A 130-d study was conducted with 24 363kg steers allotted to four diets containing .3 (basal), 1.4, 2.5 and 3.7% Mg, dry basis. An attempt was made to feed cattle on all treatments equal amounts of the basal diet, but steers fed the two high levels refused some feed. Grab fecal samples were collected during nine 10-d periods. Chromic oxide was used as a digesta marker. Jugular blood samples were taken on d 1, 5, 10, 20 and every 10 d thereafter. Steers were sacrificed at the end of the study for gross pathological and histological observations and tissue samples were taken for mineral analysis. Severe diarrhea was observed in steers fed the two higher Mg levels. Tubular strands of mucosal tissue were consistently voided in the feces of cattle fed these levels of Mg. Steers fed the two higher Mg levels became more lethargic as the study progressed. Fecal dry matter content and apparent dry matter digestibility decreased linearly (P<.01) with increasing dietary Mg. Weight losses for steers fed 1.4, 2.5, or 4.7% Mg were 5, 27 and 29 kg, respectively, during the study, compared to a weight gain of 9 kg for cattle fed .3% Mg (quadratic effect, P<.01). Apparent absorption of Mg generally increased with dietary Mg (P<.01), except between d 20 and 70 when it decreased (P<.01). Apparent absorption of Ca and P generally decreased with dietary Mg but effects on P absorption were not always significant. Increasing dietary Mg resulted in a linear elevation of serum and erythrocyte Mg (P<.01) and inorganic P (P<.05) and a linear decrease in serum Ca (P<.01). Plasma osmolality tended to be lowest in steers fed the highest dietary Mg. Serum parathyroid hormone was suppressed at the higher Mg intakes at 3 h but not at 9 h after feeding. Ruminal fluid pH increased as dietary Mg increased from .3 to 2.5%, then decreased (quadratic effect, P<.05). A linear increase in pH (P<.05) was recorded with increasing dietary Mg in digesta samples taken at slaughter from the lower ileum and large intestine. The Mg concentration in the liver, kidney, skeletal muscle and rib-bone and the P concentration in the skeletal muscle increased linearly (P<.05) with dietary Mg. Histologically, amorphous crystals were seen in the kidney tubules of all animals. Increasing dietary Mg in the steers caused a progressive degeneration of the rumen papillae epithelium. / Ph. D.

Masculinization of the female fetus by administration of androgens has been studied in domestic and many laboratory species. Research concerned with cattle has been based solely on neonatal examination of the genital structures; no studies have reported on postnatal growth and development of androgenized offspring. In the present study, pregnant cows were treated with l 7α-methyl-testosterone (MET, 250 mg/d, sq) from day 40 through 60 of gestation to induce virilization of female fetuses. Control cows received no treatment. At parturition, the phenotypic characteristics of each calf were recorded, including birth weight, ano-genital distance and the appearance of the external genitalia. Calves were weighed every 28 days, and the effects of sex and age on body weight were determined. Blood serum was obtained twice weekly from female calves beginning at ≃230 days of age. Serum was analyzed for progesterone (P₄) concentration by radioimmunoassay and the P₄ profiles were used to estimate the age at puberty and estrous cycle lengths. At 4, 8 and 12 months of age blood samples were collected every 15 min for 12 h from three male, female and androgenized female calves. Serum was analyzed for growth hormone (GH), prolactin (PRL) and thyroxine (T₄) concentrations by radioimmunoassay. Visual examination of female calves born after MET exposure revealed that no external vulval opening was present; a penis, prepuce and scrotum had developed and gonads were not palpable in the scrotum. Mean birth weights were similar among male, untreated female and androgenized female calves, whereas weanling and yearling weights were greater (P < .07) in males and androgenized females than in untreated females. Androgen exposure did not affect the initiation or length of estrous cycles in female calves, however, puberty occurred at an earlier age (P < .05) compared with untreated heifers. Concentrations of GH in serum from androgenized female calves were generally lower than both males and untreated females, whereas concentrations of PRL and T₄ were similar to those of control female calves. / Master of Science

Three experiments compared ruminal, physiological, and performance responses of beef steers consuming hay ad libitum and receiving grain-based supplements with (CAM) or without (CO) inclusion of camelina meal. In Exp. 1, 9 steers fitted with ruminal cannulas received CAM (2.04 kg of DM/d) or CO (2.20 kg of DM/d). Steers receiving CAM had reduced (P = 0.01) total DMI and tended to have reduced (P = 0.10) forage DMI compared to CO. No treatment effects were detected (P ≥ 0.35) for ruminal hay degradability parameters. In Exp. 2, 14 steers receiving CAM (1.52 kg of DM/d) or CO (1.65 kg of DM/d) were assigned to corticotropin-releasing hormone (CRH; 0.1 μg/kg of BW) and thyrotropin-releasing hormone (TRH; 0.33 μg/kg of BW) challenges. Steers receiving CAM had greater (P < 0.05) serum concentrations of PUFA compared to CO prior to challenges. Upon CRH infusion, mean plasma ceruloplasmin concentrations increased at a lesser rate in CAM compared with CO (P < 0.01). Upon TRH infusion, no treatment effects were detected (P ≥ 0.55) for serum TSH, T₃, and T₄. In Exp. 3, 60 steers were allocated to 20 drylot pens. Pens were randomly assigned to receive CAM (2.04 kg of DM/steer daily) or CO (2.20 kg of DM/steer daily) during preconditioning (PC; d -28 to 0). On the morning of d 0, steers were transported for 24 h. Upon arrival from transport on d 1, pens were randomly assigned to receive, in a 2 x 2 factorial arrangement, CAM or CO during feedlot receiving (FR; d 1 to 29). During PC, CAM had reduced (P < 0.01) forage and total DMI, and tended to have reduced (P = 0.10) ADG compared to CO. Plasma linolenic acid concentrations increased during PC for CAM, but not for CO (P = 0.02). Steers that received CAM during FR had greater (P < 0.05) mean plasma concentrations of PUFA, and reduced mean rectal temperature and concentrations of haptoglobin and ceruloplasmin during FR compared to CO. Therefore, camelina supplementation reduced forage and total DMI, did not alter thyroid gland function, increased PUFA concentrations in blood, and attenuated the acute-phase protein reaction elicited by neuroendocrine stress responses. In conclusion, camelina meal is a feasible ingredient to reduce stress-induced inflammatory reactions and potentially promote cattle welfare and productivity in beef operations. / Graduation date: 2012

Perennial ryegrass (PRG, Lolium perenne) is a hardy cool-season grass that is infected with the endophytic fungus Neotyphodium lolii, which enables the plant to be insect repellant and drought resistant, lowering the use of insecticides and fertilizers. However, this fungus produces the compound lolitrem B (LB, m/z 686.4) which causes the tremorgenic neurotoxicity syndrome 'ryegrass staggers' in livestock consuming forage which contains <2000 ppb LB. Ergovaline (EV, m/z 534) is a vasoconstrictor normally associated with tall fescue (Festuca arudinacea), but has also been found in endophyte-infected PRG. Past research has shown a strong linear correlation between levels of LB and EV in PRG. The purpose of this study was to examine the linear relationship between EV and LB in feces and determine common metabolites. To accomplish this, four groups of steers (n=6/group) consumed endophyte- infected PRG over 70 days consumed the following averages of LB and EV: group I 2254ppb LB/633 ppb EV; group II 1554ppb LB/ 373ppb EV, group III 1011ppb LB/259ppb EV, and group IV 246ppb LB/<100ppb EV. Group I in week 4 was inadvertently given a washout period at which time the steers consumed the amount of LB and EV given to group IV (control). Both feed and feces samples were extracted using difference solid phase extraction methods and quantified by HPLC-fluorescence for LB and EV. Concentrations of EV and LB obtained through HPLC-fluorescence in both PRG and feces showed a linear relationship. Additional screening for metabolites was conducted LC-MS/MS and showed possible oxidation and reduction metabolites for both toxins. / Graduation date: 2013