College of Agriculture & Natural Resources
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The collections in this community comprise faculty research works, as well as graduate theses and dissertations.
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Item Changes in various metabolic parameters in blood and milk during experimental Escherichia coli mastitis for primiparous Holstein dairy cows during early lactation(Springer Nature, 2014-10-17) Moyes, Kasey M; Larsen, Torben; Sørensen, Peter; Ingvartsen, Klaus LThe objective of this study was to characterize the changes in various metabolic parameters in blood and milk during IMI challenge with Escherichia coli (E. coli) for dairy cows during early lactation. Thirty, healthy primiparous Holstein cows were infused (h = 0) with ~20-40 cfu of live E. coli into one front mammary quarter at ~4-6 wk in lactation. Daily feed intake and milk yield were recorded. At –12, 0, 3, 6, 12, 18, 24, 36, 48, 60, 72, 96, 108, 120, 132, 144, 156, 168, 180 and 192 h relative to challenge rectal temperatures were recorded and quarter foremilk was collected for analysis of shedding of E. coli. Composite milk samples were collected at -180, -132, -84, -36, -12, 12, 24, 36, 48, 60, 72, 84, 96, 132 and 180 h relative to challenge (h = 0) and analyzed for lactate dehydrogenase (LDH), somatic cell count, fat, protein, lactose, citrate, beta-hydroxybutyrate (BHBA), free glucose (fglu), and glucose-6-phosphate (G6P). Blood was collected at -12, 0, 3, 6, 12, 18, 24, 36, 60, 72, 84, 132 and 180 h relative to challenge and analyzed for plasma non-esterified fatty acids (NEFA), BHBA and glucose concentration. A generalized linear mixed model was used to determine the effect of IMI challenge on metabolic responses of cows during early lactation. By 12 h, E. coli was recovered from challenged quarters and shedding continued through 72 h. Rectal temperature peaked by 12 h post-challenge and returned to pre-challenge values by 36 h post-IMI challenge. Daily feed intake and milk yield decreased (P <0.05) by 1 and 2 d, respectively, after mastitis challenge. Plasma BHBA decreased (12 h; P <0.05) from 0.96 ± 1.1 at 0 h to 0.57 ± 0.64 mmol/L by 18 h whereas concentration of plasma NEFA (18 h) and glucose (24 h) were significantly greater, 11 and 27%, respectively, after challenge. In milk, fglu, lactose, citrate, fat and protein yield were lower whereas yield of BHBA and G6P were higher after challenge when compared to pre-challenge values. Changes in metabolites in blood and milk were most likely associated with drops in feed intake and milk yield. However, the early rise in plasma NEFA may also signify enhanced adipose tissue lipolysis. Lower concentrations of plasma BHBA may be attributed to an increase transfer into milk after IMI. Decreases in both milk lactose yield and % after challenge may be partly attributed to reduced conversion of fglu to lactose. Rises in G6P yield and concentration in milk after challenge (24 h) may signify increased conversion of fglu to G6P. Results identify changes in various metabolic parameters in blood and milk after IMI challenge with E. coli in dairy cows that may partly explain the partitioning of nutrients and changes in milk components after IMI for cows during early lactation.Item Investigating Metrics Proposed to Prevent the Harvest of Leafy Green Crops Contaminated by Floodwater(2015) Callahan, Mary Theresa; Buchanan, Robert L; Food Science; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Pathogens can be transported by water through soil to contaminate distant crops. The California LGMA states that leafy green crops within 30ft of flooded soil should be destroyed due to potential contamination. Previously flooded areas should not be replanted for 60 days. This study investigated the transport of Salmonella enterica and Citrobacter freundii through soil in a model system with a positive slope (uphill). Field trials involving flooding one end of a spinach bed with a negative slope (downhill) with water containing Escherichia coli were also conducted. Soil type, soil moisture content, and slope affected bacterial movement. In field trials, E. coli was quickly transported to the 30ft boundary, and persisted significantly longer in the fall trial than the spring. These data suggest the LGMA metrics need to provide additional parameters to prevent the harvest of leafy green crops potentially contaminated by floodwater.Item Intervention Strategies for Escherichia coli O157:H7 and Salmonella in Organic Soil and on Fresh Produce(2012) Nguekam Yossa, Irene Nadine; Lo, Martin; Food Science; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Recently, foodborne diseases caused by Escherichia coli O157:H7 and Salmonella have been increasingly associated with the consumption of fresh produce. Consumers' demand for safe, natural products has led to research on natural antimicrobials for effective control of foodborne pathogens on fresh produce, which can be inadvertently contaminated by soil. Therefore, there is a need to control microbial loads in soil to minimize contamination. The objectives of this study were to evaluate the antimicrobial activity of cinnamaldehyde, Ecotrol®, eugenol, Sporan® and acetic acid against E. coli O157:H7 and Salmonella in organic soil, and to evaluate the antimicrobial effects of cinnamaldehyde and Sporan® alone, or in combination with acetic acid against E. coli O157:H7, Salmonella, and the native microflora of iceberg, romaine and spinach leaves. The quality parameters of the treated fresh produce were monitored, whereas the modes of action of cinnamaldehyde and Sporan® were investigated. The results showed that cinnamaldehyde had the highest bactericidal activity against E. coli O157:H7 and Salmonella in organic soil. Increases in oil concentration resulted in further reduction of both microorganisms. Up to 5 and 6 log CFU/g of E. coli O157:H7 and Salmonella, respectively, were reduced with 2% Sporan® and acetic acid after 24 h. Sporan® in combination with acetic acid (1000SV) and 800 ppm cinnamaldehyde-Tween reduced significantly E. coli O157:H7 (~3 log CFU/g) on iceberg and spinach leaves following treatment at day 0. Likewise, 1000SV treatment reduced Salmonella ~ 2.5 log CFU/g at day 0. E. coli O157:H7 and Salmonella populations in treated iceberg, spinach and romaine leaves were reduced during storage at 4°C. The native microflora of untreated and treated spinach and lettuce leaves increased during the storage time. The texture and the color of iceberg, romaine and spinach leaves treated with essential oils were not significantly different from the control lettuce after 14 days. The scanning and transmission electron microscopy of oil-treated bacterial cells indicated possible cell structural damage and leakage of cellular content. This study shows the potential use of essential oils to effectively reduce E. coli O157:H7 and Salmonella populations in soil and on fresh produce without adversely affecting leaf color and texture.