Theses and Dissertations

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Open Access
Genetic relationships between sex-specific traits in a crossbred beef cattle population
(Colorado State University. Libraries, 1993) Speer, Nevil, C., author; Brinks, James S., advisor
Data used were obtained from the Fort Keogh Livestock and Range Research Laboratory (LARRL), Miles City, Montana. Data were from a crossbreeding experiment involving Hereford, Angus and Charolais cattle collected from 1962 to 1977. Traits studied and considered separate with respect to sex, included male and female birth weight (BWM and BWF), weaning weight (WWM and WWF), and postweaning average daily gain (ADGM and ADGF). Other traits studied were average adjusted mature weight (MW) of cows and fat thickness (FT), ribeye area (REA), yield grade (YG), quality grade (QG) and days on feed (DOF) of bulls and steers slaughtered at a weight constant endpoint of 1000 - 1050 lb. Multi-trait sire-maternal grandsire REML analyses were performed on straightbred and crossbred Hereford, Angus, and Charolais cattle. Observations on 2888 animals contributed to development of the A-inverse which represented relationships among 138 sires and maternal grandsires. Models for BWM, BWF, WWM, WWF, ADGM, ADGF, and MW analyses models included birth year, age of dam (2, 3, 4, 5+) and linear regression on weaning age. The DOF analysis model included birth year, age of dam, sex of calf (bull vs steer), age of dam-sex of calf interaction and linear regression on weaning age. Carcass trait (FT, REA, YG, QG) models included birth year, age of dam, sex of calf, age of dam-sex of calf interaction and linear regression on carcass weight. Linear regressions on individual breed percentage, combined reciprocal cross percentage (individual heterosis), dam breed percentage and dam combined reciprocal cross percentage (maternal heterosis) were also included in all models for analyses of all traits of interest. Correlations between direct components of birth weight, weaning weight, and postweaning average daily gain considered separately between male and female calves were .93, .90 and .74 respectively. The correlation between direct components of MW and DOF was -.66. Correlations between direct components of MW and carcass traits were -.54, -.18, -.18, and .41 for FT, REA, YG and QG, respectively. Correlations between maternal components of birth weight, weaning weight, and postweaning average daily gain considered separately between male and female calves were .86, .98 and .42, respectively. The correlation between maternal components of MW and DOF was -.71. Correlations between maternal components of MW and carcass traits were .40, .10, .08, and -.06 for FT, REA, YG and QG, respectively. Correlations between mat-dir and dir-mat of the same traits studied were moderate and ranged from -.44 to .47. Predictions of correlated responses in mature weight per standard deviation of direct response in male carcass traits were -32 lb, -13 lb, -10 lb, and 31 lb respectively for FT, REA, YG and QG. Correlated response predictions indicate selection for improved carcass cutability on a weight constant basis (increased leanness and decreased yield grades) would increase mature weight while selection for increased ribeye area and decreased quality grade scores (favorable) on a weight constant basis would result in decreased mature weights of females. Strong selection pressure for leanness may be antagonistic to commercial beef producers since results suggest sires selected on the basis of reducing fat in steer progeny also produce females that are larger at maturity when cattle are slaughtered at a constant weight endpoint. It should be noted, however, relationships between carcass traits and mature weight may differ when cattle are slaughtered at a constant age endpoint.
Open Access
The effects of marginal zinc deficiency on biochemical and physiological parameters in beef heifer and holstein steer calves
(Colorado State University. Libraries, 1996) Engle, Terry E., author; Nockels, Cheryl F., advisor; Kimberling, Cleon, committee member; Ward, Gerald M., committee member
To view the abstract, please see the full text of the document.
Open Access
Effects of antimicrobials in the formulation and post-packaging thermal treatment to control Listeria monocytogenes in post-processing inoculated frankfurters
(Colorado State University. Libraries, 2001) Bedie, Gerard Kouadio, author; Sofos, John N., advisor; Schmidt, Glenn R., committee member; Sampson, David A., committee member
Listeria monocytogenes presents a major food safety concern due to its ability to survive or grow at refrigeration temperatures (4°C) and in other adverse conditions (salt, heat, low pH, and large temperature range). Since L. monocytogenes transmission, in the case of human outbreaks, is generally associated with post-processing contamination of ready-to-eat foods, actions to eliminate or reduce the pathogen's occurrence in foods should be applied during processing and post-processing. The objectives of these studies were to determine the effectiveness of certain antimicrobials (i.e., sodium lactate at 3% or 6%, sodium diacetate at 0.25% or 0.50%, sodium acetate at 0.25% or 0.50%, nisin as Nisaplin® at 0.15%, lysozyme at 0.01 %, monolaurin at 0.01 %, glucono-delta-lactone at 0.25%, and allyl isothiocyanate at 0.02%, in the first study-Chapter III) or their combinations (i.e., sodium lactate at 3% with sodium acetate at 0.25%, sodium lactate at 3% with sodium diacetate at 0.25%, or sodium lactate at 3% with glucono-delta-lactone at 0.25%, in the second study-Chapter IV) included in the formulation of frankfurters against L. monocytogenes inoculated on their surface after peeling and before vacuum packaging, as well as the antimicrobial effect of thermal treatment (i.e., dipping in hot water of 7 5-80°C for 30-90 sec; in the second study-Chapter IV). Samples were stored (for 50 or 120 days) at 4°C and periodically analyzed for microbial growth (TSA YE and PALCAM agar), pH, moisture, fat, and water activity. In the first experiment of the first study (Chapter III), growth of L. mo11ocytogenes reached I 08 cfu/cm2 in the frankfurters containing no antimicrobials during storage. Sodium lactate at 6% and sodium diacetate at 0.50% incorporated in the formulation of frankfurters singly, inhibited growth of L. monocytogenes stored at 4°C for 120 days. Sodium lactate at 3% inhibited growth of the pathogen for 50 days, while nisin at 0.15% added in the formulation of the frankfurters, in the second experiment, inhibited growth of the organism for 10 days. Under the conditions of the second experiment in the first study (Chapter III), other antimicrobials used singly in the product did not affect growth of L. monocytogenes during storage. The water activity of products containing sodium acetate (0.25 or 0.50%) and sodium diacetate (0.25 or 0.50%) was slightly below that of the control (0.972) while sodium lactate decreased remarkably the water activity of the product as its concentration increased from 3% to 6% reaching, respectively, 0.946 and 0.933. Nisin (0.15%), allyl isothiocyanate (0.02)%, lysozyme (0.01)%, monolaurin (0.01)%, and glucono-delta-lactone (0.25%) did not affect the water activity of the product. None of the individual antimicrobials added in the formulation affected the cooking yield, or the moisture and fat contents of the products. On day 0, pH of the products containing sodium diacetate (0.25 or 0.50%) decreased to 6.03 and 5.87, respectively, compared to that of the inoculated control (6.31). However, pH of the inoculated control decreased dramatically to reach 5.42 during storage as growth of the pathogen reached higher levels (107-108 cfu/cm2). Combinations of sodium lactate (3%) with sodium acetate (0.25%), sodium diacetate (0.25%), or glucono-delta-lactone (0.25%) inhibited growth of L. monocytogenes for 120 days on frankfurters stored at 4°C, while growth of L. monocytogenes on the inoculated control frankfurters reached l 07 cfu/cm2 in 35 days. When thermal treatment and antimicrobial combinations were applied to the frankfurters (Chapter IV), inhibition of L. monocytogenes was enhanced. Thermal treatment used alone on the vacuum packaged frankfurters inhibited growth of the pathogen for 35 days when one frankfurter per bag was dipped in hot (75 or 80°C) water for 90 sec. While the water activity and the cooking yield were not affected by the combination of antimicrobials in the products, sodium lactate (3%) combined with sodium diacetate (0.25%) decreased slightly the moisture while the fat content increased by approximatively 3%. The combination of sodium lactate (3%) with sodium diacetate (0.25%) or glucono-delta-lactone (0.25%) decreased the pH of the frankfurters. Moreover, the pH in the inoculated control decreased dramatically after 35 days of storage at 4°C and reached, at the end of the storage, 5.30 for the non-dipped frankfurters and 5.58 when they were dipped in hot water (80°C). The pH of frankfurters with no antimicrobials but dipped in hot (75-80°C) water dropped remarkably after 35 days in all treatments as a consequence of the high level of microbial growth on the product. In addition, the microbial counts on TSA YE agar were higher than those on P ALCAM agar in all treatments during storage. These results indicate that use of combinations of permissible levels of antimicrobials in the formulation exhibited an antimicrobial activity in cooked meat products stored at 4°C for 120 days. In addition, thermal treatment may enhance the inhibitory activity of the antimicrobials during storage.
Open Access
Effects of copper source and concentration on copper status and immune function in growing and finishing steers
(Colorado State University. Libraries, 2002) Dorton, Kristy L., author; Engle, Terry E., advisor; Hamar, Dwayne W., committee member; Siciliano, Paul D., committee member
Forty-eight, individually fed, purebred Angus steers (approximately 7 months of age, 218 + 9.1 kg) were used to determine the effects of copper (Cu) source and concentration on performance, Cu status, and immune function. Steers were stratified by weight and initial liver Cu concentration and randomly assigned to one of five treatments. Treatments consisted of: 1) control (no supplemental Cu), 2) 10 mg Cu/kg DM from Cu sulfate (CuS04), 3) 10 mg Cu/kg DM from a Cu-amino acid complex (Availa Cu), 4) 20 mg Cu/kg DM from CuS04, and 5) 20 mg Cu/kg DM from Availa Cu. Steers were housed in individual pens and fed an alfalfa-com based growing diet for 56 d then were fed a high concentrate diet for 144 d. On d 56 of the growing phase and d 112 of the finishing phase, liver Cu concentrations were higher (P < 0.01) in Cu supplemented steers. Steers receiving 20 mg Cu/kg DM had higher (P < 0.01) liver Cu concentrations than steers receiving 10 mg Cu/kg DM. On d 112 of the finishing phase, steers receiving 20 mg Cu/kg DM from Availa Cu had higher (P < 0.01) liver copper concentrations than steers supplemented 20 mg Cu/kg DM from CuS04. In the growing phase, steers supplemented with 20 mg Cu/kg DM had greater (P < 0.04) plasma Cu concentrations than steers supplemented with 10 mg Cu/kg DM. In the growing and finishing phases, plasma Cu concentrations were higher (P < 0.03) in steers supplemented with 20 mg Cu/kg DM from Availa Cu than steers receiving 20 mg Cu/kg DM from CuS04. Cell mediated immune response to phytohemagglutinin was higher (P < 0.01) in steers supplemented with 20 mg Cu/kg DM than 10 mg Cu/kg DM treatments. Total immunoglobulin (lg) and immunoglobulin G (IgG) concentrations specific to pig red blood cells (PRBC) were greater (P < 0.01) in steers supplemented with 10 mg Cu/kg DM from CuS04 than 10 mg Cu/kg DM from Availa Cu. During the finishing phase, IgG concentrations specific to PRBC were higher (P < 0.03) and antibody titers specific to ovalbumin (OVA) were lower (P < 0.05) in control steers relative to Cu supplemented steers. Steers receiving 20 mg Cu/kg DM had higher antibody titers specific to OVA (P < 0.02) than 10 mg Cu/kg DM steers. Steers receiving 20 mg Cu/kg DM from Availa Cu had higher (P < 0.01) antibody titers specific to OVA than steers supplemented with 20 mg Cu/kg DM from CuS04 . These results indicate that Cu source and concentration may have an effect on the immune system. Furthermore, it appears that the immune response to an antigen varies depending on the type of antigen administered as well as the concentration and source of Cu supplemented.
Open Access
Copper, zinc, and manganese in beef cattle production: effects of supplementation and source on reproduction, mineral status, feedlot performance, immunity, and carcass characteristics
(Colorado State University. Libraries, 2004) Ahola, Jason K., author; Engle, Terry E., advisor; Burns, Patrick D., advisor; Seidel, George E., committee member; Whittier, Jack C., committee member; Field, Thomas G., committee member
Over a two-year period, crossbred mature beef cows ( n = 178, Year 1; n = 148, Year 2) and young females (n = 43 nulliparous heifers, Year 1; n = 37 primiparous cows, Year 2) grazing in eastern Colorado were used to evaluate the effects of Cu, Zn, and Mn supplementation and source on reproduction, mineral status, immunity, and cow and calf performance. Cow treatments included: 1) control (no supplemental Cu, Zn, or Mn); 2) organic (50% organic and 50% inorganic Cu, Zn, and Mn); and 3) inorganic (100% inorganic CuSO4, ZnSO4, and MnSO4) trace minerals. Heifer treatments included: 1) organic, or 2) inorganic trace minerals. Free-choice mineral feeders were used to provide current NRC-recommended concentrations of Cu, Zn, and Mn from 54 and 82 d (Year 1, heifers and cows, respectively) and 81 d (Year 2) prior to the average calving date of the herd through 110 and 119 d (Year 1, cows and heifers, respectively) and 135 d (Year 2) post-calving. Terminal steer and heifer calves from each year's calf crop were maintained on their appropriate pasture trace mineral treatments and had exclusive access to mineral treatments via creep feeders from approximately 95 d of age until weaning. After weaning, calves were grown and finished in a feedlot on the same pre-weaning trace mineral treatments. Performance, immune response, mortality, morbidity, mineral status, carcass traits, and longissimus dorsi fatty acid profiles were evaluated. In the grazing portion of the experiment, results indicate that trace mineral supplementation in cows and source in cows and heifers affected trace mineral status. Reproductive results were variable in heifers; however, in cows trace mineral supplementation improved pregnancy rate to AI compared to cows not supplemented with Cu, Zn, or Mn for more than 1 yr. Calf performance was greater in non-supplemented control calves vs. supplemented calves in both years, while source also affected calf performance but not consistently in both years. Trace mineral source did not affect calf performance in young grazing females. During the feedlot phase in Year 1, gain to feed ratio was greater in Inorganic vs. Organic calves in both the growing and finishing phases and greater in non-supplemented control calves vs. supplemented calves only during the finishing phase; however, gain to feed ratios were not affected by either supplementation or source in Year 2. Liver Cu and Mn concentrations were affected by supplementation, however immune response, morbidity, carcass traits, and longissimus dorsi fatty acid profiles were not different across treatments. Based on the reduced reproductive performance in non-supplemented cows, as well as literature indicating that Cu affects luteinizing hormone (LH) release, the effect of Cu status, supplementation and source on pituitary responsiveness to gonadotropin releasing hormone (GnRH) were evaluated using 12 multiparous, non-pregnant, non-suckling, ovariectomized Angus cows. After receiving 5 mg Mo/kg diet and 0.3% S during a 216-d Cu depletion phase, nine cows were considered Cu deficient (liver Cu concentrations < 30 mg Cu/kg) and were stratified based on age, BW, BCS, and liver Cu concentration and randomly assigned to treatments. Treatments included: 1) control (deficient Cu status; no supplemental Cu), 2) organic (adequate Cu status; 100% organic Cu, 10 mg Cu/kg diet), and 3) inorganic (adequate Cu status; 100% inorganic CuSO4 , 10 mg Cu/kg diet). By d 77 of the 159-d repletion phase all supplemented cows had adequate liver Cu, and liver Cu concentrations were greater in supplemented cows vs. non-supplemented controls, and this was maintained throughout the repletion phase. Beginning on d 99, cows were catheterized every fifth day and blood samples were collected at 15 min. intervals for 1 h prior to, and 4 h after, GnRH administration at low (0, 3, and 9 ug; experiment one) and high doses (0, 27, and 81 ug; experiment two) and analyzed for LH concentration. Copper status, supplementation, and source had no effect on pituitary sensitivity to GnRH (based on basal, peak, and total LH released at varying GnRH doses) or pituitary stores of LH.
Open Access
Effects of trace mineral supplementation, trace mineral source, growth implants, and induced morbidity on performance, trace mineral status, immune function, carcass characteristics, and lipid metabolism in steers
(Colorado State University. Libraries, 2005) Dorton, Kristy L., author; Engle, Terry E., advisor; Johnson, Celina R., committee member; Hamar, Dwayne W., committee member; Siciliano, Paul, committee member
Steers were utilized to determine the effects of trace mineral (TM) supplementation and source, growth implants, and morbidity on performance, TM status, immune function, carcass characteristics, and lipid metabolism. In experiment 1, steers were backgrounded at their respective ranches for 30 d post weaning on one of the following treatments: 1) control (no supplemental TM), 2) inorganic TM, and 3) iso-amounts of organic TM. After the 30 d backgrounding period, steers were transported to the feedlot where half of the steers per treatment were implanted and the remaining half were not implanted. In experiment 2, the first group of steers was inoculated intranasally with IBRV four months prior to weaning. The second group was inoculated with IBRV on arrival to the feedlot and the third group was not inoculated with IBRV. Once at the feedlot, calves were sorted to treatments, which consisted of 1) organic TM and 2) iso-amounts of inorganic TM. During the backgrounding phase of experiment 1, calves supplemented with organic TM had a greater ADG and a lower incidence of morbidity than calves supplemented with inorganic TM. Steers supplemented with organic TM had greater concentration of total IgM during the growing phase and greater concentrations of antibody titer specific to ovalbumin than steers supplemented with inorganic TM. Steers that were implanted had a greater ADFI, REA, HCW, dressing percentage, and acetyl CoA carboxylase activity, and a lower KPH than non-implanted steers. In experiment 2, liver Mn and Zn concentrations were decreased in IBRV steers, whereas, Cu concentrations were unaffected. Inoculated steers had lower oleic acid (18:1 n-9) and monounsaturated fatty acids. Steers that were inoculated with IBRV prior to arrival at the feedlot had lower concentrations of myristic acid (14:0) and linoleic acid (18:2 n-6). Key Words: Steers, trace minerals, growth implants, induced morbidity, performance, immunity, carcass characteristics, lipid metabolism.
Open Access
Survey of husbandry, management, housing, leg lesions, hygiene, production, economics, and cow behavior, on 113 commercial U.S. dairies
(Colorado State University. Libraries, 2007) Fulwider, Wendy K., author; Grandin, Temple, advisor
Dairy cattle should be kept clean, dry and comfortable. There are economic and welfare advantages for providing housing for dairy cows during the winter months instead of leaving them outside in harsh climates. To improve overall health and well-being, cows should be moved from indoor stalls into the barnyard, where they can groom themselves and one another. Cows should be able to stretch, sun themselves, exhibit estrus behavior, and exercise. To decrease the incidence of leg problems, mastitis, bloat, and calving-related disorders cows should be allowed generous access to outdoor pastures or exercise yards. In the first essay, dairy cow behavior, needs, and preferences for housing and milking centers is discussed. Current recommendations for stall size and management practices are reviewed. The social needs of dairy cattle and the benefits of positive human-animal interactions were reported. Recommendations for transport were also included. In the second essay, dairy cow hygiene, leg lesion incidence and location for cows on 113 dairies were recorded and analyzed. Stall bed types reviewed included compost pack, rubber filled mattresses, sand, and waterbeds. Results indicated that stall bed type was a good predictor for leg lesion incidence and location of wound, as well as level of hygiene. The numbers of mature cows present on a dairy were also related to bed type, as well as bed length in sand stalls. Severe lesions were associated with higher somatic cell counts. There were correlations between high somatic cell counts and the percentage of cows reported lame by the producer and the neck rail height. High leg lesion rates were correlated with somatic cell count, death loss, and percentage of herd reported lame. The third essay evaluates diiferent stall bed types for culling rate, percentage of mature cows in herd, bedding cost and frequency. Producer satisfaction for cow comfort, manure management, and cow longevity, by base type were reported. This data indicated that waterbeds were a viable option for cows and producers when good quality sand is unavailable or handling sand-laden manure is not feasible.
Open Access
Fate of Listeria monocytogenes on ready-to-eat meat products, treated with antimicrobials, and under conditions simulating passage through the human stomach and small intestine
(Colorado State University. Libraries, 2008) Barmpalia-Davis, Ioanna Maria, author; Sofos, John, advisor
To cause infection, the foodborne pathogen Listeria monocytogenes must overcome stresses associated with food processing, storage, and preparation, as well as various defense elements of the human body. In this work, we examined factors that may affect growth and survival properties of this pathogen on foods and during passage through a simulated stomach and small intestine.
Open Access
Effects of endocrine modifiers on growth, carcass characteristics, and blood and tissue metabolites of finishing beef cattle
(Colorado State University. Libraries, 2008) Bryant, Anthony C., author; Engle, Terry E., advisor
The effects of vitamin A and the interaction of steroids and beta-adrenergic agonists on growth and carcass performance, tissue metabolite profiles, and lipogenic enzyme activity were evaluated in beef cattle. In 1 experiment steers were fed 1 of 5 supplemental levels of vitamin A (0, 1,103, 2,205, 4,410, or 8,820 IU/kg DM). Final BW, G:F, ADG, HCW, LM area, marbling, and quality grade distribution did not differ among treatments. Except for d 56, no correlations between marbling score and tissue retinol concentrations or vitamin A intake were found. A negative correlation between liver retinol and α-tocopherol was observed, which may have potential health implications. Results suggest that vitamin A supplementation up to twice the NRC-suggested concentration has little effect on performance, marbling, or lipogenic enzyme activity in yearling steers and further suggest that 2,205 IU supplemental vitamin A/kg of DM is adequate for growing/finishing beef steers.
Open Access
Heifer pregnancy genetic prediction and simulation modeling techniques
(Colorado State University. Libraries, 2008) Comstock, Carlton R., author; Enns, R. Mark, advisor; Bourdon, Richard M., advisor
The Colorado Beef Cattle Production Model (CBCPM) was rewritten with an object oriented design and used to simulate heifer pregnancy data with varying levels of age at puberty (AAP), probability of conception (PCON), and length of breeding season. Five percent of the heifers were simulated infertile due to non-genetic causes. Simulated data were used to estimate heritability of heifer pregnancy and to obtain EBV using threshold models. The EBV were tested for accuracy of prediction of the simulated genetic fertility traits. Object oriented methods used illustrated the ability of these techniques and tools, such as Unified Modeling Language, at organizing complex processes in ways to reduce errors and code maintenance effort, and to facilitate collaboration among developers. Adoption of these tools will be critical to the advancement of systems models. Heritability of heifer pregnancy from 20,000 heifers with very early puberty in the first 25 d of the breeding season was .139, .107, and .143 for mean PCON of 60, 70, and 80%, respectively, close to the .10 input heritability of PCON. The higher estimates may be due to a few heifers having two opportunities to breed. With very late puberty and 80% mean PCON in a 25 d breeding season the heritability estimate of AAP was .337, lower than the simulated .40 heritability. The estimate was lower because there was not 100% conception, some heifers were infertile, and puberty was observed as a threshold trait. Heritability estimates of heifer pregnancy generally decreased as breeding season length increased, likely due to an increasing percent of open infertile heifers. The ability of the variance component estimation software to converge on an estimate decreased as the number of open, fertile heifers decreased. The most difficulty was with high PCON, early puberty, and long breeding seasons; only one out of 100 estimates converged at 340 d AAP, 80% PCON, and 120 d breeding season. Calculated accuracy for heifer pregnancy EBV for the sires of the heifers using prediction error variances from a linear model, with the binary pregnancy observations treated as continuous data, overestimated accuracy of the EBV with respect to the simulated traits in all cases. Calculated accuracy was insensitive to changes in frequency of heifer pregnancy observations. Accuracy calculated as the simple correlation of the EBV with each simulated fertility trait for the sires of the heifers was highest in most cases at the shortest breeding season. The correlation with AAP was essentially zero for early puberty, and strongest (-.775) at late puberty. As breeding season length increased the AAP correlation declined toward zero. The accuracy for PCON was less sensitive to changes in AAP and breeding season length, ranging from .146 to .753; the strongest correlations were with early puberty and low PCON.
Open Access
Effects of brining ingredients and antimicrobials on thermal inactivation of Escherichia coli O157:H7 in a meat model system and control of Listeria monocytogenes in frankfurters
(Colorado State University. Libraries, 2009) Byelashov, Oleksandr Anatolievich, author; Sofos, John N., advisor
Microbial food safety has been one of the most important challenges for the meat industry and regulatory agencies during the last two decades owing to outbreaks by pathogens such as Escherichia coli 0157:H7 and Listeria monocytogenes traced tocontaminated products, and associated with costly product recalls from the market. Among others, E. coli 0157:H7 infections have been associated with undercooked contaminated brine-injected meats. L. monocytogenes is of particular concern in ready-to-eat (RTE) meat and poultry products.
Open Access
Determination of antibiotic, ß-agonist, and non-steroidal anti-inflammatory drug residues in ground beef from USDA certified organic, natural, conventional, and market cow and bull sources
(Colorado State University. Libraries, 2009) Bowling, Mitchell Brett, author; Belk, Keith, advisor
In recent years, consumer demand for organic and "natural" products has increased, partly due to a perception that such products are healthier and contain fewer additives, including veterinary drugs and growth promotants. The study presented herein compared occurrence of veterinary drug residues in ground beef samples reflecting different livestock production classifications. We collected ground beef samples (N = 400) consisting of 90.0 ± 4.0% lean muscle tissue from a total of eight plants, two each reflecting production in the following categories: (1) USDA Certified Organic (n = 100); (2) USDA Process Verified Never Ever 3 (n =1 00); (3) conventionally raised fed beef (n = 100); and (4) ground beef derived from carcasses of market cows and bulls (n = 100). Liquid chromatography coupled with triple-quadrupole mass spectrometry (UPLC-MS) methods were developed for the following veterinary drugs: (1) Aminoglycosides (Gentamicin, Amikacin, and Neomycin); (2) ß-lactams (Penicillin, Ampicillin, and Desfuroylceftiofur); (3) Fluoroquinolones (Danofloxacin and Ciprofloxacin); (4) Macrolides (Erythromycin, Tylosin, and Tilmicosin); (5) Phenicols (Florfenicol); (6) Sulfonamides (Sulfamethazine and Sulfadimethoxine,); (7) Tetracyclines (Oxytetracycline, Chlortetracycline, and Tetracycline); (8) Streptogramins (Virginiamycin); (9) ß-agonists (Ractopamine and Zilpaterol); and (10) non-steroidal anti-inflammatory drugs (Flunixin and Phenylbutazone). Residues exceeding their respective US tolerance limit were found in six ground beef samples. Two USDA Certified Organic samples contained Ampicillin residues exceeding US tolerance limits. One USDA Process Verified Never Ever 3 sample contained a residue of Ractopamine exceeding US tolerance limits. One sample from the market cow and bull category contained a residue of Sulfadimethoxine that exceeded US tolerance limits, one contained a residue of Ampicillin that exceeded US tolerance limits, and one contained a residue of Phenylbutazone that exceeded US tolerance limits. Residues of Phenylbutazone exceeding US tolerance limits were also found in one sample from the conventional production category. Additionally, residues (below the US tolerance limit) of several classes of veterinary drugs were found in samples from the USDA Certified Organic and USDA Process Verified Never Ever 3 production categories, a finding that clearly demonstrates violation of zero-tolerance statutes set forth by the National Organic Program and USDA Process Verified Never Ever 3 marketing descriptors. In the USDA Certified Organic production category, residues were detected in eight Ampicillin, seven Penicillin, three Sulfamethazine, one Sulfadimethoxine, and one Ractopamine sample. In the USDA Process Verified Never Ever 3 production category, residues were detected in one Ampicillin, one Chlortetracycline, two Tetracycline, and six Ractopamine samples. These violations exceed the historical prevalence of veterinary drug residues reported by the National Residue Program and demonstrate the need for careful monitoring of animals administered veterinary drugs in order to prevent improper inclusion of unqualified animals in premium marketing programs, such as USDA Certified Organic and USDA Process Verified Never Ever 3 programs.
Open Access
Ecology and persistence of Escherichia coli O157:H7 in feedlot cattle and characterization of molecular mechanisms responsible for attachment
(Colorado State University. Libraries, 2009) Carlson, Brandon Adolph, author; Belk, Keith E., advisor
Studies were conducted to elucidate the shedding dynamics and ecology of Escherichia coli O157:H7 in feedlot cattle. Feedlot cattle (N=788) were evaluated for E. coli O157:H7 shedding six times during the final 120 d of finishing. Fecal samples were analyzed for E. coli O157:H7 with IMS and confirmed with multiplex PCR. During the first two collections, where all 788 steers were samples, 39.8 and 33.6% of steers were shedding an E. coli O157:H7 isolate possessing eae, stxI, and stxII. Through subsequent sampling, 1% of steers were characterized as persistent E. coli O157:H7 shedders (PS) where as 1.4% of steers were never shedding a detectable amount of the organism. Molecular characterization of E. coli O157:H7 isolates obtained from PS (n=80) and transient E. coli O157:H7 shedders (n=52) revealed a diverse but closely related population of isolates and identified a predominant subtype that accounted for 53% of the isolates characterized that was not dependent (P > 0.05) on animal shedding status. Pathogenic potential of E. coli O157:H7 isolates representing different subtypes was delineated with a Caco-2 cell (intestinal epithelial cell line) attachment assay. There was an inverse relationship (P < 0.05) between genetic diversity and attachment efficacy; as diversity from the dominant subtype increased, ability to attach to Caco-2 cells diminished. Additional attachment assays were initiated to evaluate the influence of virulence genes upon E. coli O157's ability to attach to Caco-2 cells. E. coli O157 isolates without either stx, no stxI, and no stxII genes resulted in attachment abilities of 76.7, 65.5 and 57.7%, respectively; all of which were greater (P < 0.05) than an E. coli O157:H7 that was isolated from a food implicated in human disease and possessed both stx genes. Cytotoxicity assays were utilized to verify that differences in attachment efficacy, exhibited by E. coli O157 isolates of various virulence genotypes, were independent of cellular destruction.
Open Access
Pre-harvest and postmortem methods of decreasing the incidence and salvaging value of non-conforming beef carcasses
(Colorado State University. Libraries, 2009) Bass, Phillip Dean, author; Belk, Keith, advisor; Scanga, John, advisor
It has been stated that the number of non-conforming carcasses in the beef industry cost the industry millions of dollars yearly in lost revenue. The objectives of this research were to identify muscles in dark-cutting beef carcasses that were not affected by the dark-cutting condition, identify relationships between the portion size of individual muscles in the beef carcass and the carcass ribeye area, and finally to investigate the effects of dietary magnesium (Mg) supplementation on the quality characteristics of beef cattle subjected to stress-inducing environments. Carcasses in the dark cutter study were divided into three classes; 1/3, 1/2, and full degree of dark cutting (DEGDC). The ultimate pH of individual muscles within the carcasses resulted in 7, 9, and 5 muscles having mean pH values considered normal for 1/3, 1/2, and full DEGDC carcasses, respectively. A nation wide survey was conducted to identify the acceptable color range of fresh beef muscles for food service chefs and retail meat merchandisers. Muscles that were within an acceptable color value range for food service chefs and retail meat merchandiser had the potential to add up to $42.29 and $30.30 per side when valued at Choice prices compared to commodity discounted prices, respectively. The portion size study evaluated 14 muscles. Seven of the 14 muscles were found to have no relationship between individual muscle portion size and ribeye area. A nationwide survey was conducted with foodservice chefs and retail meat merchandisers to evaluate the acceptability of portion sizes from carcasses varying in ribeye area size. Results of the survey demonstrated that the portion size of many muscles were still acceptable to retail meat merchandisers and foodservice chefs even though the ribeye area of a carcass may be non-conforming. The study involving the Mg supplementation to beef cattle (N = 144) indicated that the Mg was taken up in the blood stream of the cattle fed the supplement, but no effect on tenderness or reduction of quality defects (e.g., dark cutting) were observed. The results of these studies demonstrate methods of returning value to non-conforming beef carcasses, however, other methods of preventing non-conformity are necessary to research.
Open Access
Prevalence and control of Listeria, Salmonella and Escherichia coli O157:H7 in Colorado rural households
(Colorado State University. Libraries, 2009) Rodríguez Marval, Mawill R., author; Belk, Keith, advisor; Sofos, John, advisor
The household environment has been linked to multiple outbreaks of foodborne illnesses, including listeriosis and salmonellosis. The food handling habits of consumers play a critical role in the food chain continuum, and need to be investigated to better prevent foodborne illnesses that originate at home. The objective of this work was to identify risk factors associated with prevalence of Listeria, Salmonella and Escherichia coli 0157:H7 in the rural household environment, and to provide scientific data for the development of reheating instructions for frankfurters in the home setting. To study risk factors associated with Listeria, Salmonella and Escherichia coli 0157:H7 prevalence in rural Colorado households with or without ruminants, households were recruited, and samples from food and the environment, as well as behavioral data from the primary foods preparer in the house, were collected. Listeria was isolated from refrigerators, kitchen sinks, shoes soles, clothes washing machine and food samples, with higher prevalence in households with ruminants. No sample was found positive for E. coli 0157:H7, and Salmonella was isolated from one refrigerator, one washing machine, one working glove, and two shoe samples. Results indicated that behavior related to handling and cooking of perishable foods affected the probability of household samples testing positive tor Listeria, regardless of presence of ruminants. Personal cleanliness habits were related to presence of Listeria on shoe soles, clothes washing machine, and working gloves. Shoes testing positive in households with ruminants were more frequently associated with multiple positive environmental samples compared to households without ruminants. Results indicated that consumer education on handling and storing perishable foods, and animal handling to prevent contamination of the household through shoes or clothes may reduce prevalence of Listeria in home environments. Two studies evaluated reheating of frankfurters inoculated with L. monocytogenes with or without antimicrobials. In both cases, frankfurters were formulated with or without 1.5% potassium lactate and 0.1% sodium diacetate and were inoculated with a ten-strain composite of L. monocytogenes. After inoculation, frankfurters were vacuum packaged and stored under conditions simulating manufacturing/retail and consumer storage. In one study, after the appropriate storage time, frankfurters were placed in a bowl with water and treated in a household microwave oven. Exposure to high power for 75 s reduced pathogen levels (0.7±0.0 to 1.0±0.1 log CFU/cm2) to below the detection limit (<-0.4 log CFU/cm2) on frankfurters with actate/diacetate. On frankfurters without lactate/diacetate, initial levels of L. monocytogenes (1.5±0.1 to 7.2±0.5 log CFU/cm2) on untreated samples increased as storage in vacuum and aerobic packages progressed. For this formulation, the exposure to high power for 75 s produced reductions between >1.5 and 5.9 log CFU/cm2. Depending on the treatment and storage time, the water used to reheat the frankfurters had viable L. monocytogenes counts of <-2.4 to 5.5±0.5 log CFU/ml. Results indicated that levels of L. monocytogenes contamination <3.7 log CFU/cm2, on frankfurters can be significantly (P>0.05) reduced by microwave oven heating at high power for at least 75 s. Higher contamination levels, such as those found on frankfurters without lactate/diacetate and stored for a prolonged period of time, require longer exposure to microwave heating in order to render the product safe for consumption. In the other study, inoculated frankfurters were treated with hot water after different storage periods to evaluate the destructiveness of different time and water-temperature combinations L. monocytogenes. Treatments at 80°C (60, 120 s) and 94°C (30, 60 s) reduced pathogen counts on frankfurters with PL/SD to at/below the detection limit (<-0.4 log CFU/cm) from initial levels on control (immersed in 25°C water for 300 s) samples. For frankfurters without PL/SD, where pathogen numbers reached 6.1 log CFU/cm2 on 60-day old vacuum-packaged product stored aerobically for 7 days, hot water treatments reduced counts by 1.0 (30 s/80°C) to >6.0 (120 s/94°C and 300 s/94°C) log CFU/cmz. No survivors were detected in the heated water after any treatment (detection limit <-2.5 log CFU/ml). While low levels of L. monocytogenes on frankfurters can be inactivated with short exposure to hot water, increased contamination that may occur as the product ages needs longer times and/or higher temperature for inactivation.
Open Access
Development of a rapid detection assay for Listeria monocytogenes on ready-to-eat meat, food-contact and non-contact surfaces
(Colorado State University. Libraries, 2009) Callaway, Jeffrey Ryan, author; Goodridge, Lawrence D., advisor; Sofos, John Nikolaos, committee member; Nightingale, Kendra K., committee member; Gentry-Weeks, Claudia R., committee member
Many tests are available to detect foodborne pathogens. Tests have been designed to selectively allow the growth of a target organism to facilitate identification using biochemical methods, while others have incorporated biochemical identification into selective media. The resulting tests are rapid, sensitive, specific and cost-effective. Recently, molecular methods have been employed to increase the speed, sensitivity and specificity of identification. However, current molecular methods require laboratory equipment and trained personnel and are not capable of detecting viable organisms. This thesis describes a set of studies designed to develop and evaluate a new detection method for the foodborne pathogen Listeria monocytogenes that is rapid, sensitive, specific, costeffective and simple enough to be used in the field and does not require expensive equipment or extensive training.
Open Access
Effects of pre-slaughter cattle management on postmortem tenderization of beef
(Colorado State University. Libraries, 2009) Gruber, L. Sandra, author; Tatum, J. Daryl, advisor
Two independent studies were used to investigate the effects of pre-slaughter cattle management on postmortem tenderization of beef. In experiment I, relationships between behavioral and physiological symptoms of pre-slaughter stress and beef LM tenderness were examined using calf-fed steers (n = 79) and heifers (n = 77). Pen, chute, and post-transportation behavior scores were assigned to each animal. Physiological indicators of stress included cortisol, epinephrine, creatine kinase, lactate, glucose, heart rate, respiration rate, and rectal temperature. Positive correlations (P < 0.05) between behavior scores and physiological parameters indicated that cattle that exhibited behavioral symptoms of stress also responded physiologically. Mean Warner-Bratzler shear force (WBSF) was positively correlated (P < 0.05) with all 3 measures of stressful behavior (r ≥ 0.23). Plasma lactate concentration at slaughter was associated (P < 0.05) with mean WBSF and response to postmortem aging. In Experiment II, effects of genotype and implant program on LM and gluteus muscle (GM) postmortem tenderization were investigated using crossbred steer (n = 185) and heifer (n = 158) calves. The 3-marker GeneSTAR Tenderness panel was used to determine each animal's genotype. Calves were assigned to 1 of 2 implant programs, conventional or delayed. Steaks from conventionally implanted cattle had WBSF values that were approximately 0.2 kg higher (P < 0.05) than steaks from animals that received a single delayed implant, but only during the early postmortem period (3 to 7 d). For both muscles, a linear effect of genotype on WBSF was detected (P < 0.05). Steaks from cattle with most desirable genotype had WBSF values 0.33 kg lower than steaks from cattle with the least desirable genotype. Pre-slaughter factors (sex, implant program, and genotype) controlled in Experiment II each accounted for less than 10% of the explained variation in tenderness of the experimental population. Results of Experiment I identified behavioral and physiological symptoms of acute pre-slaughter stress that were associated with pH-independent differences in tenderness. Findings from Experiment II suggest that pre-slaughter cattle management can impact beef tenderness, but the factors evaluated only accounted for a small proportion of variation in beef tenderness for the experimental population.
Open Access
Use of video image analyses to identify carcass characteristics and sensory quality of beef products generated from mature cow carcasses
(Colorado State University. Libraries, 2009) Woerner, Dale R., author; Belk, Keith E., advisor; Tatum, J. Daryl, advisor
A single study (sponsored by the beef check-off) was conducted to investigate the ability of video image analysis technology to identify carcass characteristics and sensory attributes of products generated from mature cow carcasses. Market cows representing three pre-harvest management strategies were used to evaluate the ability of video image analysis (VIA) to identify the impacts of pre-harvest management (MGMT) on carcass muscle and beef sensory characteristics. Cow MGMT groups were as follows: (1) Non-fed cows (n = 104) (NON-FED; beef-type cows entering the slaughter facility as culls from sale barns and/or ranching operations); (2) Fed cows (n = 108) (FED; beef-type cows entering the slaughter facility from a finishing yard having received a corn-based, high energy diet for a 95 d ± 1 d period); (3) Dairy cows (n = 113) (DAIRY; cows entering the slaughter facility directly from dairies as culls). FED market cows were fatter, heavier, and more muscular than either NON-FED or DAIRY cows. DAIRY cows were slightly fatter (in the carcass), heavier, and less muscular (alive, muscle score) than were NON-FED beef cows. FED beef cows had the most desirable lean color scores, the most tender LM steaks, and had whiter colored fat than NON-FED beef cows. DAIRY cows were the most youthful (lowest SKELMAT and dentition scores) at the time of harvest and produced carcasses that had similar marbling and fat color scores to those of FED beef cow carcasses. NON-FED beef cows produced the lowest marbling scores, the toughest LM steaks, and the most yellow colored fat. Correspondingly, fat from NON-FED beef cows had the highest concentrations of vitamin A and 3-carotene in the fat. NON-FED cows had the greatest probability of producing beef with undesirable flavor attributes but no meaningful differences were found among MGMT groups in fatty acid composition. Cow LM representing all MGMT groups responded to postmortem muscle-aging (P < 0.001) whereas the PM did not (P = 0.075). A MGMT x postmortem muscle aging time interaction existed for the INFRA (P < 0.042). A significant interaction of MGMT x evaluation method (USDA grader vs. VIA instrument) existed for marbling score, LMA, and 12th rib fat thickness. Compared to USDA grader determined values, VIA instrument scores were higher for marbling score and lower for LMA. A prediction model developed from VIA instrument outputs demonstrated the ability to characterize the MGMT of cow with less than 13% error. The findings of this research warrant the continued development VIA instruments to identify cow carcass characteristics and sensory quality.
Open Access
Application of yeast technology in ruminant nutrition
(Colorado State University. Libraries, 2009) Swyers, Kelcey L., author; Archibeque, Shawn L., advisor
This research aimed to evaluate two types of yeast technology applications that are commercially available to feed in the diets of beef cattle; these two applications are dried distiller's grains with solubles (DDGS) and yeast culture (YC). First, DDGS were offered as a protein and energy supplement to pregnant range cows to evaluate performance, and nitrogen and trace mineral status of cows and calves (Exp. 1), then YC was fed as a natural alternative to an ionophore to heavy-weight yearling beef steers fed finishing diets consisting of 19.7% DDGS to evaluate growth performance, carcass merit, cost of gain (COG) (Exp. 2), and fecal prevalence of the foodborne pathogen, E. coli O157:H7 (Exp. 3). In Exp. 1, supplementing the diets of pregnant beef cows maintained on dormant winter range with DDGS improved cow performance, had limited impact on nitrogen or mineral status, and was more economical to feed than the control diet (standard range cubes). In Exp. 2, we found that feeding YC may improve carcass characteristics of steers finished at lower end weights, which could result in fewer days on feed; however, there was no advantage on growth performance or COG. Lastly, Exp. 3 indicated that feeding YC decreased, but did not eliminate, fecal shedding of E. coli O157:H7 upon initial application.
Open Access
Understanding the relationships between swine behavior, physiology and management to improve animal welfare, reduce in-transit losses and improve meat quality in swine
(Colorado State University. Libraries, 2009) Edwards, Lily Nowell, author; Grandin, Temple, advisor; Engle, Terry E., advisor; Rollin, Bernard E., committee member; Anderson, David B., committee member
The objective of these studies was to determine the relationship between pre-slaughter management, physiological measures, and meat quality using commercial swine marketing practices. Experiments 1 & 2 were conducted to determine the effects of distance moved at the farm, time of lairage in holding pens prior to slaughter and distance moved from lairage pens to the stunning area on blood lactate concentration ([LAC]), rectal temperature and meat quality. Both [LAC] and temperature changed during the marketing process (P< 0.0001). The highest [LAC]s were observed at loading and exsanguination. Longer distance resulted in higher [LAC] during loading (Exp. 2). Unexpectedly, longer rest resulted in higher [LAC]s at exsanguination (Exp 1 & 2) and at the end of lairage (Exp. 2). An increase in [LAC] during loading reduced glycolytic potential (Exp. 2) and had a positive impact on meat quality measures, i.e. decreased drip loss, increased 24 hr pH and trends for lower L* and higher visual muscle color score (Exp 1 &2). Specific measurements of pre-stun handling, jamming, rearing, vocalization, electric prod use, backing up, were found to be correlated with exsanguination [LAC] (P<0.05). Experiment 3 evaluated the persistence of blood changes in swine during the marketing process following alteration of dietary electrolyte balance (dEB). Experimental pigs were assigned to a Low (121 meq/kg) or High (375 meq/kg) dEB diet ad libitum for 3 days prior to slaughter. Prior to transport, animals were fasted in the barn for 10 h, then shipped to the plant, rested for 8 h and slaughtered. Blood was sampled four times, initial and final weights were obtained and meat quality parameters were measured. Increasing dEB had no adverse effects on growth performance, meat quality, carcass yield or incidence of pars esophageal ulcer scores. Exsanguination [LAC] was negatively correlated to 60 min pH (r = -0.32, P = 0.0004) and positively correlated (r = 0.21, P = 0.02) to drip loss. These results suggest that exsanguination [LAC] is predictive of the rate of early post-mortem metabolism. This study demonstrated that the effect of dEB on blood parameters was not maintained following a 10 h feed withdrawal (P > 0.22). Therefore, it is likely that the animal‟s ability to withstand any increased metabolic acid load associated with the stress of transport was lost following feed withdrawal. This research supports the use of LAC as a sensitive tool to determine changes in handling and management. These studies emphasized the impact that pre-slaughter management has on physiological parameters of swine throughout the entire marketing process.