Mercury is an environmental contaminant of concern, particularly for fish eating populations. The objective of this study was to assess the effects of selenium, vitamin E, and phytate on methylmercury (MeHg) toxicity and kinetics in rats. Results show that increased selenium increases McHg in the liver, kidney, and frontal lobe of the brain, while increased vitamin E increases MeHg in the kidney but lowers McHg in the liver. Increased phytate resulted in a significant increase in MeHg in the frontal lobe. Methylmercury-treated rats on all diets showed an increased trend in muscarinic acetylcholine receptor (mAChR) binding in comparison with untreated rats. There was no change in monoamine oxidase (MAO) activities in all treatment groups. These results suggest that nutrients can alter the toxicokinetics of MeHg but none of them show clear protection in neurotoxicity in adult rats.

Thesis (Ph.D.)--University of California, Davis, 2006. / (UMI)AAI3236039. Adviser: Roberto Sainz. Source: Dissertation Abstracts International, Volume: 67-09, Section: B, page: 4768.

Thesis (Ph.D.)--University of Illinois at Urbana-Champaign, 2007. / Source: Dissertation Abstracts International, Volume: 69-02, Section: B, page: 0811. Adviser: Jonathan E. Beever. Includes supplementary digital materials. Includes bibliographical references (leaves 113-127) Available on microfilm from Pro Quest Information and Learning.

Thesis (Ph.D.)--University of Illinois at Urbana-Champaign, 2007. / Source: Dissertation Abstracts International, Volume: 68-07, Section: B, page: 4186. Adviser: Mike Ellis. Includes bibliographical references. Available on microfilm from Pro Quest Information and Learning.

Thesis (Ph.D.)--University of Illinois at Urbana-Champaign, 2008. / Source: Dissertation Abstracts International, Volume: 69-11, Section: B, page: 6481. Adviser: James K. Drackley. Includes bibliographical references. Available on microfilm from Pro Quest Information and Learning.

Thesis (Ph.D.)--University of Illinois at Urbana-Champaign, 2008. / Source: Dissertation Abstracts International, Volume: 69-11, Section: B, page: 6482. Adviser: Mike Ellis. Includes bibliographical references. Available on microfilm from Pro Quest Information and Learning.

Thesis (Ph.D.)--University of Illinois at Urbana-Champaign, 2006. / Source: Dissertation Abstracts International, Volume: 67-07, Section: B, page: 3515. Adviser: Mike Ellis. Includes bibliographical references. Available on microfilm from Pro Quest Information and Learning.

Thesis (Ph.D.)--University of Illinois at Urbana-Champaign, 2006. / Source: Dissertation Abstracts International, Volume: 67-11, Section: B, page: 6121. Adviser: James K. Drackly. Includes bibliographical references. Available on microfilm from Pro Quest Information and Learning.

Doctor of Philosophy / Department of Animal Sciences and Industry / Evan C. Titgemeyer / Ractopamine is a repartitioning agent that can increase muscle growth and has led to our interest in determining the mechanisms involved in enhancing muscle growth. Therefore, three studies were conducted to determine the impact of ractopamine on growth in cattle. The first experiment evaluated the impact of increasing metabolizable protein supply to finishing heifers fed ractopamine. Three different diets were fed to increase the amount of metabolizable protein reaching the small intestine, and the diets contained urea, solvent soybean meal, or expeller soybean meal as the primary supplemental protein source. From this study it was determined that increasing metabolizable protein supply above that present in typical feedlot diets containing urea and steam-flaked corn is not necessary to improve responsiveness to ractopamine. The second experiment evaluated the effect of feeding ractopamine to growing Holstein steers implanted with trenbolone acetate/estradiol. Half of the steers were implanted 28 days prior to all steers receiving ractopamine for the final 28 days; this model represents an intense implant program. The mode of action of the ractopamine and of steroidal implants was different based on their different effects on serum insulin-like growth factor (IGF)-I and longissimus expression of IGF-I mRNA. Additionally, administering a combination of the two growth promotants, based on nitrogen retention, yields a less than additive response using our model of growing Holstein steers. The third study was conducted to evaluate the differential response to ractopamine of implanted, finishing steers and heifers. Treatments were steer vs. heifer and 0 vs. 200 mg/d ractopamine fed for the final 28 days. This study attempted to address some questions generated from the previous study, which were how serum and local tissue production of IGF-I are affected by ractopamine. Ractopamine had different effects on serum IGF-I between steers and heifers and numerically increased IGF-I mRNA abundance in longissimus and biceps femoris muscles. Additionally, ractopamine impacted protein turnover differently in different muscles and changed myosin heavy chain IIA expression. The effect of ractopamine on IGF-I warrants more research. These experiments aid in our understanding of the mode of action of ractopamine in cattle.

Enhancing the Proportions of Healthy Fatty Acids in Milk from Dairy Cows by Korie A.S. Nelson, Master of Science Utah State University, 2008 Major Professor: Randy Wiedmeier Department: Animal, Dairy, and Veterinary Sciences Twenty cows were used in a repeated measures, block design experiment for 9 wk to determine the effects of feeding partially ruminally inert calcium salts (Ca-salts) of fish oil (FO) and a general fatty acid (FA) supplement (EnerGII) at varying levels. The effects on cow health, milk components, composition of milk FA, and sensory evaluation of milk were evaluated. Cows in the 4 treatments were fed either a control diet of 57% forage and 43% concentrate mix with EnerGII fat supplement at 1.65% of diet DM (CTL) or EnerGII in basal diet was partially replaced with (a) 0.21% partially ruminally inert calcium salts (Ca-salts) of 71% fish oil (Ca-FO71) given at 0.41% DM (FH41); (b) 0.41% inert Ca-FO71 given at 0.83% DM (FH83); or (c) 0.83% inert Ca-FO 43% fish oil (Ca-FO43) given at 0.83% DM (FL). Cow health was not negatively affected by treatment diets. Treatment only significantly affected dry matter intake (DMI) and net energy of lactation (NEL), with FH83 having the lowest DMI. Week of trial significantly affected all milk components except protein percent, which did not change. Dry matter intake, milk yield, fat yield, fat percent, and protein yield demonstrated a net decrease over time. Lactose, solids, and somatic cell count all shared a net increase over time. iv Milk urea displayed no definitive trend over time. Content of conjugated linoleic acid (CLA) isomers C18:2 cis-9, trans-11 and trans-10, cis-12 combined over time was 0.54, 0.68, 1.18, and 0.82 g/100 g FA for CTL, FH41, FH83, and FL, respectively. Vaccenic acid (VA) C18:1 trans-11 content over time was 1.04, 1.51, 2.28, and 1.68 g/100 g FA; and total omega-3 FA content over time was 0.52, 0.76, 0.82, and 0.80 g/100 g FA for CTL, FH41, FH83, and FL, respectively. Eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) levels increased by as much as 6- and 2.7-fold, respectively, over CTL for the duration of the experiment. Although levels of EPA, DHA, VA, and CLA increased for treatments FH41, FH83, and FL over CTL, a trained sensory panel detected no difference in milk flavor between treatments with little or no intensity of off-flavors. Results suggest that feeding FO and EnerGII at varying levels enhanced CLA, VA, EPA, DHA, and total omega-3 FA in milk over the length of the experiment without negatively affecting cow health, milk composition, or flavor of milk.