli and E.coli 0157 using Sorbitol McConkey with B.C.I.G Agar (OXOID). Results  Whilst the forage fed to the steers had no detectable E. coli at any time during the 12 week experimental period there was a large and variable population of Listeria associated with it.  The grass silage over the 12 week period had a mean of 1.12 x 107 CFU/g DM (minimum 1.11 X 105; maximum 1.17 x 107 CFU/g DM), whilst the feed containing various proportions of red clover had at least 10 fold fewer Listeria at 1.2 x 106 CFU/g DM (minimum 3.16 X 104; maximum 1.05 x 107 CFU/g DM).  The results also showed that greater the red clover inclusion level the lower the Listeria population with populations of 3.6 x 106 and 2.2 x 105 CFU/g DM respectively for diets containing 33:66 grass:red clover or 100 % red clover. Thus it is likely that the level of Listeria load on the forage fed will have had a confounding effect on the populations of Listeria present in the digesta and faeces of the animals consuming it. 3rd  QLIF Congress, Hohenheim, Germany, March 20-23, 2007 Archived at http://orgprints.org/view/projects/int_conf_qlif2007.html The figures show the variation over time in rumen (Figs 1a and b) and faeces (Figs 2a and b) of populations of E. coli and Listeria. The results are shown for all 8 animals  used in the experiment and thus considerable time dependant variation within each animal can be seen.  However in general all animals follow the same trend but it must be noted that by increasing the level of inclusion of red clover in the diet Listeria numbers tend to decline in all animals on this treatment.              Figure 1 Variation in populations of E.coli (a) and Listeria (b) in the rumen of steers fed either grass silage (solid lines) or increasing proportions of red clover silage (dotted lines) with time over a 12 week period.            Figure 2 Variation in populations of E.coli (a) and Listeria (b) in the faeces of steers fed either grass silage (solid lines) or increasing proportions of red clover silage (dotted lines) with time over a 12 week period.  Discussion The results indicate that there is considerable variation in shedding of pathogens with time over the 12 week experimental period.  There appeared to be a reduction in the faecal shedding (Figure 2b) of Listeria with increased incorporation of red clover in the 3rd  QLIF Congress, Hohenheim, Germany, March 20-23, 2007 Archived at http://orgprints.org/view/projects/int_conf_qlif2007.html   diet, whereas the effect on E.coli was less marked.  However, there was also considerable variation in the load of both E. coli and Listeria entering with the feed.  It is highly probable that the burden of bacterial pathogens entering the mouth affects the magnitude of the pathogen populations present both in gut digesta and faeces. Conclusions The results outlined above do not give a clear indication of how diet may influence food borne pathogens in the gut of ruminants.  Within this experiment two factors appear to be contributing to the pathogen load in gut digesta and faeces these are pathogen load of the feed as fed and in the case of Listeria the proportion of red clover in the diet. Further work is required to elucidate which of these factors is exerting the biggets effect before practical on farm approaches to reduce pathogen carriage by ruminants can be introduced.  Acknowledgments The authors would like to thank Martin Leyland and Naomi Ellis at IGER Trawscoed for the care of the animals and Mark Scott for his excellent laboratory skills. This work was carried out with funding from the EU framework VI QLIF project and the Department for Environment, Food and Rural Affairs. References  Duncan, S.H., Booth, I.R., Flint, H.J. and Stewart, C.S. (2000). The potential for the control of Escherichia coli O157 in farm animals. Journal of Applied Microbiology Symposium Supplement, 88: 157S-165S Donald, A.S., Fenlon D.R., Seddon B. (1995). The relationship between ecophysiology, indigenous microflora and growth of Listeria monocytogenes in grass silage. Journal of Applied Bacteriology, 79: 141-148 Fenlon, D.R., Wilson J., Weddell J.R. (1989). The relationship between spoilage and Listeria monocytogenes contamination in bagged and wrapped big bale silage. Grass and Forage Science 44: 97-100 Garber, L.P., Wells, S.J., Hancock, D.D., Doyle, M.P.,Tuttle, J., Shere, J.A. and Zhao, T. (1995). Risk factors for faecal shedding of Escherichia coli 0157:H7 in dairy calves.  Journal of the American Veterinary Medicine Association 207: 46 – 49.  Pell, A.N. (1997). Manure and microbes: Public and animal health problem? Jouornal of Dairy Science 80: 2673-2681 Tuttle, J. Gomez, M., Doyle, M.P., Wells, J.G., Zhao, T., Tauxe, R.V. and Griffin, P.M. (1999). Lessons from a large outbreak of Escherichia coli 0157:H7 infections: insights into the infectious dose and method of widespread contamination of hamburger patties. Epidemiology and Infection 122: 185-192  

Effects of inclusion of red clover silage on the carriage of gut pathogens in steers

Abstract

Similar works

Full text

Available Versions

Organic Eprints