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Title: Impacts of dietary forage and crude protein levels on the shedding of Escherichia coli O157:H7 and Listeria in dairy cattle feces

item BISWAS, S - University Of California
item NIU, M - University Of California
item APPUHAMY, J.A.D.R.N. - University Of California
item Leytem, April
item Dungan, Robert - Rob
item KEBREAB, E - University Of California
item PANDEY, P - University Of California

Submitted to: Livestock Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/29/2016
Publication Date: 12/1/2016
Publication URL:
Citation: Biswas, S., Niu, M., Appuhamy, J., Leytem, A.B., Dungan, R.S., Kebreab, E., Pandey, P. 2016. Impacts of dietary forage and crude protein levels on the shedding of Escherichia coli O157:H7 and Listeria in dairy cattle feces. Livestock Science. 194:17-22.

Interpretive Summary: Escherichia coli O157:H7 and L. monocytogenes are two common pathogenic bacteria associated with ruminant animals. This study quantified these bacteria in dairy manure from cows fed diets differing in dietary forage and crude protein levels. There was a significant impact of dietary forage and protein levels on the concentration of L. monocytogenes in feces. Although there was significant forage and protein interactions for fecal E.coli O157:H7, it was not significant for L. monocytogenes. Our results indicate that forage and CP levels in animal feed have the potential to influence the fecal shedding of pathogens from dairy cattle. Although it may not be possible to eliminate pathogenic bacteria from dairy manure, efforts should put toward best manure management practices. Before that, optimal diet combinations should be investigated to reduce/control their excretion, while considering the ultimate output (quality of meat/dairy) and economic significance.

Technical Abstract: Shedding of Escherichia coli O157:H7 and Listeria monocytogenes in ruminant manure is well reported. However, the influence of dietary manipulation on the shedding of the pathogens is not well understood. This study was conducted to improve the understanding of the relationship between dietary feed composition and pathogen shedding in dairy feces, particularly E. coli O157:H7 and L. monocytogenes. Twelve cows were randomly assigned to a 2 × 2 factorial arrangement of 2 dietary forage levels: low forage (37.4% of dry matter [DM]) vs. high forage (HF, 53.3% of DM) and two dietary crude protein (CP) levels: low protein (LP, 15.2% of DM) vs. high protein (HP, 18.5% of DM) in a 4 × 4 replicated Latin square design with four periods each including 15 d adaptation and 3 d sample collection. In CP treatments, significantly low concentrations of L. monocytogenes were observed from cows fed the HP (0.9-1.6 log10 cfu/g) compared to the LP diet (1.3–2.1 log10 cfu/g). Significant interaction effect was observed between dietary forage and crude protein on the presence of E. coli O157:H7 (P < 0.05) but not on L. monocytogenes. On average, the highest E. coli O157:H7 concentration (6.5 log10 cfu/g of feces) was observed from the HF and HP diet and the lowest concentration was 6.2 log10cfu/g from the HF and LP diet. The average L. monocytogenes shedding was within the range of 1.8 to 2.4 log 10cfu/g among the treatments. The study showed that diet has an influence on the shedding of pathogenic bacteria in dairy excreta.