Browsing by Author "Geornaras, Ifigenia, committee member"
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Item Embargo A comprehensive study of Salmonella infections and microbial analysis of probiotics on beef cattle(Colorado State University. Libraries, 2023) Thompson, Tyler Warren, author; Nair, Mahesh Narayanan, advisor; Geornaras, Ifigenia, committee member; Belk, Keith, committee member; Noyes, Noelle, committee member; Morley, Paul, committee memberNon-typhoidal Salmonella remains a significant concern for food safety in the United States, causing millions of infections, hospitalizations, and deaths yearly. The Healthy People 2030 initiative set forth by the U.S. Department of Health and Human Services aims to address this issue by establishing goals and objectives for national health promotion and disease prevention, including two objectives focused on Salmonella control in the food supply. The recent declaration of Salmonella as an adulterant in certain poultry products by the U.S. Department of Agriculture further highlights the urgency of this issue. To align with the Healthy People 2030 goals and achieve a 25% reduction in salmonellosis, the U.S. Department of Agriculture's Food Safety and Inspection Service (FSIS) implemented new performance standards for beef products. However, such policies must be supported by quantitative microbial risk assessments (QMRA) to determine their impact on Salmonella infections. Therefore, these analyses would benefit from a systematic review examining existing literature on Salmonella, considering factors such as illness rates, exposure, and bacterial loads. This review included 42 articles that provided data necessary for fitting a dose-response model to empirical data that describes how dose, virulence group, and food vector affect illness (attack) rates. Results from the mixed-effects logistic regression model showed significant impacts of log dose consumed, virulence group, and food vector on illness rates. Notably, Salmonella serogroups of "Higher" virulence were found to be associated with greater odds of illness than "Lower" virulence strains. The study highlights the need for improved data reporting and standardized outbreak investigations to enhance the fitting of models to outbreak data. By considering factors like serovar group and food vector in the modeling process, regulators can demonstrate what influences attack rate to frame more effective food safety policies. In conclusion, this systematic review provides valuable insights into Salmonella infection risk from food sources and emphasizes the importance of evidence-based policies to reduce the burden of Salmonella-related illnesses and improve food safety in the United States. Liver abscesses in beef cattle are a common problem associated with highly-fermentable carbohydrate diets during finishing, leading to decreased production efficiency and aggregate carcass value. Dietary antimicrobial supplementation, such as tylosin, helps to control liver abscesses but raises concerns about selection for antimicrobial resistance. This study examined the impact of a probiotic mixture of propionic and lactic acid bacteria on microbial communities and antimicrobial resistance genes (ARGs) in fecal and liver abscess samples from beef cattle alongside Salmonella populations of mesenteric lymphatic tissues. Treatment diets fed in this study included a probiotic mixture alone (DFM), inclusion of Tylosin (TYL), a combination of including both (DFM+TYL), and a control group diet that did not include any supplements (CON). Fecal samples were collected at the time that feeding started, and then 28 d before arriving at the abattoir, where liver abscesses and mesenteric lymph nodes were sampled. Fecal and liver abscess samples were subjected to 16S rRNA and targeted enriched shotgun metagenomics to evaluate microbial communities and resistance genes of bacteria present. A portion of the liver abscess and mesenteric lymph nodes were tested for presence of Salmonella using PCR with further analysis of enumeration and serotype classification for mesenteric lymph nodes. Results showed no differences (P > 0.05) between the fecal microbiomes of the different treatment groups, and the addition of tylosin or probiotic mixture did not impact the fecal resistome. Similarly, no differences (P > 0.05) were observed between the liver abscess microbiomes of the different (P > 0.05) treatment groups, with Fusobacteria and Bacteroidetes being the dominant phyla in liver abscesses. Results indicated that incorporating DFMs did not affect Salmonella prevalence in the cattle's mesenteric lymph nodes or liver abscesses. Presence of Salmonella was found at low levels in only 22% of samples (91 positive out of 503 samples), just below 1 log CFU/g, and was predominantly represented by the C1 serogroup in mesenteric lymph nodes. These findings suggest that while diet interventions may not have a substantial impact, Salmonella can colonize mesenteric lymphatic tissues in cattle at low frequencies and concentrations. Treatment groups tested had no impact (P > 0.05) on fecal and liver abscesses microbiomes and resistance gene presence, along with no impact on Salmonella prevalence in liver abscesses or mesenteric lymphatic tissues.Item Open Access Association between beef ribeye area measurements and steak portion size(Colorado State University. Libraries, 2024) Schiefelbein, Abbey Faith, author; Nair, Mahesh N., advisor; Geornaras, Ifigenia, committee member; Clark, Daniel, committee member; Hess, Ann, committee memberAs cattle weights have increased over the past decades, hot carcass weight and ribeye area (REA) have also increased. The REA is an important determinant of carcass value as it impacts the thickness of steaks when portioned to a pre-determined weight. Additionally, previous research has indicated that steak thickness impacts consumers' eating experience potentially due to its impact on the degree of doneness. The objective of this study was to examine the relationship between carcass REA and steak portion size. Beef carcasses (n = 100) were selected from a commercial beef harvesting facility based on REA in 1 in2 (6.45 cm2) increments ranging from less than 11 in2 (70.97 cm2) to greater than 19 in2 (122.58 cm2) based on a United States Department of Agriculture-approved camera (E+V) with 10 total categories. Data (hot carcass weight, back fat thickness, and marbling) were collected from each selected carcass. The REA measurements were obtained using the grading camera, a manual grid, and pen tracing and measured using ImageJ software. Strip loins (IMPS#180) from selected carcasses were collected, and weight, length, and three width (anterior, middle, and posterior) measurements of the strip loins were measured manually. Each strip loin was then scanned through a Marel I-Cut 56 portion cutter to determine the thickness of 12 oz (340.19 g) and 16 oz (453.59 g) portions and to determine the weight of a 1-in (2.54 cm) thick portion. To quantify and describe the relationship between steak thickness (cut to 12 oz and 16 oz portions) and steak weight (cut at 1-in. thickness), linear regression models were developed using traced REA as the independent variable. Additionally, more exhaustive linear regression models were developed to predict steak thickness or weight based on the traced REA, hot carcass weight, fat thickness, strip loin weight, strip loin length, strip loin width, and average maximum height of the strip loin. Each model was evaluated separately for the main effects of each variable, with significance determined at ɑ=0.05. There was a significant (P < 0.001) correlation and linear relationship (P < 0.05) between traced REA measurement and 12 oz (R2 = 0.71), 16 oz (R2 = 0.71), and 1-in.-thick (R2 = 0.75) portions examined in this study. For 12 oz steaks, the steak thickness decreased by an estimated 0.055 in. (0.14 cm) for every 1-in. increase in REA. Similarly, for the 16 oz steaks, the steak thickness decreased by an estimated 0.074 in. (0.19 cm) for every square in. increase in REA. The 1-in. steak portions had a mean weight of 340 g, and the steak weight increased an estimated 18 g for each square in. increase in REA. In addition, using the strip loin measurements, linear regression models were able to predict steak thickness for 12 oz and 16 oz portions with an R2 of 0.95 each and predict the steak weight for the 1-in. portion with an R2 of 0.98. As expected, REA strongly correlated with the portion size of strip loin steaks cut to a specified weight or thickness. Additionally, our results indicated that the weight and length of the strip loin were good predictors of steak thickness (for 12 oz and 16 oz portions) or steak weight (for 1-in.-thick portions). Further research exploring consumer acceptance and degree of doneness for steaks with varying thicknesses would provide data to determine REA ranges and targets that would optimize steak portion sizes and consumer acceptability.Item Open Access Effects of antimicrobial interventions on food safety and an assessment of the Colorado pork supply(Colorado State University. Libraries, 2018) Britton, Brianna C., author; Woerner, Dale R., advisor; Belk, Keith E., advisor; Geornaras, Ifigenia, committee member; Prenni, Jessica E., committee memberTo view the abstract, please see the full text of the document.Item Open Access Effects of antimicrobial treatments on food safety, quality and shelf-life of beef(Colorado State University. Libraries, 2019) Swenson, Joanna Kristine, author; Belk, Keith E., advisor; Woerner, Dale R., advisor; Geornaras, Ifigenia, committee member; Narayanan Nair, Mahesh, committee member; Prenni, Jessica E., committee memberTo view the abstract, please see the full text of the document.Item Open Access Investigating the impact of the microbiome on beef steak color stability(Colorado State University. Libraries, 2022) Smith, Colton Levi, author; Nair, Mahesh N., advisor; Morgan, J. Brad, committee member; Geornaras, Ifigenia, committee member; Weir, Tiffany, committee member; Metcalf, Jessica L., committee member; Clark, Daniel L., committee memberMeat color is the most influential characteristic for consumer purchasing decisions. In fact, consumer discrimination of discolored beef results in approximately $3.73 billion/year lost in revenue in the US. Interestingly, most often these products are not yet microbially spoiled, leading to unnecessary food waste. Complicating matters, different muscles originating from the same carcass discolor at different rates. Several studies have investigated the physiochemical, enzymatic, and intrinsic muscle properties of muscles with differing color stabilities such as color stabile beef longissimus lumborum (LL) and color labile psoas major (PM). However, the impact of microbial growth on the meat color stability has not been investigated yet. Therefore, the objective of this study was to characterize the microbial populations and their biochemical parameters of color labile and color stabile beef muscle cuts during aerobic retail display. Paired USDA Select LL and PM (n = 5) were collected from a local abattoir and aged for 14 days in darkness under vacuum at 3°C. After aging, the muscles were fabricated into 2.54-cm thick steaks and packaged aerobically in a foam tray wrapped with polyvinyl chloride film. Steaks were then placed into an open faced multi-decked retail display case for 7 days at 4°C ± 1°C. Each day, beginning day of fabrication, steaks were evaluated for visual color, percentage discoloration, instrumental color, water activity, pH, metmyoglobin reducing activity, microbial levels as determined by using culture-dependent methods (aerobic plate counts, lactic acid bacteria plate counts, Pseudomonas spp. plate counts and Enterobacteriaceae plate counts), and 16S rRNA bacterial gene sequencing (microbiome). Visual color was darker (P < 0.05) for PM than LL for all days, and percentage discoloration was greater (P < 0.05) for PM than LL from the second daif retail display. Color stability (determined by MRA) was greater (P > 0.05) in LL compared to PM for all days. The pH was greater (P < 0.05) for PM for the first 5 days of display compared to LL. However, water activity was the same (P > 0.05) for both muscles across all display days. Microbiological analyses revealed that aerobic plate counts, and lactic acid bacteria plate count were greater (P < 0.05) for PM starting on day 1 of display compared to LL. The Pseudomonas spp. plate counts were similar (P > 0.05) until day 2, after which PM was greater (P < 0.05) than LL and remained greater for the remaining days. Moreover, the 16S rRNA gene sequencing showed no differences (P > 0.05) in the alpha or beta diversities of the microbial communities between muscles. The results indicated that PM has less color stability and a greater amount of microbial growth than LL during retail display. Despite the increased number of bacteria on PM earlier during display, the microbiome analyses showed no major differences in the microbial communities between the muscles on the same display day. These data may suggest that microbial metabolic pathways, evidenced by faster microbial growth on PM compared to LL, may be a bigger contributor to color stability differences than the microbial community composition. Further work establishing these metabolic differences is needed to understand the biochemical interaction between the microbiota and the beef steaks.Item Open Access Nutritional composition and food safety interventions of plant and animal-sourced foods(Colorado State University. Libraries, 2021) Swing, Caleb John, author; Nair, Mahesh Narayanan, advisor; Geornaras, Ifigenia, committee member; Weir, Tiffany L., committee member; Belk, Keith E., committee memberNutritional composition of plant- and animal-sourced food is important for human growth and development, and yet even nutritious food-groups can be detrimental to human health if contaminated with harmful pathogens upon consumption. Therefore, two studies were performed to assess the nutritive quality of plant- and animal-sourced proteins; as well as, the antimicrobial efficacy of novel sanitizers against a foodborne pathogen attributed to illness from plant- and animal-sourced food consumption. In the first study, nutrient profiles of animal-derived meat products, which are traditionally an important source of nutrients in the human diet, were compared to novel plant-based meat alternatives, which have been growing in popularity among modern consumers. Nutritional composition of two different formulations of the Beyond Meat Burger (BMB1 and BMB2), Impossible Food Burger (IFB1 and IFB2), 80/20 ground pork (GP), and 80/20 ground beef (GB) were analyzed for proximate, mineral, vitamin, fatty acid, and amino acid profiles. Crude protein and crude fat content did not differ (P > 0.05) for each product in cooked states. Plant-based meat alternatives were either numerically greater than or did not differ statistically (P < 0.05) from animal-derived meat products in every mineral tested. Fat soluble vitamin A, D2, D3, and K1 were below detection limits (< 0.3 mcg/g for vitamin A; < 0.001 mcg/g for vitamin A, D2, D3, and K1) in all raw and cooked samples. Vitamin E content in raw and cooked plant-based meat alternatives was substantially greater (P < 0.05) than in raw and cooked animal-derived meat products. Raw and cooked GP and GB were substantially greater (P < 0.05) than IFB1 and IFB2 in pantothenic acid (B5) but otherwise were numerically similar to or statistically less (P < 0.05) than IFB1 and IFB2 in most B vitamins tested. Total saturated and monounsaturated fatty acids did not differ (P > 0.05) for BMB2, IFB2, GP, and GB. IFB1 and IFB2 were greater (P < 0.05) than GP and GB in oleic acid (C18:1) content. Fatty acid profiles of raw and cooked BMB2 and IFB2 did not differ (P > 0.05) from one another. Essential amino acid composition of raw and cooked plant-based meat alternatives and animal-derived meat products were numerically comparable. Raw BMB2 did not differ (P < 0.05) from raw GP in histidine, lysine, and threonine content and was otherwise greater (P < 0.05) than raw GP in tyrosine, isoleucine, leucine, and valine. Raw GP was only numerically greater (P > 0.05) than raw BMB2 in methionine and tryptophan. In conclusion, plant-based meat alternatives assessed in this study were comparable to animal-derived GP and GB in most nutrient profiles assessed, providing high values of minerals, vitamins, fatty acids, and amino acids. Nonetheless, the high concentrations of certain nutrients as well as the integration of these nutrients into a food matrix may have implications for bioavailability and must be further investigated. In the second study, efficacy of novel antimicrobial sanitizers was assessed in relation to reducing Listeria monocytogenes contamination on a plant-based food. Both plant and animal-sourced foods have proven to be vectors of L. monocytogenes contamination, but a largescale, multistate listeriosis outbreak was attributed to whole cantaloupes raising concerns for the potential contamination of other fresh produce not previously associated with L. monocytogenes contamination. This study assessed efficacy of chlorine as well as different concentrations of novel sanitizer and sulfuric-acid based surfactant blends, peroxyacetic acid (PAA) and ProduceShield Plus (PSP), against inoculated L. monocytogenes populations on whole cantaloupe melons (Cucumis melo L. var. reticulatus). Cantaloupe melons (n = 6) were inoculated with a five strain mixture of L. monocytogenes (7 - 8 log CFU/cantaloupe) and immersed in water, chlorine (40 ppm), PSP (pH 1.81), PAA (40, 80, 250 ppm), or PAA+PSP (40, 80, 250 ppm and PSP blend) sanitizer solutions, under slight agitation for 0.5, 1, and 5 min exposure times. Recovery of surviving L. monocytogenes populations after immersion treatment, was accomplished by vigorously shaking whole cantaloupes in D/E neutralizing broth and plating the rinsates on PALCAM agar. The L. monocytogenes inoculation level achieved on whole cantaloupes was 7.9 ± 0.4 log CFU/cantaloupe. Immersion of inoculated whole cantaloupes in water or PSP achieved pathogen reductions that ranged between 0.3 to 0.5 log CFU/cantaloupe, and 0.9 to 1.8 log CFU/cantaloupe, respectively, across the three different exposure times (0.5, 1, 5 min). Reductions of L. monocytogenes populations on inoculated cantaloupes treated with 40 ppm chlorine achieved less than or equal to 3.3 log CFU/cantaloupe reductions across the different exposure times; while different concentrations of PAA (40, 80, 250 ppm) all achieved greater than or equal to 3.1 log CFU/cantaloupe reductions across the three exposure times. Different concentrations of PAA (40, 80, 250 ppm) blended with PSP resulted in pathogen reductions of between 3. 2 and > 4.9 log CFU/cantaloupe across the different exposure times. Decontamination efficacy of each PAA concentration level, within each treatment and exposure time, was similar (P > 0.05) to that of its corresponding PAA+PSP blend for most cases, although the PAA+PSP blends had numerically greater reductions than each corresponding PAA treatment and contained several samples which were below the detection limit of (2.7 log CFU/cantaloupe). In summary, PAA and the PAA+PSP blends demonstrated the greatest antimicrobial efficacy against L. monocytogenes populations on inoculated whole cantaloupes. More research should be conducted to elucidate a possible synergistic effect between PAA and sulfuric acid-based surfactants, such as PSP, on plant and animal-sourced foods susceptible to L. monocytogenes contamination.Item Open Access Quality and nutritional aspects of conventional and novel food proteins(Colorado State University. Libraries, 2020) Thompson, Tyler Warren, author; Nair, Mahesh Narayanan, advisor; Belk, Keith E., advisor; Geornaras, Ifigenia, committee member; Weir, Tiffany, committee memberCattle weights have increased during the last couple of decades and have not always been accompanied by improvements in facility capabilities and management. Alongside quality issues of color, tenderness, and water holding capacity, issues such as sour muscles and bone taints are now appearing with high frequency in the meat industry. Development of off-flavor/sourness in deep muscles such as knuckles (vastus femoris, vastus lateralis, vastus medialis, and rectus femoris) has been a long-standing issue in the beef industry, however, has not been well characterized. Therefore, the objective of this study was to investigate the potential cause and to characterize the sour odor associated with beef knuckles using microbial, odor panel, and gas chromatography-mass spectrometric (GC-MS) analyses. Knuckles (n = 10) identified as having no sour odor (control), slight sour odor (SLI-SO), or severe sour odor (SVR-SO) were collected from the fabrication line of a commercial beef processing plant. Upon collection of knuckles, synovial fluid and the femur surface were swabbed to determine psychrotrophic anaerobic sporeformer presence. The collected knuckles were transported on ice to the laboratory where they were aseptically separated into two halves, with one half destined for microbial, odor, and GC-MS analyses on the day of collection (day 0) and the other half for the same analyses (excluding GC-MS) after 35 days of vacuum packaged storage at 0 - 2°C (day 35). For microbial analysis, 15 g of tissue was excised from the muscle surface and was analyzed for aerobic plate counts (Petrifilm Aerobic Count plates) and lactic acid bacteria counts (Lactobacilli MRS agar). Samples (5 g) for GC-MS were held at -80°C until analysis. The remainder of the sample was diced and used for trained odor panels. Odor panelists identified differences (P < 0.05) for all tested attributes (off odor, oxidation, putrid, and sour notes) between control and sour knuckles (SLI-SO and SVR-SO) on day 0. Similarly, on day 35, differences (P < 0.05) were observed between control, SLI-SO, and SVR-SO knuckles for all attributes, with SVR-SO samples receiving the highest score for all categories. However, the microbiological analysis found no differences between aerobic plate counts and lactic acid bacteria counts of control, SLI-SO, and SVR-SO knuckles on day 0 or day 35. In addition, GC-MS analysis did not indicate a difference (P > 0.05) in the abundance of volatiles between the treatments (probably due to high variations within treatment groups). Overall, compounds such as acetic, acetoin, propionic, butyric, and isobutyric acid were trending towards having greater abundance in sour samples. Although animal proteins have been the primary source of protein in the human diet, plant-based proteins have gained popularity in recent years. While some studies have indicated lesser environmental impacts, the nutritional composition of plant-proteins has not been readily investigated. Therefore, the objectives were to evaluate the nutritional composition of Morning Star Farms spicy black bean burger (VB), Beyond Meat's Beyond Burger (BB), Impossible Food's Impossible Burger (IB), a boneless top loin pork chop (PC), and 80% lean 20% fat ground pork (GP). Six different cities were selected for product collection to give a representative view of the products (Seattle, WA; Peyton, CO; Memphis, TN; Newburgh, IN; Houston, TX; and Brooklyn, NY). Following collection, products were brought back to Colorado State University. Half of the products sampled from each city were cooked, and the remaining half were left in their raw state. All ground products were cooked to an internal temperature of 71°C while the PC was cooked to 63°C. Samples (both raw and cooked) were then homogenized individually and stored under vacuum-packaged conditions at -80°C until further analysis. Methodologies for proximate analysis, amino acids, fatty acids, minerals, vitamins, organic acids, and allergens were conducted following the Association of Official Analytical Chemist (AOAC) guidelines. Overall, the product state (raw or cooked) had little effect on the nutritional composition. Analysis indicated that the PC contained the highest (P < 0.05) amounts of protein, essential amino acids, and B-vitamins. Cholesterol was found highest (P < 0.05) in the pork products (PC and GP) with no cholesterol being identified in the plant-based products (VB, BB, and IB). However, when evaluating mineral make-up, the plant-based products contained the highest (P < 0.05) amounts, especially in sodium and iron levels. Sodium levels were about ten times higher, along with iron levels being 3 to 4 times higher in plant-based products. Overall, the pork products were found to contain the greatest amounts of amino acids, and B-vitamins needed in a diet. While the plant-based products were generally lower in nutrients, the IB was found at nutritional levels close to the GP and PC.Item Open Access Ractopamine withdrawal, depletion, and residue testing in beef cattle(Colorado State University. Libraries, 2019) Davis, Haley E., author; Belk, Keith E., advisor; Engle, Terry, committee member; Geornaras, Ifigenia, committee member; Prenni, Jessica, committee member; Yang, Hua, committee memberStudies were conducted to evaluate use of ractopamine hydrochloride (RH) in beef cattle production and the effect of various withdrawal times and depletion periods on residues in tissues and fluids collected from live and harvested animals. Primary objectives of these studies were: i) to develop and validate a LC-MS/MS assay to determine if detectable and quantifiable levels of RH can be detected in digestive tract-derived edible offal items of cattle resulted from tissue residues or residual ingesta contamination; ii) to determine presence of ractopamine in tissues after 12 h, 2, 4, and 7 days of withdrawal (in comparison to negative control cattle which did not receive RH); iii) to develop U.S. beef industry best practices for RH use for export to the Chinese market; and iv) to test the impact of withdrawal from ractopamine hydrochloride in the diets of feedlot cattle for 2, 4, or 7 days on residues for parent and total ractopamine in muscle, fat, rendered tallow, and large intestines in contrast to a true negative control group as well as validate and test feed samples to verify ractopamine presence using LC-MS/MS protocols. In the first study, tissue samples and corresponding rinsates from 10 animals were analyzed for parent and total ractopamine (tissue samples only). The lower limit of quantitation was between 0.03 - 0.66 ppb depending on tissue type, and all tissue and rinsate samples tested had quantifiable concentrations of ractopamine. The greatest concentration of tissue specific ractopamine metabolism (represented by higher total vs. parent ractopamine levels) were observed in liver and small intestine. Contamination from residual ingesta (represented by detectable ractopamine in rinsate samples) only was detected in small intestine, with a measured mean concentration of 19.7 ppb (+/- 12.2 ppb). Taken together, these results underscored the importance of the production process and suggested that improvements may be needed to reduce likelihood of contamination from residual ractopamine in digestive tract-derived edible offal tissues for market. In the second study, liver and muscle samples were collected after 2, 4, and 7 days of withdrawal from RH due to regulatory issues surrounding 12-h samples. Parent and total ractopamine residues in individual liver samples ranged from a minimum of 3.40 and 3.46 ppb, respectively, for the control treatment group, to a maximum of 3.54 and 14.19 ppb, respectively, for the 2-day withdrawal treatment group. For the individual muscle samples, parent and total ractopamine concentrations ranged from below the limit of quantification (0.12 ppb) in the control samples, to 1.13 (parent ractopamine) and 1.72 ppb (total ractopamine) in 2-day withdrawal samples. Therefore, overall, parent and total ractopamine concentrations detected in the liver and muscle samples fell far below the MRL set by Codex and FDA. The greatest parent and total ractopamine levels (282.40 and 289.85 ppb, respectively) were detected after 12 h withdrawal in individual large intestine samples, followed by small intestine (142.26 and 181.91 ppb, respectively) and omasum (109.70 and 116.90 ppb, respectively) samples. Because detectable levels of ractopamine were identified in tissues collected from control animals (i.e., animals not receiving RH in their ration), further research was conducted to determine potential sources of ractopamine contamination, and frequency and accuracy of testing in global markets. For example, eight feed-grade tallow samples were analyzed for parent and total ractopamine presence as a potential source of contamination, especially in cattle not receiving ractopamine in their rations. Ractopamine concentrations of 0.40 to 50.80 ppb were obtained for these tallow samples. While this could potentially explain the detectable levels of ractopamine residues found in control samples and the fact that 7-day withdrawal did not result in non-detectable levels, further research looking at tallow recycling and residual proteins in tallow is necessary to understand the implications of contaminated tallow on residue levels across tissues. Data from the current study may be useful in developing new recommendations for RH use and withdrawal to beef cattle producers in the U.S. who intend to export to global markets. Results from the third study revealed several items of interest, for example; RH declines rapidly in the lower GI of beef cattle, with levels below detection by day four. Additionally, there is a very small likelihood of RH cross-contamination via tallow inclusion in diets. Finally, the fourth study indicated that RH residues can, in fact, be quite low; however, because of limits of detection which are above zero, it is nearly impossible to quantify a level as 0.00 ppb, making zero tolerance requirements insurmountable. Overall, results of these studies were promising in that they showed that RH levels were lower than once thought, but there is a long way to go before zero-tolerance requirements can be met.Item Open Access Salmonella contamination in poultry – are we missing a potential reservoir?(Colorado State University. Libraries, 2017) Sexton, Ty L., author; Martin, Jennifer N., advisor; Geornaras, Ifigenia, committee member; Belk, Keith E., committee member; Bunning, Marisa, committee memberThe objective of this study was to assess presence and characteristics of Salmonella enterica found in synovial fluid of broiler carcasses. Synovial fluid of three individual joints from 500 broiler carcasses was individually sampled (1,500 total samples) from five broiler processing facilities located in the Southeast and Western U.S. The external surface of broiler carcass was decontaminated prior to sampling of the shoulder, coxofemoral, and tibiofemoral joints. Individual samples were enriched, composited, and subjected to rapid PCR-based detection of Salmonella. Individual samples from any positive composites were also enriched before determination of Salmonella presence in the same manner. Positive individual samples were subjected to secondary enrichment before plating onto selective agar for isolation of Salmonella. Salmonella isolates were serotyped before determination of antimicrobial susceptibility. Overall, 1.00% (5 out of the 500 broiler carcasses) of composite samples, and 0.47% (7 out of 1,500 samples) of individual samples were positive for Salmonella. Five of the seven isolates were susceptible to all drugs and determined to be Salmonella Enteritidis. The remaining two isolates, identified as Salmonella Typhimurium, were resistant to streptomycin. To our knowledge, no previous assessments of Salmonella in synovial fluid of broilers has been reported; however, results of the present study suggested that Salmonella may be present in synovial fluid of broilers. Although low prevalence, this information provides valuable insight into potential poultry contamination pathways and warrants further exploration.Item Open Access The survival of inoculated populations of Listeria monocytogenes and Staphylococcus aureus on shelf-stable meat bars during vacuum-packaged storage(Colorado State University. Libraries, 2018) Bullard, Brittney Rose, author; Delmore, Robert J., advisor; Belk, Keith E., committee member; Geornaras, Ifigenia, committee member; Martin, Jennifer N., committee member; Weir, Tiffany L., committee memberTo view the abstract, please see the full text of the document.Item Open Access Trace mineral source impacts rumen trace mineral distribution and fiber digestion in steers fed a low-quality forage-based diet(Colorado State University. Libraries, 2020) Guimaraes, Octavio, author; Engle, Terry, advisor; Geornaras, Ifigenia, committee member; Holt, Timothy, committee memberTwelve Angus steers (BW 452.8 ± 21.8 kg) fitted with ruminal cannulae were used to determine the impact of trace mineral (TM) source on neutral detergent fiber (NDF) digestibility, short chain fatty acid (SCFA) production, ruminal solubility of Cu, Zn, and Mn, and relative binding strength of trace minerals located in the rumen insoluble digesta fraction. Steers were fed a low-quality grass hay diet (DM basis: 10.8% CP, 63.1% NDF, 6.9 mg Cu/kg, 65.5 mg Mn/kg, and 39.4 mg Zn/kg) supplemented with protein for 21 d. Treatments consisted of 20, 40, and 60 mg supplemental Cu, Mn, and Zn/kg DM, respectively, from either sulfate (STM) or hydroxy (HTM) sources (n=6 steers/treatment). Following a 21-d adaptation period, total fecal output was collected for 5 d. Dry matter digestibility tended (P < 0.07) to be reduced (51.9 vs. 53.4 ± 0.52%) and NDF digestibility was reduced (P < 0.04; 40.4 vs. 42.7 ± 0.67%) in STM vs. HTM supplemented steers. On d-6, rumen fluid was collected at 0, 2, and 4 h post feeding and analyzed for SCFA. There were no treatment x time interactions for any response variables measured. However, treatment was a significant (P < 0.05) source of variation for butyric acid and total SCFA production. Steers receiving HTM had less (P < 0.02) butyric acid and greater (P < 0.05) total SCFA than STM supplemented steers. Steers were then fed the same low-quality grass hay diet without supplemental Cu, Zn, or Mn for 14 d. On d-15, steers received a pulse dose of 20 mg Cu, 40 mg Mn, and 60 mg Zn/kg DM from either STM or HTM sources (n=6 steers/treatment). Ruminal samples were obtained at 2-h intervals starting at -4 h and ending at 24 h relative to dosing. There was a treatment x time interaction for ruminal soluble Cu, Mn and Zn concentrations. Ruminal soluble mineral concentrations were greater (P < 0.05) for Cu at 4, 6, 8, 10, 12, and 14 h; for Mn at 4 and 6 h; and for Zn at 4, 6, and 8 h post dosing in STM compared to HTM supplemented steers. Concentrations of Cu and Zn in ruminal solid digesta were also affected by treatment, time, and treatment x time. At 12 h post dosing, Cu and Zn concentrations were greater (P < 0.05) in HTM supplemented steers when compared to STM supplemented steers. Upon dialysis against Tris-EDTA the % Zn released was greater at 12 h (P < 0.03) and 24 h (P < 0.05) and the % Cu released was greater (P < 0.02) at 24 h post dosing when compared to STM supplemented steers. Results indicate that Cu and Zn from HTM have low solubility in the rumen, may improve fiber digestibility and appear to be less tightly bound to ruminal solid digesta than Cu and Zn from STM.