Įtariant skydliaukės patologiją rekomenduojama tirti tirotropinio hormono ir laisvo tiroksino koncentracijas kraujo serume. Laisvo trijodtironino tyrimas nėra įprastinis ir atliekamas kai nustatoma sumažėjusi tirotropinio hormono ir normali laisvo tiroksino koncentracija. Šio darbo tikslas - įvertinti padidėjusio laisvo trijodtironino poveikio ypatumus, esant normaliai tirotropinio hormono ir laisvo tiroksino koncentracijai. Uždaviniai – nustatyti ir įvertinti klinikinių simptomų ypatumus, objektyvaus tyrimo duomenis (odos būklę, skydliaukės padidėjimo laipsnį, širdies ir kraujagyslių sistemos rodmenis), laisvo trijodtironino padidėjimo sąsajas su antikūnų prieš skydliaukės peroksidazę, tirotropino receptorius, tiroglobulino kiekiu, su skydliaukės hormonus nešančio baltymo indeksu, kepenų fermentų koncentracijos pokyčiais, skydliaukės mazginių pokyčių dažnį ir palyginti juos su pacientų, kai nėra hormonų koncentracijos pokyčių, arba izoliuotai padidėjęs tik trijodtironinas, ar nustatyta tirotoksikozė. Nustatyta, kad padidėjus laisvam trijodtironinui, kai tirotropinio hormono ir laisvo tiroksino koncentracija serume normali, būdingi širdies ir kraujagyslių sistemos ir emocinės būsenos sutrikimai, objektyviai dažniau apčiuopiama padidėjusi skydliaukė. Statistiškai reikšmingų sąsajų tarp padidėjusio laisvo trijodtironino ir minėtų laboratorinių rodiklių, mazginių pakitimų skydliaukėje nenustatyta. / Accordind to world guidelines of thyroid function testing, it is suggested to use only ultrasensitive thyrotropin measurement in order to determine the diagnosis of hyperthyroidism. Free triiodothyronine is not a routine test. A serum level of free triiodothyronine is tested only when the thyrotropin concentration is decreased. For the first time in Lithuania, the study was made in order to investigate clinical features of symptoms, the degree of thyroid increment, cardiovascular system data, relationship between antibodies against thyroid peroxidase, thyroglobulin and thyrotropin receptors, thyroid binding globulin index, abnormalities of liver enzyme levels, incidence of thyroid nodular lesions associated with the increases in free triiodothyronine, when free thyroxine and thyrotropine levels are within the normal range. In conclusion was found that persons, who had elevated levels of free triiodothyronine, when thyrotropin and free thyroxine concentrations in serum were in normal ranges, suffered from characteristic cardiovascular system and emotional state disorders, there are thyroid volume increase, determined elevated levels of antibodies against thyroid peroxidase and alanine transaminase in serum, but statistically significant link between increased free triiodothyronine and the laboratory parameters was not observed. The increase of free triiodothyronine concentration in serum is not associated with nodal changes in the thyroid gland.

Objetivou-se avaliar a influência da monensina sódica sobre o acúmulo hepático de cobre em ovinos. Haja vista, que ionóforos podem alterar a absorção, disponibilidade e distribuição tecidual de minerais em muitos tecidos do organismo. Foram utilizados 24 ovinos mestiços das raças Santa Inês x Dorper com média de três meses de idade e peso medio de 30 kg ao início do experimento, que receberam dieta basal calculada em 2,75% do peso corpóreo, sendo 50% de concentrado comercial (7,13 ppm de Cu) e 50% de feno de capim coast-cross (3,72 ppm de Cu) e 10 gramas de sal mineral (5,9 ppm de Cu). Os cordeiros foram distribuídos em quatro grupos distintos, sendo: Controle apenas dieta basal; Monensina (Mon) - dieta basal e 30 ppm de monensina sódica; Cobre (Cu) - dieta basal acrescida de 10 mg/kg P.V./dia de cobre, na forma de sulfato de cobre pentahidratado; e grupo Monensina+Cobre (MonCu) - dieta basal acrescida de 10 mg/kg P.V./dia de cobre e 30 ppm de monensina sódica. O período experimental teve duração de 14 semanas. Foram coletadas amostras de figado e bile no início por biópsia, e ao final do experimento por necropsia, para determinação de minerais, assim como amostras semanais de sangue para avaliação bioquímica, hematológica e mineral. Foi realizada análise estatística por meio de fatorial 2x2 considerando como fatores a inclusão ou não de cobre e monensina na dieta. Somente um animal apresentou quadro clínico de intoxicação cúprica acumulativa. As concentrações de cobre no fígado no início do experimento variaram entre 243,8 e 345,4 ppm não havendo diferença entre os grupos experimentais. As concentrações médias e desvios-padrão em ppm do cobre hepático ao final do experimento foram 3.363 ± 576 para o grupo MonCu; 2560 ± 524 para o grupo Cu; 562 ± 168 para o grupo Mon e 253 ± 131 para o grupo Controle. Ao final do estudo a concentração de cobre hepático foi influenciada pela suplementação com cobre (P = 0,0001) e monensina (P = 0,0003). Os grupos suplementados com cobre tiveram redução dos teores de ferro hepático (P = 0,0287) e aumento das concentrações de cobre na bile. A avaliação bioquimica demonstrou elevação da atividade sérica da GGT e AST (P < 0,05) nos grupos Cu e MonCu a partir da décima primeira semana do experimento em relação aos grupos Controle e Mon. O aumento da atividade destas enzimas foram influenciadas pela suplementação de cobre (P = 0,0340), enquanto os grupos suplementados com monensina apresentaram menores valores de creatinina quinase. Os resultados obtidos permitem concluir que a monensina interfere positivamente com o acúmulo hepático de cobre sendo que a sumplentação deste aditivo pode predispor a quadros de intoxicações cúprica em ovinos. / The aim of this study was to verify if monensin can change the accumulation of cooper in the liver of sheep, in view of ionophores can alter the absorption, availability, tiissue distribution of many minerals in the body. Twenty four crossbred Dorper X Santa Inês lambs wiht mean age of 3 months and wheitgh 30 kg at the begining of trial recived a basal diete calculated by 2,75% of body wheigth of 50% concentrade (7,13 ppm of Cu) and 50% cost-cross hay (3,72 ppm of Cu) and 10 g of mineral salt (5,9 ppm of Cu). Lambs were randomly distributed in four groups: Control: basal diet, Mon Group reciving basal diet plus 30 mg of monensin; Cu group: basal diet plus 10 mg Cu B.W of CuSO4.5H2O solution; Group CuMon: basal diet plus 30 mg of monensin and 10 mg of Cu B.W. The exeperimental period lasted for fourteen weeks. Liver samples were obtined by liver biopsy initially and at the end by necropsy when lambs were slaughterd. Blood samples were obtained weekly for determination of biochemical, hematological and mineral. Statistical analysis using a 2x2 factorial was conducted considering the factors copper and monensin in the diet and the interaction between them to evaluate the hepatic copper at the beginning and at the end of the study. Only one of animal of group MonCu exhibit clinical sings of copper toxicosis. Copper concentrations in the liver at the beginning of the experiment ranged between 243,8 and 345,4 ppm with no difference between experimental groups. Mean concentrations and standard deviations in ppm of hepatic copper at the end of the experiment were 3,363 ± 576 for MonCu group; 2560 ± 524 for Cu group; 562 ± 168 for the Mon group and 2538 ± 131 for the control group. At the end of the study liver concentrations and total hepatic copper accumulation were influenced both by the amount of dietary copper (P = 0.0001) and of monensin (P = 0.0003). The groups supplemented with copper had reduced levels of hepatic iron (P = 0.0287) and increased concentrations of copper in the bile. The biochemical evaluation demonstrated elevated serum AST and GGT activity (P <0.05) with Cu and MonCu from the eleventh week of the experiment compared to the control groups and Mon. The increased activity of these enzymes were influenced by copper supplementation (P = 0.0340), while group monensin had lower values of creatinine kinase. The results indicate that monensin interferes positively with hepatic copper accumulation and supplementation of this additive can predispose cupric poisoning in sheep.

Introduction California sea lion (Zalophus californianus) health is severely compromised by domoic acid toxicosis, which occurs in high levels during harmful algal blooms of Pseudonitzschia australis along the coast of California. Current diagnostic protocols are often inconclusive due to a 2-48 hour window of detectability within the urinary, circulatory, and gastric systems (Cook, et al. 2011 and Monte, Pers Comm, 2012). Past studies suggest that Z. californianus, with domoic acid toxicosis, commonly display abnormal behaviors (Goldstein, et al. 2008). However, many of these abnormal behaviors are also associated with other diagnoses and are therefore unreliable as diagnostic indicators. This study fills in a knowledge gap relating to abnormal behavior types and their correlation to domoic acid toxicosis and helps solve the problem of current, inconclusive, diagnostic protocols. In this study, my objectives were to identify abnormal behaviors correlated to domoic acid toxicosis, create a diagnostic ethogram, determine the applicability of the method in the field, and determine the applicability of triage based on the relationship between abnormal behaviors and domoic acid levels. Methods I conducted focal animal continuous scans (continuous observation of a single animal at a time, for a set period) with continuous data entry, on animals admitted to the Marine Mammal Center (main study location during 2011-2013) and the Marine Mammal Care Center (comparison location, 2013). I conducted my observations from behind a blind to prevent both human habituation and behavioral influence of the observer. Observations lasted between 10-15 minutes (10 minutes per pen in 2011, 15 minutes per animal in 2012-2013). Subjects were selected based on an admit date no later than 7 days from the observation date. I conducted focal animal continuous scans at Pier 39, a haul out location, in the San Francisco Bay. Animals included in the study had identifying marks or were isolated from other animals (making them easy to identify). I observed animals once per observation day with a total observation period not exceeding 15 minutes per animal. I logged domoic acid levels in feces, urine, and serum (collected by veterinary staff and analyzed with liquid chromatography and bioassays for the presence of domoic acid). I then compared these results to the types and severity of abnormal behaviors displayed by the domoic acid toxicosis sample. Results Results from data collected at the Marine Mammal Center suggest that head weaving (Wilcoxon, p Results from the Pier 39 study suggest that behavioral criteria may be applicable for ruling out domoic acid toxicosis in groups of animals. However, I did not test the method during times of harmful algal blooms. Therefore, the applicability of the method for use as a diagnostic tool in the field is unknown and further research is required. Results for the triage study were inconclusive. The number of animals that tested positive for domoic acid was small and not suitable for statistical analysis. I suggest further research into triage abilities. Conclusion Based on the results of these studies, I can conclude that behavioral analysis offers a reliable diagnostic tool for rescued Z. californianus. Practitioners can use behavioral diagnostic criteria with confidence for the diagnosis of domoic acid toxicosis in Z. californianus.

Sustainable farming is an integrated practice of crop and livestock production system (integrated crop-livestock system; ICLS) that aims to reduce the environmental impacts of agricultural practices while maintaining the productivity and profitability. The use of one step's byproducts by another is a crucial component of this practice. The continuity and effectiveness of sustainable farming greatly rely on deep understanding of each component and good management strategy. One essential aspect involved in all farming components is the role of microorganisms in mediating the biological processes therein. Thus, understanding the composition and activities of these communities would open up ways to engineer them and optimize the respective processes for better sustainable farming practices. The research presented in this dissertation aimed to characterize the microbial metabolism involved in the ICLS with a broader goal of manipulating these systems to improve sustainable agriculture. We focused on two systems that are widely used in the United States, and employed the analysis of 16S rRNA-V4 element for this purpose. In our first system, we characterized the rumen microbiomes of beef cattle alternately grazing nontoxic MaxQ and toxic KY-31 tall fescue pasture, to understand how these cultivars shape the rumen microbiome and identify microbial species potentially capable of degrading ergot alkaloids for better feed utilization. We found that KY-31 grazing remodeled the rumen microbiome substantially at the cellulolytic and saccharolytic guilds. It suppressed the abundances of Fibrobacter, a major ruminal cellulolytic bacterium, as well as those of Pseudobutyrivibrio and Butyrivibrio, and these losses were compensated by increased occurrences of Eubacterium species. Parts of these new communities lingered once developed, and a different guild composition surfaced upon transfer to MaxQ. We also discovered that most of the observations were not evident at the whole microbiome levels but was identified by analyzing the sessile and planktonic fractions separately. Thus, it showcased the need for analyzing sessile and planktonic segments separately while interrogating a heterogenous microbiome. Finally, we identified several potential ergovaline degrading bacteria such as Paraprevotella and Coprococcus. In our second system, we studied the microbiome composition and associated transformation pathways mediating nitrogen loss in two dairy manure storage systems, the clay-lined Earthen Pit (EP) and aboveground concrete storage tank (CS) on two commercial dairy farms, to develop strategies to minimize these losses. We first developed a catalog of the archaea and bacteria that were present therein based on the 16S rRNA-V4 amplicons from manure samples collected from several locations and depths of the storages. Then, we inferred the respective metabolic capabilities via PICRUSt2 and literature curation, and developed schemes for nitrogen and carbon transformation pathways operating at various locations of EP and CS. Our results showed that the stored manure microbiome composition was more complex and exhibited more location-to-location variation in EP compared to CS. Further, the inlet and a location with hard surface crust in EP had unique consortia. With regards to nitrogen transformation, the microbiomes in both storages had the potential to generate ammonia but lacked the organisms for oxidizing it to nitrate and further to gaseous compounds such as anammox and autotrophic nitrifiers. However, microbial conversion of nitrate to gaseous N2, NO, and N2O via denitrification and to stable ammonia via dissimilatory nitrite reduction (DNRA) seemed possible. Minor quantity of nitrate was present in manure, potentially originating from oxidative processes occurring on the barn floor. Higher prevalence of nitrate-transforming microbes at the near-surface locations and all depths of the inlet were found as a result of this instance. These findings suggested that ammonia oxidation to nitrate started on the barn floor and as manure is being stored in EP and CS, nitrate was lost to the environment via denitrification. For carbon transformation, hydrogenotrophic Methanocorpusculum species were the primary methane producers, and it exhibited higher abundance in EP. / Doctor of Philosophy / Sustainable farming is an integrated practice of crop and livestock production systems that aims to reduce the environmental impacts of agricultural practices while maintaining the productivity and profitability. The use of one step's byproducts by another such as the utilization of arable land to grow forages for livestock grazing or the use of manure as organic nitrogen amendments for crops is a crucial component of this practice. The continuity and effectiveness of sustainable farming greatly rely on deep understanding of each component and good management strategy. One essential aspect involved in all farming components is the role of microorganisms in mediating the biological processes therein. Thus, understanding the composition and activities of these communities would open up ways to engineer them and optimize the respective processes for a better sustainable farming practice. The research presented in this dissertation aimed to characterize the microbial metabolism involved in the integrated crop-livestock system with a broader goal of manipulating these to improve sustainable agriculture. We focused on two systems that are widely used in the United States, and employed bioinformatic analysis of a genetic marker for this purpose. In our first system, we characterized the rumen microbiomes of beef cattle grazing alternately on KY-31 tall fescue, a major grass used in Virginia that carry a toxin-producing fungi, and nontoxic MaxQ tall fescue pasture, to understand how these cultivars shape the rumen microbiome and identify potential microbial species capable of degrading the toxin for better feed utilization. We found that KY-31 grazing remodeled the rumen microbiome substantially, especially affecting microbes responsible for degrading cellulose and starch. Some of these communities lingered once developed, and a different microbial population surfaced upon transfer to MaxQ. Several potential toxin-degrading bacteria were also identified. In our second system, we studied the microbiome composition and associated transformation pathways mediating nitrogen loss in two dairy manure storage systems, the clay-lined Earthen Pit (EP) and aboveground concrete storage tank (CS), to develop strategies to minimize these losses. We first develop a catalog of the archaea and bacteria that were present in the manure samples collected from several locations and depths of the storages based on a genetic marker. Then, we inferred the respective metabolic capabilities and developed schemes for nitrogen and carbon transformation pathways operating at various locations of EP and CS. Our results showed that the stored manure microbiome exhibited more location-to-location variation in EP compared to CS. Oxygen exposure, continuous addition of fresh manure, and the presence of crust at the storage surface gave rise to these unique populations. With regards to nitrogen transformation, the microbiomes in both storages had the potential to generate ammonia but lacked the organisms for oxidizing it to nitrate and further to gaseous compounds. However, microbial conversion of nitrate to gaseous N2, NO, and N2O seemed possible. These observations showcased that ammonia is stable during storage. Nitrate, on the other hand, can be converted into volatile nitrogen compounds via various processes. Thus, it is imperative to limit the level of nitrate in manure prior to placement in the storage, which is potentially originating from oxidative processes occurring on the barn floor.

No description available.

This 2-yr experiment evaluated productivity of wild-type, endophyte-infected tall fescue (E+) and novel endophyte-infected tall fescue (NE) summer stockpiled (SS) pastures and the performance of fall-calving beef cow/calf pairs stocked on each cultivar. Fescue cultivars used were KY-31 and MaxQ for E+ and NE treatments, respectively. Pregnant Simmental x Angus cows (128 total, 64 each yr) were stratified by BW, BCS, and expected calving date and then allotted to 1 of 10 pasture groups within each yr (20 groups total, 10 per treatment). Forage growth was stockpiled from April until the initiation of strip-grazing on August 31 of 2017 and 2018. Cows grazed treatment pastures for 52 d from 23 ± 14 d prepartum to 29 ± 14 d postpartum, and calved on treatment pastures. Forage quadrats were clipped from the grazed and ungrazed portions of each pasture to determine weekly forage mass. Total ergot alkaloid (TEA) concentrations were analyzed for all pastures at the beginning of the experiment and every subsequent 2 wk for E+ tall fescue. Cow BW was recorded on 2 consecutive d and BCS determined at the start and end of the experiment. In yr 2, ultrasound 12th rib fat thickness (FT) was measured at the beginning and end of the treatment period Milk production was estimated using the weigh-suckle-weigh technique at 29 ± 14 d postpartum. Initial TEA concentrations for NE (Yr. 1 = 112 µg/kg; Yr. 2 = 632 µg/kg) were decreased (P ≤ 0.01) compared to E+ (Yr. 1 = 1831 µg/kg; Yr. 2 = 2903 µg/kg). TEA concentrations for E+ pastures did not differ (P < 0.23) by sample date. However, average TEA concentrations were greater for yr 2 than yr 1(P ≤ 0.01). Fescue cultivars were not different (P ≥ 0.06) in forage CP, Ash, Ether Extract, and grazed or ungrazed forage mass. However, differences were observed (P ≤ 0.02) for ADF, NDF, and TDN by fescue cultivar. Cow BW, BCS, and FT at the beginning and end of grazing were not different (P ≥ 0.41) by treatment. Milk production was greater (P < 0.01) for cows grazed on E+. Calving date, calf BW, calf ADG were not different (P ≥ 0.65) by treatment. Neither AI nor overall conception rates differed (P ≥ 0.23) between cultivars. Performance of fall-calving cows pre-exposed to E+ was not hindered when grazed on E+ relative to NE in a SS system. / Master of Science / Wild-type, endophyte-infected tall fescue (E+) is the predominant forage of use for producers within the southeastern United States. Endophyte-infected tall fescue gained notoriety due to its drought and pest resistance as well as climate adaptability. These advantages are the result of a symbiotic relationship with an endophytic fungus that has been shown to decrease in animal performance through the production of toxic ergot alkaloids. Development of improved fescue cultivars provided producers with an alternative forage, known as novel endophyte-infected tall fescue (NE), that maintains the agronomic advantages noted with E+ fescue without negative impacts on animal gain and reproductive performance. In adopting NE tall fescue, producers are faced with the financial challenge of renovating existing stands of E+ with NE fescue; leaving pastures unusable during times of normal grazing behavior. This constraint has highlighted the need to explore forage utilization and strategies that can extend the grazing period that do not require the significant cost of total renovation with NE. Fall stockpiled tall fescue has provided producers an option to extend grazing from late November through February when pasture growth ceases and hay supplementation is normally needed. However, a 60 to 90 d period between summer and fall stockpiled grazing leaves producers looking for an additional strategy to provide standing forage for their herds. Summer stockpiling (SS), is a novel grazing strategy that bridges summer and fall stockpiled grazing through proper accumulation of 25 % of total pasture to help extend producers grazing season. The objective of the current experiment is to evaluate both E+ and NE SS pastures and its effect on animal performance, forage availability, and nutritive value. Cow BW and BCS were measured at the initiation, conclusion, and before artificial insemination. Calf BW and ADG were assessed 48 h post-calving and at weaning. Ungrazed and grazed forage mass was collected weekly, while measurements of ADF, NDF, CP, TDN, ether extract, and ash were measured every 2 weeks. After a 52 d treatment period, forage mass was similar across both cultivars, with ADF, NDF, and TDN favoring E+ tall fescue. Additionally, animal performance across both E+ and NE pastures were similar, however increased milk production was observed for cows grazed on E+. This experiment helps shed light on the concept of strategic renovation. Strategic renovation can be best utilized by producers who are interested in maximizing pasture utilization through rotationally grazing E+ and NE tall fescue pastures. By following this renovation strategy, proper allocation of NE tall fescue during times of enhanced ergotism and E+ tall fescue during low thresholds will develop a more specific rotation thus decreasing renovation costs for producers when ergotism is lowest.

Animal welfare is a major concern among livestock producers in the U.S. Heat stress, particularly, compromises animal welfare and productivity, causing >$2B annual economic loss to producers. The presence of toxic alkaloids within tall fescue (Schedonorus phoenix syn Lolium arundinaceum, syn Festuca arundinacea) plants induces a complex of disorders collectively known as fescue toxicosis. Summer slump, a reduction in animal performance due to heat stress, is common and evident of the symptoms. Various techniques for assessing animal physiological and behavioral responses to heat stress were explored in this dissertation, with particular emphasis on fescue toxicosis and its mitigation strategies. In the first study, the physiological and behavioral responses of heifers was evaluated when grazing either toxic tall fescue with wildtype endophyte (WE) or tall fescue with a novel endophyte (NE). Heifers (n = 24) were assigned to either WE or NE pastures for a 56-d grazing study during the summers of 2020 and 2021. Heifer average daily gain (ADG), intravaginal temperature, and degree of hair shedding were recorded during the grazing period. Blood samples were collected through coccygeal venipuncture and hair was collected from the left rump for cortisol analysis. Ear, tail, and hoof temperatures were collected for each heifer using an infrared thermal imaging camera. In 2020, heifers that grazed NE tall fescue had greater (P = 0.0160) ADG over the season (0.22 vs. 0.12 kg day-1). Hair retention score was greater (P = 0.0029) for heifers that grazed WE tall fescue compared to heifers that grazed NE tall fescue across both years. Heifers that grazed WE tall fescue had decreased ear skin temperature (P = 0.0001), tail skin temperature (P = 0.0058), and hoof surface temperature (P = 0.0075) compared to heifers that grazed NE. Heifers that grazed WE had 0.3-0.9 ºC hotter intravaginal temperatures than heifers that grazed NE, especially during daytime. Hair cortisol levels of heifers that grazed WE tall fescue were greater (P < 0.0001) compared to hair cortisol levels of heifers that grazed NE tall fescue. From 1200h-1700h each day, heifers that grazed WE tall fescue spent 1.5 more (P = 0.0003) hours standing and 0.9 fewer (P = 0.0402) hours lying down compared to heifers that grazed NE tall fescue. These results suggest that heat stress and other physiological changes in heifers grazing WE tall fescue could be mitigated by renovating pastures with NE tall fescue that does not impose any negative effects on grazing animals. The second study explored the potential benefits of consuming condensed tannins as a means of negating the effects of toxic alkaloids in tall fescue. Twelve fall-born steers were assigned to one of the two diet supplement treatments - sericea lespedeza pellets (LES) or sericea lespedeza pellets mixed with polyethylene glycol (LES+PEG) for 12 weeks during the summers of 2020 and 2021. The LES+PEG treatment served as a positive control since polyethylene glycol binds tannins, rendering them inactive in the gastrointestinal system. Animal body weight (BW), hair retention score (HRS), rectal temperature, and thermographic images were collected every 4 weeks. Hair and blood samples were also collected for cortisol analysis. Fecal and urine samples were collected and analyzed for total ergot alkaloid (TEA) concentration. Steers on LES had greater (P = 0.0033) ADG compared to steers on LES+PEG in 2021, but not in 2020 (P = 0.8707). In 2021, HRS was greater (P < 0.05) for steers fed LES+PEG compared to steers fed LES. In 2020, ear skin temperature (P < 0.0001) and hoof surface temperature (P = 0.0382) was greater in steers on LES compared to steers on LES+PEG. Rectal temperatures were lower (P = 0.02905) for steers fed LES compared to steers fed LES+PEG in 2021. Plasma cortisol levels did not differ (P ≥ 0.1566) between LES and LES+PEG treatments for both years. In 2020, hair cortisol levels did not differ (P = 0.8295) between treatments while in 2021, the hair cortisol level of steers on LES+PEG was greater (P = 0.0221) compared to hair cortisol levels of steers on LES. This study indicated some changes in animal physiology in response to dietary supplements containing condensed tannins, but results were inconsistent and further studies are needed to better understand the potential benefits of tannins in reducing the effects of toxic alkaloids consumption. In the third study, behavioral and physiological responses of ewes that grazed either mid-stage hardwood silvopastures or open pasture (OP) were compared. The study site consists of 0.27-ha of black walnut (Juglans nigra; BSP) and honeylocust (Gleditsia triacanthos; HSP) silvopastures and open pasture treatments, each replicated three times. During the summers of 2020 and 2021, thirty-six Katahdin ewes were assigned to one of the treatments for a 6-week summer grazing trial. Ewe weights were recorded for two consecutive days at the beginning and end of the study and intravaginal temperatures were recorded for two consecutive days at every 3-week intervals. Trail cameras captured animal behavior. Blood was collected via jugular venipuncture. Hair grown during the trial was collected from the loin region. Blood and hair cortisol concentrations were determined by ELISA. Ewe ADG was greater in HSP compared to OP (P = 0.0456) but did not differ with BSP (P = 0.4686) across both years. Ewes on OP had hotter (P ≤ 0.0343) intravaginal temperatures than ewes on both silvopasture treatments between 1100h-1700h. Plasma cortisol level was lower in ewes on BSP compared to ewes on OP (P = 0.0400) but did not differ with ewes on HSP (P = 0.6954) across both years. Ewes that grazed OP had greater hair cortisol levels compared to ewes on silvopasture treatments both in 2020 and 2021 (P < 0.0001). In 2020, ewes on BSP spent about 20% more time grazing than ewes on OP (P = 0.0054) while in 2021 ewes on BSP spent about 36% more time grazing than ewes on HSP (P = 0.0014). Ewes on OP spent 400% more time standing than ewes on BSP (P < 0.0001) and 750% more time standing than ewes on HSP (P < 0.0001). Ewe on OP spent 20% less time lying down compared to ewes on BSP (P < 0.0001) and 33% less time lying down compared to ewes on HSP (P < 0.0001). Hair cortisol measures and intravaginal temperature sensors can be utilized as reliable and relatively non-invasive techniques for measuring heat stress response in livestock managed in extensive grazing systems. / Doctor of Philosophy / Heat stress compromises animal welfare and productivity, causing > $2B annual economic loss to producers in the U.S. In the southeastern U.S, heat stress in livestock is largely due both to an environmental condition and to the effect of fescue toxicosis caused by toxic alkaloids. Various management strategies to mitigate the effect of heat stress in livestock due to environmental conditions or due to the effect of tall fescue toxicosis are explored in this dissertation. In the first study, behavioral and physiological responses of heifers that grazed either toxic (WE) or novel (NE) endophyte-infected tall fescue was compared. Heifers that grazed WE tall fescue had lower gains, rough hair coat, higher hair cortisol level (stress measure), cooler extremity temperature, and hotter intravaginal temperature compared to heifers that grazed NE tall fescue. These results suggest that heat stress and other physiological changes in heifers grazing WE tall fescue could be mitigated by renovating pastures with NE tall fescue, a forage cultivar that does not impose any negative physiological effects on grazing animals. In the second study, we tested the effect of condensed tannins in reducing the severity of fescue toxicosis in steers. We fed sericea lespedeza pellets to steers in a study to test this effect. All steers were fed sericea pellets, but pellets for half (6) of the steers were treated with polyethylene glycol, which inactivates the condensed tannins in the sericea lespedeza. In our study, we found that the steers fed the sericea lespedeza had higher temperatures at their extremities (ears and tail), but lower rectal temperatures than the control steers. Interestingly, the steers fed the sericea lespedeza pellets also had slicker hair coats and lower levels of hair cortisol (indicating reduced stress) in the second year compared to the control steers. This study showed some potential of condensed tannins in reducing the effects of fescue toxicosis, but needs further study to better understand the potential benefits of tannins in reducing the post-ingestive effects of fescue toxicosis. In the third study, we compared behavioral and physiological (temperature, hair, and blood cortisol) responses of ewes that grazed either mid-stage hardwood silvopastures or open pastures (OP). Ewes on OP showed signs of heat stress with higher hair cortisol levels and hotter intravaginal temperatures during the daytime compared to ewes on silvopasture treatments. Ewes on OP spent 400% more time standing compared to ewes on BSP and 750% more time standing than ewes on HSP. Ewe on OP spent 20% less time lying down compared to ewes on BSP and 33% less time lying down compared to ewes on HSP. Ewes on silvopasture treatments spent 70% less time drinking water compared to ewes on OP. Trees within the silvopasture systems can alter the micro climatic condition thus creating a suitable environment for livestock. This can ultimately reduce stress and improve overall behavioral and physiological responses of livestock in silvopastures compared to open pastures.

Treatment of endophyte-infected tall fescue [Lolium arundinaceum (Schreb.) Darbysh] with the broad leaf herbicide Chaparral® can mitigate fescue toxicosis and enhance forage quality by suppressing seedhead emergence. Applying the herbicide to fescue pastures also reduces forage mass and promotes severe spot grazing when pastures are continuously grazed. A grazing experiment was conducted with steers (2013) and heifers (2014) to evaluate animal and plant responses in fescue-bluegrass (Poa pratensis L.) mixtures treated with Chaparral to determine the effects of grazing management on pasture carrying capacity, nutritive values, botanical composition, and animal performance. Continuous and rotational (i.e., four subdivisions to provide a 7-d grazing period and a 21-d rest period) grazing treatments were assigned to six, 3.0-ha fescue-bluegrass pastures in a randomized complete block design with three replications. Each pasture had six tester animals, and stocking rates were varied using put-and-take animals. Pastures were grazed from 16 April to 8 July 2013 (Year 1) and 20 May to 12 Aug (Year 2) and cattle were blocked by body weight for allotment to pastures. Pasture carrying capacities were greater (P = 0.07) for rotational compared to continuous pastures across both years. Calves on rotationally grazed pastures had greater average daily gain (P = 0.03) and gain per acre (P = 0.05) than those on the continuous treatment across both years. Canopies of continuously grazed pastures contained less (P = 0.01) tall fescue than those in rotationally grazed pastures. Herbage in pre-grazed paddocks had less NDF and ADF than post-grazed paddocks and continuously grazed pastures in 2013 (P < 0.10), but did not differ in 2014 (P > 0.10). In vitro digestible dry matter was greater (P = 0.07) in pre-graze rotational pastures in 2013 compared with continuous and post-graze rotational, and IVDDM did not differ (P < 0.01) between pre-graze rotational and continuous in 2014, but was greater than post-graze rotational. Crude protein was lower (P = 0.06) in both years in post-graze rotational pasture than in continuous or pre-graze rotational pasture, which did not differ. In 2013, there was no difference (P = 0.60) in root WSC among treatments; however, in 2014, WSC levels were greater (P = 0.01) in rotationally grazed pastures compared with continuously grazed pastures. This grazing experiment indicated that rotational grazing of Chaparral treated fescue-bluegrass mixtures can improve both animal performance and the sustainability of pasture productivity.

Prior work using a contractility bioassay determined that the serotonin (5-HT) receptor subtype 5-HT2A is present in bovine lateral saphenous veins and plays a role in ergot alkaloid-induced vascular contraction in steers grazing endophyte-infected (Epichloë coenophiala) tall fescue (Lolium arundinaceum). A study was conducted to determine what 5-HT receptors are involved in vasoconstriction of bovine gut vasculature. The findings of this study indicate that 5-HT2A is present and may play a role in ergot alkaloid induced vasoconstriction. A second study was conducted to determine if ergot alkaloids were transported in the small intestine. The active transporter, peptide transporter 1 (PepT1), was evaluated for its role in the transport of various concentrations of ergot alkaloids across Caco-2 cell monolayers. Results indicate that CEPH, ERT, EXT, and LSA do move across Caco-2 cell monolayers, but appear to utilize PepT1 at larger concentrations. Overall, the demonstrated presence of 5-HT2A receptors in the bovine gut vasculature established a potential for vascular interference by ergot alkaloids entering the bloodstream through transepithelial absorption.