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Item Childhood trauma exposure, age and self-compassion as predictors of later-life symptoms of depression and anxiety in an American Indian sample(Montana State University - Bozeman, College of Letters & Science, 2023) Larsen, Jade Michael; Chairperson, Graduate Committee: Neha John-HendersonPast research has established a relationship between childhood trauma and later-life anxiety and depression symptoms in American Indian samples. However, less is known about protective factors that may reduce the strength of this relationship. The purpose of the present study was to assess self-compassion as a protective factor with an emphasis on age as additional potential moderator. Seven hundred and twenty-nine self-identifying American Indian participants completed self-report measures pertaining to this question online via Qualtrics. The hypotheses were such that self-compassion would be protective against later-life anxiety and depression symptoms at all age points (Hypothesis 1), that the interaction between self-compassion and childhood trauma exposure would be statistically significant for those higher in trauma but not lower (Hypothesis 2) and that there would be a three-way interaction among self-compassion, age and childhood trauma exposure, such that age would moderate the interaction between childhood trauma exposure and self-compassion in predicting symptoms of anxiety and depression (Hypothesis 3). Regression analyses found support for Hypothesis 1, indicating that self-compassion is protective against anxiety and depression symptoms in this sample. Support for Hypothesis 2 was not found, as the interaction between self-compassion and childhood trauma exposure did not significantly predict anxiety or depression symptoms. Hypothesis 3 was supported in that the three-way interaction significantly predicted both later-life anxiety and depression symptoms, such that older participants who reported high levels of self-compassion tended to have the lowest symptoms. These findings indicate that self-compassion may have age dependent effects in moderating the relationship between childhood trauma exposure and later-life symptoms of anxiety and depression in American Indian samples.Item The influence of anxiety, age, and retrieval demands on memory(Montana State University - Bozeman, College of Letters & Science, 2021) Whillock, Summer Rain; Chairperson, Graduate Committee: Michelle L. MeadeThe present dissertation sought to determine if anxiety and hypervigilance can be activated outside the confines of specifically threatening stimuli by examining different situational pressures such as age and retrieval demands. In both experiments, participants studied categorized word lists and were randomly assigned to complete an initial recall test under free, forced, or warning (Exp. 2) recall instructions, followed by a second test under free recall instructions, and a final recognition test. For older adults, forced recall influenced the relationship between trait anxiety and memory such that heightened levels of trait anxiety were associated with greater correct recall and lower false recognition. In contrast, for younger adults, free recall influenced the relationship between memory-specific anxiety, hypervigilance, and memory such that heightened levels of memory-specific anxiety and hypervigilance were associated with lower levels of correct recognition. Further, warning recall influenced the relationship between memory-specific anxiety and memory in young adults, such that heightened levels of memory-specific anxiety were related to greater correct recall at test 1. Across two experiments, results show that it is possible for situational pressures to influence the relationship between anxiety and memory in the absence of specifically threatening stimuli. Additionally, the relationship between anxiety and memory depends on age, the type of anxiety being measured, and the retrieval demands of the task.Item The influence of dam age and heifer post-weaning voluntary feed intake on subsequent production, reproduction and lifetime productivity of Angus beef females(Montana State University - Bozeman, College of Agriculture, 2022) Wellnitz, Krista Rose; Chairperson, Graduate Committee: Megan Van Emon and Timothy DelCurto (co-chair); This is a manuscript style paper that includes co-authored chapters.Limited research has been done to evaluate the impacts of dam age or post-weaning voluntary feed intake and its impact on subsequent performance and longevity in the beef herds, specifically female offspring. Therefore, the objectives of this research were to investigate how dam age and post-weaning voluntary feed intake influences lifetime productivity of commercial Angus females. First-calf heifers and mature cows were used to conduct three studies. Results indicate that classification of replacement heifers based on intake as a heifer had little to no impact on subsequent productivity as a mature female, while dam age had a greater influence overall. Productivity as a measure of total pounds of calf weaned through 5 yrs indicated that cows from dams that were 8-yr old or older weaned more total pounds of calf than cows from 3- yr old dams. Results indicated that heifers classified as low intake heifers, had greater mature BW at breeding and greater BCS than cows that were classified as average or high intake as heifers. However, DMI expressed as g/kg of BW displayed no differences with respect to cow age. Milk production was influenced by post-weaning intake for 2 and 5-yr old cows. The dam age study, indicated that dam age will affect future outcomes of replacement heifers. Cow BW at weaning displayed significance for dam age with cows born from 5- and 8-yr old and older dams having greater BW than cows born from 2-yr old. Cow yearling weight was significant for dam age with cows from 5-, 6/7-, and 8-years and older dams having greater yearling weights than cows from 2- and 3-yr old dams. The probability of remaining in the herd at 5-yr old varied across dam age groups with cows from 2-yr old and 5-yr old dams having greater probability to remain in the herd than the other age groups. Therefore, our research suggests that selection of replacement heifers based on post-weaning voluntary feed intake at 45 d post-weaning is not a strong indicator of lifetime productivity. Instead, cow age has a greater impact on lifetime productivity than heifer post-weaning voluntary feed intake.Item Spatial and temporal dynamics of conifer expansion in southwest Montana(Montana State University - Bozeman, College of Agriculture, 2022) Haygood, Nathaniel Paul; Chairperson, Graduate Committee: Craig Carr; This is a manuscript style paper that includes co-authored chapters.Since the mid-19th century, pinyon-juniper woodlands in western North America have experienced an expansion in range and density and a corresponding degradation in the provision of ecological goods and services including forage production, watershed function, biological diversity, and habitat values. While this is well-documented in other systems, there is little information characterizing shifts in tree range and abundance within the northern extent of these juniper and pine woodlands. The purpose of this research project was twofold: 1) identify and improve understanding of Rocky Mountain juniper and limber pine age distribution and compare these data to other systems, and 2) evaluate understory dynamics along the gradient of woodland development to assess impacts to understory species composition and abundance, as tree densities and range increase. We aged 278 trees across 38 plots in southwest Montana. We recorded soil moisture throughout the growing season (May-July), aspect, elevation, soil texture, herbaceous production and diversity, and tree density and canopy cover from 2019-2021. Greater than 95% of all trees were under 100 years old and the oldest tree (juniper) was 247 years old. Across the study site, limber pine was younger than Rocky Mountain juniper and appeared to prefer different sites. Maximum and mean juniper age was higher on dry sites with high sand content and lower on moist sites with low sand content in the top 15cm of the soil profile. Understory shrub and cool-season perennial grass cover was negatively influenced by heavy tree canopy cover on southwest to southeast aspects. The results from this study indicate 1) limber pine and Rocky Mountain juniper generally occupy different sites, 2) juniper and pine stand age is lower on north facing aspects with coarse soils and higher soil moisture content in late spring and early summer. Currently, increasing conifer dominance on north facing aspects appears to minimally impact cool-season perennial grass cover and production. Comparatively, increasing conifer dominance on south facing slopes may reduce cool-season perennial grass and shrub cover and production. We recommend the inclusion of these findings, as land managers seek to sustain delivery of necessary ecological goods and services.Item Methodological considerations and clinical utility of analyzing transient behavior in quiet stance postural control(Montana State University - Bozeman, College of Engineering, 2020) Reed, Cody Aaron; Chairperson, Graduate Committee: Scott Monfort; Ajit M.W. Chaudhari, Lise C. Worthen-Chaudhari, Kimberly E. Bigelow and Scott M. Monfort were co-authors of the article, 'A new perspective on transient characteristics of quiet stance postural control' in the journal 'PLOS ONE' which is contained within this thesis.; Scott M. Monfort were co-authors of the article, 'Influence of a cognitive perturbation on transient characteristics of quiet stance postural control' submitted to the journal 'Gait & posture' which is contained within this thesis.Postural control has been widely studied to provide insight into various health concerns. Traditionally, postural control is assessed using whole-trial analysis techniques that measure center of pressure parameters as a singular estimate for an entire trial. These whole-trial estimates may be more reliable for longer duration trials. However, longer trials and whole-trial analyses mask transient (i.e., a destabilized period followed by a transition to a more stable, quasi-steady state level) responses within center of pressure data. By only using whole-trial estimates, we may be missing out on unique information that is contained within this understudied aspect of postural control. Therefore, four experiments were conducted to better understand the clinical utility of evaluating transient postural control behavior. The first experiment tested whether transient, epoch-based characteristics of center of pressure parameters provided unique information compared to traditional whole-trial estimate approaches. The second experiment evaluated participants in eyes open and closed conditions to test whether transient behavior was a sensory reweighting response to eye closure. The third experiment tested whether transient characteristics of postural control could distinguish between younger and older adults. Based on the results of the first three experiments, a fourth experiment was conducted to investigate the influence of cognitive perturbations on transient characteristics of postural control. Negligible correlations were found between transient characteristic and whole-trial estimates, indicating that unique information is contained in transient measures of postural control. Although transient behavior was exaggerated during eyes closed stance, transient behavior still existed during eyes open stance. In addition, select transient characteristics distinguished between young and older adult groups, supporting the clinical relevance of transient measures. Lastly, cognitive perturbations influenced transient postural behavior, supporting the use of transient measures for analyzing dual-task scenarios. Overall, our results support the use of epoch-based estimates to characterize transient postural behavior as a complementary assessment to traditional whole-trial analyses. Our results also indicate the need to carefully consider how postural control trials are analyzed and initiated. Moving forward, further evaluation of transient characteristics of postural control is warranted to determine their relationship to health outcomes such as falls.Item Evaluation of sustained release mineral boluses as a long-term nutrient delivery method for beef cattle(Montana State University - Bozeman, College of Agriculture, 2021) Carlisle, Tanner Jay; Chairperson, Graduate Committee: Timothy DelCurto; Samuel A. Wyffels, Steve D. Stafford, Anna R. Taylor, Megan L. Van Emon and Timothy DelCurto were co-authors of the article, 'Evaluation of sustained release mineral boluses as a long-term nutrient delivery method for beef cattle' in the journal 'Animal feed science and technology' which is contained within this thesis.Two studies were conducted to evaluate the efficacy of sustained release mineral boluses as an alternative nutrient delivery method for beef cattle. For both studies 16 ruminally-cannulated cows were used in a completely randomized design. In study 1, we evaluated degradation rates of two bolus prototypes and cow age (2-yr-old versus 3-yr-old cows) over an 87-d study period. In study 2, we evaluated two bolus types (90-d degradation target versus 180-d degradation target), as well as two diet qualities contrasting low-quality high-fiber forage (> 65% NDF and < 8% CP) and high-quality low-fiber forage (< 55% NDF and > 15% CP). For both Studies intake and digestion periods were conducted to evaluate cow age (study 1) or diet quality (study 2) effects on intake and rumen/reticulum function. In study 1, models containing an asymptotic effect of day and an interaction between day and bolus type received virtually all support of candidate models for bolus degradation rate. Cow age did not affect bolus degradation rates (Beta = -0.81 + or - 1.13; P= 0.48) and degradation rates were greater for bolus prototype B compared to bolus A (Beta prototype B = -20.39 + or - 1.13; Beta prototype A = -9.64 + or - 0.81; P < 0.01). In study 2, models containing a linear effect of day and an interaction between day and diet received virtually all support of candidate models for the degradation rate of the 90-d and 180-d prototype. In addition, both bolus protoypes displayed a diet quality + or - time interaction (P < 0.01) for bolus degradation rate. Cattle treated with the 90-d bolus and fed a high-quality diet had greater degradation rates (Beta High-quality = -2.64 + or - 0.08; Beta Low-quality = -1.97 + or - 0.10; P < 0.01) than the cows that were fed a low-quality diet. In contrast, cattle treated with the 180-d bolus expressed greater degradation rates (Beta Low-quality = -0.09 + or - 0.007; Beta High-quality = -0.04 + or - 0.005; P < 0.01) with cows on the low-quality diet versus the high-quality diet. Across both studies, two of four bolus prototypes met target release rates at 90 days. However, bolus degradation characteristics varied and were influenced by diet quality.Item Variation of life-history strategies in pinnipeds with an emphasis on survival rates and spatial distribution of male Weddell seals in Erebus Bay, Antartica(Montana State University - Bozeman, College of Letters & Science, 2020) Brusa, Jamie Louise; Chairperson, Graduate Committee: Jay J. Rotella; Jay J. Rotella, Robert A. Garrott, J. Terrill Paterson and William A. Link were co-authors of the article, 'Variation of annual apparent survival and detection rates with age, year, and individual identitiy in male Weddell seal (Leptonychotes weddellii) from long-term mark-recapture data' in the journal 'Population ecology' which is contained within this dissertation.; Jay J. Rotella, Katharine M. Banner and Patrick R. Hutchins were co-authors of the article, 'A comparative study evaluating how stage-specific survival rates vary with life-history traits in male pinnipeds' submitted to the journal 'Journal of evolutionary biology' which is contained within this dissertation.; Jay J. Rotella was a co-author of the article, 'Influence of age and individual identity in the use of breeding colony habitat by male Weddell seals (Leptonychotes weddellii) in Erebus Bay, Antarctica' submitted to the journal 'Journal of mammalogy' which is contained within this dissertation.This dissertation explores various components of male life-history theory using a species-specific approach focusing on Weddell seals (chapters 2 and 4) and a comparative approach focusing on pinniped (seal and sea lion) species (chapter 3). To better understand how marine mammal populations can function and to gain insight about the evolution of male Weddell seal fitness, my coauthors and I estimated the age-specific survival rates of male Weddell seals living in Erebus Bay, Antarctica. Actuarial senescence (decreasing age-specific survival with increasing age) has been documented for several wildlife species. However, contrary to females, little information exists regarding age-specific patterns of survival, including actuarial senescence, for males. We used 35 years of mark-recapture data to estimate age-specific survival rates in male Weddell seals using a hierarchical model approach in a Bayesian framework. We found that male survival estimates were moderate for pups and yearlings, highest for 2-yearolds, and gradually declined with age thereafter such that the oldest animals observed had the lowest survival rates of any age, illustrating that male Weddell seals in this population exhibit actuarial senescence. We further investigated male Weddell seal ecology by describing the spatial patterns of male Weddell seals in Erebus Bay using regression modeling and kernel density methods. The intermediately aged males tended to have the most reproductive-age female neighbors, but individual heterogeneity played a stronger role than age. We found that younger males tended to settle in more offshore and less crowded areas of the habitat relative to older males. From a comparative approach, we assessed the patterns of tradeoffs among various fitness traits in male pinnipeds by examining the relationships between stage-specific survival rates and body size, baculum size, mating strategies, and delayed social maturity. Comparative studies similar to ours have tended to focus on females of avian and some terrestrial species and have mostly addressed reproductive traits. However, we lack information about males and connections between survival rates and other life-history traits. We found evidence for a relationship between precopulatory, rather than postcopulatory, traits and survival rates. We highlight the need for more empirical survival rate data and robust comparative methods.Item Coordination and coordination variability during running with respect to internal loading and age(Montana State University - Bozeman, College of Education, Health & Human Development, 2021) Hoffee, Allison Jane; Chairperson, Graduate Committee: James P. Becker; David Graham, Scott Monfort and James Becker were co-authors of the article, 'Coordination variability predicts achilles tendon and peak patellofemoral loading in healthy runners' submitted to the journal 'Clinical biomechanics' which is contained within this thesis.; Scott Monfort, David Graham and James Becker were co-authors of the article, 'Comparison of coordination and coordination variability between adolescent and adult runners' submitted to the journal 'Journal of sports sciences' which is contained within this thesis.Running is a largely popular and widely accessible form of exercise. However, running may pose risks to individuals due to its associations with high rates of injuries. Coordination between lower extremity joints and segments as well as coordination variability have linked to these running injuries. While mechanisms of injury are multifactorial, one theory suggests that reduced coordination variability may cause injury by increasing cumulative loading of soft tissue structures. This relationship may be important when assessing age, as prevalence of injuries differ between adolescents and adults. Therefore, this thesis aimed to 1) assess the relationship between coordination variability and loads in the Achilles tendon and patellofemoral joint during running 2) and evaluate differences in segmental coordination and variability between adolescent and collegiate runners. In Study 1, 64 healthy, adult runners ran on an instrumented treadmill while kinematics and kinetics were recorded. Coordination variability for knee-shank, knee-rearfoot, and shank-rearfoot couplings were calculated using vector coding. Achilles tendon and patellofemoral kinetics were calculated with musculoskeletal models. Surrogate variables were created for Achilles tendon and patellofemoral metrics using principal component analyses, and regressions were used to determine whether variability metrics predicted loading surrogates. One surrogate variable was created for Achilles loading, and lower knee-rearfoot variability predicted greater Achilles loading. Two surrogate variables were created for patellofemoral loading. Lower knee-rearfoot and knee-shank variability predicted greater peak patellofemoral loading, but no variability predicted cumulative patellofemoral loading. This suggests that a combination of low variability and large loads may be important for injury risk rather than cumulative loading. Study 2 assessed 21 competitive adolescent and 21 collegiate runners. Coordination variability was calculated using vector coding for various thigh, shank, and rearfoot couplings. Coordination patterns were analyzed using a binning frequency analysis. Adolescent and collegiate runners displayed different coordination patterns while running that primarily emerged from the transverse plane. Adolescent runners displayed greater coordination variability on average than collegiate runners. Combined with previous literature, this suggests a downward trend in coordination variability starting in adolescence and continuing through adulthood. In conclusion, coordination and its variability may be consequential in terms of injury mechanisms and different age populations.Item Assessment of non-lethal tools to assign sex, stage of maturity, and reproductive condition in Burbot Lota lota(Montana State University - Bozeman, College of Letters & Science, 2019) McGarvey, Lauren Marie; Chairperson, Graduate Committee: Christopher S. Guy; Molly A. H. Webb (co-chair); Christopher S. Guy and Molly A. H. Webb were co-authors of the article, 'Description of gametogenesis and assessment of non-lethal tools to assign sex, stage of maturity, and reproductive condition in burbot Lota lota' which is contained within this thesis.; Christopher S. Guy and Molly A. H. Webb were co-authors of the article, 'Assessment of gonad size measured by ultrasound to assign stage of maturity and reproductive condition in burbot Lota lota' which is contained within this thesis.; Christopher S. Guy and Molly A. H. Webb were co-authors of the article, 'The assessment of non-lethal tools to identify mass ovarian follicular atresia in burbot Lota lota' which is contained within this thesis.Non-lethal tools (plasma sex steroid concentrations and ultrasound) were assessed to assign sex, stage of maturity, and reproductive condition (non-reproductive and reproductive) in Burbot Lota lota from Lake Roosevelt, Washington. Gonadal tissue, plasma samples, and gonadal sonograms were collected from Burbot. Gonadal tissue was processed for histological analysis to describe gametogenesis and confirm sex, stage of maturity, and reproductive condition. Plasma testosterone (T) and estradiol-17beta (E2) concentrations were measured by radioimmunoassay. Plasma 11-ketotestosterone (11- KT) concentrations were measured by liquid chromatography-mass spectrometry. Gametogenesis was described by gonadal histology during the entire reproductive cycle. Plasma sex steroid profiles, gonadosomatic index, and ovarian follicle diameter were also described during the entire reproductive cycle. Plasma 11-KT concentrations were used to assign sex with 81% accuracy during the entire reproductive cycle, and plasma 11-KT and E2 concentrations were used to assign sex with 98% accuracy during the reproductive phase (i.e., November to March in Lake Roosevelt). In females, plasma T concentration, plasma E2 concentration, and month were used to assign stage of maturity with 87% accuracy, and plasma T concentration and plasma E2 concentration were used to assign reproductive condition with 98% accuracy. In males, plasma 11-KT concentration, girth at the urogenital pore, and month were used to assign stage of maturity with 73% accuracy, and plasma T concentration was used to assign reproductive condition with 90% accuracy. Ultrasound was used to assign sex with 97% accuracy, and ultrasound measurements of gonad size were a promising tool to assign stage of maturity and reproductive condition. Non-lethal tools (plasma sex steroid concentrations, gonad size measured by ultrasound, and ovarian follicle diameter) were also assessed to identify mass ovarian follicular atresia in female Burbot. Plasma T concentrations and ovarian follicle diameter were promising tools to identify mass ovarian follicular atresia. Nonlethal tools to assign sex, stage of maturity, and reproductive condition will enable fisheries biologists to assess indices of reproductive potential for the Burbot population in Lake Roosevelt. Indices of reproductive potential can be used characterize and monitor population demographics, improve models of population growth, establish sustainable harvest regulations, monitor the effects of management actions, and monitor the effects of environmental stressors.Item Sources of variation in maternal allocation to offspring during lactation in the Weddell seal(Montana State University - Bozeman, College of Letters & Science, 2018) Macdonald, Kaitlin Rose; Chairperson, Graduate Committee: Jay J. RotellaVariation in the allocation of energy to reproduction by mothers can have fitness consequences for mothers and offspring. Diverse features of a mother, and annual environmental fluctuations may affect the amount of energy a mother allocates to offspring and may obscure age-specific patterns that are of interest when evaluating predictions made from existing life history theory. To properly evaluate possible sources of variation, especially age-specific variation in maternal allocation, analyses of data for known-age mothers with a wide range of ages, diverse reproductive histories, and multiple measures of allocation to reproduction are needed. We used data from a long-term study of Weddell seals that were individually marked as pups and monitored annually and a Bayesian hierarchical modeling framework to characterize age-specific variation in maternal allocation and test predictions about age-specific variation while considering additional maternal features that might influence maternal allocation. Based on masses for 311 mothers and associated pups from 2002 to 2016, we found that maternal allocation was moderately associated with maternal age and strongly associated with maternal body mass at birth of her pup. We found that heavier mothers lost a greater proportion of mass during the entire lactation period but that the efficiency with which mothers transferred this mass to their pups was lower than that of lighter individuals. The proportion of mass lost by a mother during the entire lactation period was greater for mothers that had reproduced the previous year and for those who started reproducing young, which suggests that individual quality and perhaps experience are determinants of maternal allocation in this species. Our study did not find support for our predictions that older mothers would allocate more body reserves, be more efficient at transferring mass during early lactation, or alter their behavior in ways that would improve mass transfer efficiency during late lactation, relative to prime-age mothers. The large variation we found in energy allocation to pups translates to large variation in pup weaning mass. Our results highlight that maternal multiple features should be considered when evaluating patterns of age-specific variation in maternal allocation.