Master of Science in Biomedical Sciences / Diagnostic Medicine/Pathobiology / Daniel U. Thomson / Auction derived feeder calves (n=1,601; initial BW = 273.5 ± 4.7 kg) were used to examine the effects of delayed administration of the initial steroid implant on health, performance, and carcass characteristics of feedlot cattle. Steers were procured from multiple-source auction markets in the southeastern United States and shipped to a central Kansas feedyard over a 6 week period from December 2009 to January 2010. Steers were rested overnight prior to processing, then were randomly assigned, within arrival block, to 1 of 2 treatments: 1) implanted with Revalor-XS (40 mg estradiol and 200 mg trenbolone acetate) immediately upon arrival (ARRIVAL); or 2) implanted with the same implant after 45 d (DELAYED). Cattle were weighed on a group scale immediately following processing of each block. Feed deliveries were measured using load cells on feed trucks and recorded daily. Cattle were evaluated daily for morbidity and mortality by trained feedyard health personnel. Sick or injured cattle were removed from the home pen for further diagnosis and treatment. Individual animal health data were obtained and recorded daily. Final BW was calculated by dividing HCW by the average dressing percent of the pen. Carcass data (quality grade and yield grade) were obtained by USDA personnel; presence of lung lesions, pleural adhesions, and liver abscesses was evaluated by trained university personnel. Delaying the initial implant tended to reduce morbidity (24.7 vs. 28.5%; P = 0.13) and reduced railer rates (1.8 vs. 3.3%; P = 0.02); however, there were no effects of timing of implant administration (P ≥ 0.31) on rates of retreatment, mortality, lung lesions, or pleural adhesions. Implanting immediately upon feedlot arrival resulted in numerical improvements in ADG and feed conversion, but these differences were not statistical (P ≥ 0.56). Cattle implanted upon arrival had numerically greater HCW and yield grade vs. cattle implanted on d 45; however, these differences were not statistical (P ≥ 0.16). Delaying the initial implant 45 d did not influence animal health, performance parameters or carcass characteristics in high risk feeder calves.

Master of Science / Department of Animal Sciences and Industry / Timothy G. Rozell / Malnourished piglets that suffer from periweaning failure to thrive syndrome (PFTS) may show no signs of respiratory or enteric diseases but may have decreased feed intake and become debilitated after weaning. Euthanasia is a necessary component of swine production as it is sometimes the only option to alleviate suffering of piglets that are born with congenital defects or suffer from PFTS. Fifty-eight nursery-aged piglets were utilized in two experiments to evaluate blood parameter differences between healthy and unthrifty piglets and to compare euthanasia methods. Piglets were categorized into two health groups: healthy or unthrifty. During selection, blood was collected for analysis of blood parameters. Piglets were euthanized 24-32 hours after initial blood sampling and a second sample was collected for comparison. After euthanasia, piglets were necropsied for evaluation of euthanasia on pulmonary lesions. No significant difference in number of pulmonary lesions was found between health groups (P = 0.88). Healthy piglets had higher concentrations of glucose, ionized calcium and sodium, and greater pCO₂ than unthrifty piglets (P ≤ 0.05). Unthrifty piglets showed higher concentrations of hemoglobin and hematocrit (P = 0.0002) than healthy piglets. Piglets were assigned to one of two euthanasia methods to compare electrophysiological and behavioral parameters of hypobaric hypoxia and carbon dioxide gas. Two piglets at a time were euthanized for each method. One animal in the pair was fitted with electrocardiogram and electroencephalogram monitoring devices during euthanasia. Behavioral parameters were also recorded. The average treatment times were 27.4 ± 6.7 minutes for HH and 13.8 ± 5.1 minutes for CO2. Piglets euthanized via CO2 reached an isoelectric state faster than piglets euthanized via HH (P = 0.009). Behavioral observations revealed gasping in 100% of CO2 euthanized piglets during the first five minutes of treatment and only 28.6% of HH euthanized piglets during the same period. During HH, 57.1% of piglets became ataxic in the first five minutes while 76.9% of CO2¬ piglets became ataxic during the same period. Results of this trial indicate that HH may be a lower stress alternative to CO₂ as it causes fewer incidences of aversive behaviors in early stages of treatment.

Doctor of Philosophy / Department of Animal Science and Industry / Chris Reinhardt / Dan Thomson / Bovine Respiratory Disease Complex (BRDC) is the most common and costly disease in feedlot cattle in North America. Annual economic losses are estimated to be US$1 billion due to mortality, reduced performance, and treatment costs. The disease is a multifactorial syndrome caused by a combination of environmental factors, management practices, animal susceptibility, and viral and bacterial pathogens. The objectives of this dissertation were to evaluate two injectable antimicrobials for the treatment and control of BRDC in feedlot cattle, investigation of factors associated with BRDC mortality and morbidity, and to develop control charts based on statistical process control (SPC) principles to monitor cattle mortality rates. Two multi-site prospective studies were conducted to evaluate the comparative efficacy of the administration of gamithromycin and tulathromycin for the treatment and control of BRDC. A total of 2,529 animals were enrolled at two commercial feedlot locations to evaluate the efficacy of the antimicrobials to control BRDC. Morbidity due to BRDC was higher (P = 0.03) among calves receiving gamithromycin compared with those receiving tulathromycin; however, treatments were considered bioequivalent (P < 0.05) for BRDC mortality, case fatality rate and re-treatment rate. Final BW, ADG, DMI and F:G, were similar (P<0.05) between the groups of calves receiving gamithromycin and tulathromycin. For the evaluation of treatment efficacy, a total of 1,049 calves were enrolled in the study. Re-treatment rate was higher among animals treated with gamithromycin compared with those treated with tulathromycin. Treatments were bioequivalent (P < 0.05) for case fatality rate, final BW, and ADG. To evaluate factors associated with BRDC, a retrospective study was conducted to analyze BRDC mortality and morbidity associated with initial body weight, rectal temperature, and castration and dehorning (tipping) at processing. Calves with lighter weights and fever at processing were at greater risk of mortality and morbidity due to BRDC. Also, bulls castrated at processing were at higher risk of developing BRDC. Finally, we developed control charts based on SPC principles to monitor and identify “normal” and special cases of variation of mortality rate. In feedlot cattle, monitoring lots of cattle through SPC principles can be used as a powerful tool for continuous improvement.

Master of Science / Department of Animal Sciences and Industry / Jennifer Minick-Bormann / Cattle temperament has historically influenced selection decisions due to ease of handling. However, temperament may also influence economically relevant traits. The purpose of this study was to investigate relationships between temperament, Bovine Respiratory Disease (BRD) incidence, and resulting carcass merit in feedlot steers. Across a two year period, 2,870 crossbred steers were shipped from a single ranch source to a feedlot. At the time of feedlot placement, as well as at the time of reimplantation, temperament was measured via chute score (CS) and exit velocity (EV). Blood samples were taken upon arrival to the feedlot to determine circulating concentrations of interleukin 8 (IL-8) and cortisol, both of which are involved in immune function. Performance traits, including weight and gains, were measured at feedlot placement (d 0), reimplantation (d 73-100), and again 59 to 70 days later. Recorded carcass data included HCW (HCW), USDA yield grade (YG), marbling score (MS), ribeye area, and lung scores. Phenotypic statistical analysis was performed with SAS statistical software (SAS Inst., Inc., Cary, NC) and genetic parameters were estimated using ASREML (Ver. 3.0, VSN International, Ltd., Hemel Hempstead, UK). The pedigree file included records of 7,177 animals with up to 7 generation of pedigree. Contemporary group (CG, n=11) included initial ranch unit, date of arrival to the feedlot, feedlot pen, and processing dates. Fixed effects included in the model were pre-feedlot entry BRD treatment and CG. Cattle with higher CS at placement subsequently had more BRD incidence (P < 0.01). There was a positive phenotypic correlation between placement CS and blood cortisol concentrations (r = 0.07; P< 0.01), and cattle with higher cortisol concentration contracted BRD more often than their calmer peers (P < 0.05). Circulating IL-8 concentration had no influence on feedlot health. At the time of reimplantation, cattle that had been treated for BRD in the feedlot had lower chute scores (P < 0.001). Heritability estimates for CS at placement, EV at placement, CS at reimplantation, and EV at reimplantation were 0.23, 0.17, 0.19, and 0.27, respectively. BRD incidence had a negative genetic correlation with all measures of temperament recorded at the second processing period.

Master of Science / Department of Clinical Sciences / Daniel U. Thomson / Bovine respiratory disease (BRDC) is a multifaceted disease that causes considerable economic loss in both the beef and dairy industry. However, because there may be lingering effects of BRDC in the dairy industry, the full economic costs of the disease may not be realized. These lingering effects may include an increased departure from the herd, decreased milk production, and decreased reproductive performance. All of these outcomes are affected by multiple variables, but proper statistical modeling can control for many of the different influences. Few studies have attempted to look at the long term effects of calfhood BRDC but consistent associations have not been identified. The objective of this observational, retrospective study was to determine the association between calfhood BRDC prior to 120 d of age and departure from the herd, milk production, and reproductive performance. The association between the occurrence of BRDC with departure from the herd prior to first calving depended on the birth year, but for 5 of the 6 years, animals that contracted BRDC were 1.62 to 4.98 times more likely to leave the herd than animals that did not contract BRDC. In addition, animals that contracted BRDC were also 1.28 times more likely to leave the herd between first and second calving than animals that did not contract BRDC. Furthermore, the age at BRDC occurrence was associated with departure from the herd. Animals that contracted BRDC pre-weaning were 2.62 times more likely to leave the herd prior to first calving than animals that contracted BRDC post-weaning. However, age of BRDC occurrence was not significantly associated with departure from the herd between first and second calving. The occurrence of BRDC during the first 120 d of life was associated with a 233 kg decrease in lactation-one production, but was not significantly associated with production in subsequent lactations. Finally, calfhood BRDC was not significantly associated with a decreased reproductive performance measured by calving interval. In conclusion, calfhood BRDC negatively impacts productivity both prior to and after first calving.

Master of Science / Department of Animal Sciences and Industry / Evan C. Titgemeyer / Seven ruminally cannulated heifers approximately 225 kg initial BW were used in a 7 × 4 Youden square design to determine the effects of different levels of limonene on ruminal Fusobacterium necrophorum populations. Treatments included: 1) control, 2) limonene at10 mg/kg diet DM, 3) limonene at 20 mg/kg diet DM, 4) limonene at 40 mg/kg diet DM, 5) limonene at 80 mg/kg diet DM, 6) CRINA-L (a blend of essential oil components) at 180 mg/kg diet DM, 7) tylosin at 12 mg/kg diet DM. Each period included 11 d with 10 d washouts between periods. Samples were collected on d 0 (before treatment initiation), 4, 7, and 10 for measuring F. necrophorum by most probable number (MPN) method using selective culture medium. Results indicate that CRINA-L (P = 0.52) and tylosin (P = 0.19) did not affect ruminal F. necrophorum populations. Limonene linearly decreased (P = 0.03) F. necrophorum populations, and the optimal dietary concentration for limonene was 40 mg/kg DM. Limonene did not affect ruminal degradation rate of lysine, NH3 concentration, or VFA profiles in ruminal fluid. Limonene was useful for reducing ruminal concentrations of F. necrophorum. It may have potential to control liver abscesses, although further research will be needed to assess the effect of limonene under feedlot conditions.

Master of Public Health / Department of Diagnostic Medicine and Pathobiology / M. M. Chengappa / Rabies is the most deadly disease on earth and has a 99.9% human fatality rate. Rabies kills 61,000 humans annually and results in an economic burden of $124 billion USD annually. Each day 3.3 million people live with the risk of rabies. It is estimated that 95% of human rabies cases are a result of coming in contact with an infected canine, majority of these cases being children 15 years and younger. It is estimated that 1 person every 8 minutes dies of rabies. Rabies is a highly neurotropic disease which attacks the brain and central nervous system. Once clinical symptoms are presented, death is invariably the outcome as no cure exists for rabies. Rabies is 100% preventable in humans by proper wound management and proper administration of prophylaxis. Rabies can be adequately controlled in animal populations by contraception and animal rabies vaccine efforts. Whilst it is known that rabies can be prevented in humans and controlled in animal populations, further scientific efforts are still warranted to fully understand this deadly virus so that a cure can one day be discovered. As human and animal populations continue to grow, so does the cost and burden of this horrific disease. As a result, the importance of prophylaxis and passive immunity are critical in the event of medically managing an exposure, and preventing exposures. The World Health Organization has defined global recommendations for individuals and animals who have received prophylaxis to be adequately protected. Measuring this protection is performed using a variety of approved testing methodologies, virus-neutralizing assays and antigen-binding assays. Whilst the WHO recommendations were defined from clinical studies performed with virus-neutralizing assays, the assumption that these recommendations are suitable for the antigen-binding assays is inaccurate. The testing methodologies, virus-neutralization and antigen-binding, share similarities, as they are measuring an immune response to the rabies virus. However; enough differing characteristics are presented such that exact comparisons cannot be made. Establishing the same standards and recommendations for both testing methodologies will never be sufficient.

Diss. (sammanfattning) Uppsala : Sveriges lantbruksuniv., 2009. / Härtill 4 uppsatser.

Diss. (sammanfattning) Uppsala : Sveriges lantbruksuniversitet, 2008. / Härtill 6 uppsatser.

Diss. (sammanfattning) Uppsala : Sveriges lantbruksuniv., 2002. / Härtill 4 uppsatser.