Baier, Faith Susan, authorGrandin, Temple, advisorEdwards-Callaway, Lily, advisorEngle, Terry, committee memberRollin, Bernard, committee member2019-09-102019-09-102019https://hdl.handle.net/10217/197329Physiological and behavioral parameters are commonly used to assess cattle welfare. The overall objective of these studies was to understand the impact of animal-based characteristics and the presence of a metabolic disease on the overall well-being of beef feedlot steers through the measurement of physical and physiological parameters. The objective of Experiment 1 was to determine the impact of hair color and length, and animal age on hair cortisol concentration in beef feedlot steers. Nineteen beef crossbred steers were used for this study. Seven of the steers (1,043 ± 6.8 kg; approx. 9 years of age) were fitted with ruminal fistulas and duodenal cannulas and classified as old steers. The other twelve steers (680 ± 4.5 kg; approx. 2.5 years of age) were fitted with only ruminal fistulas and classified as young steers. One steer was euthanized due to health problems within the first week of the study. Steers were categorized into one of three groups: old with black hair (OB, n = 3); old with white hair (OW, n = 3); young with black hair (YB, n = 12). Hair samples from the right rump region of each steer were collected throughout a period of six weeks from six different areas. Only samples collected during Week 6 were used for analyses. Older steers exhibited greater hair cortisol concentrations than younger steers (P < 0.001). The white hair of the old steers yielded higher concentrations of hair cortisol as compared to black hair from young steers (OW = 10.89 ± 2.03 pg/mg and YB = 0.98 ± 0.11 pg/mg, respectively; P < 0.001). Hair cortisol concentration was not impacted by duration of growth (P = 0.33). However, cortisol concentrations exhibited a weak, positive correlation with hair length (r = 0.33, P = 0.01). Additionally, the average hair growth per week of beef steers in the winter months was calculated to be 0.90 mm. Further research should be performed to improve our understanding of the effect of hair characteristics on hair cortisol concentrations as related to the well-being of cattle. The objective of Experiment 2 was to evaluate the relationship between liver abscess presence and stress-related parameters in beef feedlot cattle, utilizing both physiological (hair and serum cortisol, ocular temperature) and behavioral measurements (mobility scoring). The ultimate goal of the study was to establish an initial understanding of the welfare state of cattle with liver abscesses so that management practices can be maintained or changed to allow for the production of cattle to be continually practiced in an efficient and sustainable manner. Three hundred and sixty-three beef breed, Bos taurus feedlot cattle were categorized by the liver abscess score assigned during the slaughter process. The liver abscess scoring groups were: no liver abscess presence (NLA; n = 316); mild liver abscess presence (MLA; n = 21) and severe liver abscess presence (SLA; n = 24). Two animals were unable to be assigned liver abscess scores. No relationships were identified between the presence of liver abscesses and the measured parameters – ocular infrared thermography (P = 0.55), hair cortisol (P = 0.96) and serum cortisol (P = 0.21). Furthermore, hair color was not statistically significant when compared across liver abscess scores (P = 0.70). All animals exhibited normal mobility with no visual signs of lameness. The data indicate that under the conditions of this experiment, where adhesions to the body wall were not tabulated, liver abscesses did not impact measured stress-related outcomes. Additional research is necessary to understand the impact of liver abscess presence on other stress-related parameters associated with well-being in cattle. Further research should be performed to increase our understanding of feedlot cattle welfare, in relation to all associated factors – health and disease, environment, and management-related. Both studies also concluded that future research should be focused on establishing benchmark values of hair cortisol concentration for other applications and validations such as hair sampling techniques, metabolite analysis methodology, and potential health indicators.born digitalmasters thesesengCopyright and other restrictions may apply. User is responsible for compliance with all applicable laws. For information about copyright law, please see https://libguides.colostate.edu/copyright.cattlestresscortisolanimal welfareText