Thesis (Ph. D.)--University of Missouri-Columbia, 1996. / Typescript. Vita. Includes bibliographical references (leaves 105-129). Also available on the Internet.

Thesis (Ph. D.)--University of Missouri-Columbia, 1996. / Typescript. Vita. Includes bibliographical references (leaves 105-129). Also available on the Internet.

Thesis (Ph. D.)--Ohio State University, 2004. / Title from first page of PDF file. Document formatted into pages; contains xiv,148 pages; also includes graphics Includes bibliographical references (p. 121-136). Available online via OhioLINK's ETD Center

Thesis (Ph.D.)--University of Missouri-Columbia, 2004. / Typescript. Vita. Includes bibliographical references (leaves 142-155). Also available on the Internet.

Thesis (Ph.D.)--University of Missouri-Columbia, 2004. / Typescript. Vita. Includes bibliographical references (leaves 142-155). Also available on the Internet.

M.Sc. / Various researchers have found that supplementing extremely high levels of dietary vitamin D₃ for a limited time prior to slaughter improved meat tenderness due to the increase in blood calcium levels caused by vitamin D, which play an important role in activating the calpain protease system. Vitamin D₃ is metabolised in the liver into 25-hydroxyvitamin D₃ , which controls calcium and phosphate homeostasis, a process regulated by parathyroid hormone. It is hypothesised that ultra-high vitamin D₃ supplementation should alleviate negative effects of beta-agonist supplementation (which reduces meat tenderness), but these levels might be toxic for human consumption. The aim of this study was to determine the levels of vitamin D₃ and its metabolites after feeding of high levels of vitamin D₃ to beef animals to alleviate the effects of beta-agonist supplementation in feedlot cattle and to determine the safety of tissues after ultra-high levels of supplementation of vitamin D₃ . In this study, 20 young steers received neither beta agonist nor vitamin D₃ (control, C), 20 animals each received zilpaterol hydrochloride (Z) and vitamin D₃ . Various levels of vitamin D₃ was administered (xM=x million units), for a given number (y) of days (yD) in some cases withdrawn (N) for a period of z days prior to slaughter (zN). Thus the following treatment groups were examined in this study: C, Z, Z3D7M, Z6D7M, Z6D7M7N and Z9D1M. Samples of liver, meat and fat were analysed for vitamin D₃ and 25-hydroxyvitamin D₃ . An HPLC method for quantification of vitamin D₃ and its metabolites was developed and used to quantify and compare vitamin D₃ and its metabolites from liver, meat and fat. Blood serum was analysed for calcium, phosphorus and parathyroid hormone. Serum calcium concentrations were analyzed using a colorimetric assay kit whereas plasma parathyroid hormone levels (PTH) were determined by an electrochemiluminescence immunoassay employing a sandwich test principle. Levels of vitamin D₃ and 25- hydroxyvitamin D₃ differed with the amount fed - levels in the meat were generally lower than the RDA. Vitamin D₃ was most abundant in liver, especially in the group supplemented with 7 million IU of vitamin D₃ for six days (Z6D7M), accumulating at an average level of 74 μg/100 g, followed by fat (8.39 μg/100 g accumulated vitamin D₃ ), which is higher than the average RDA. Vitamin D₃ supplementation resulted in significant lowering of the M. longissimus lumborum Warner-Bratzler shear force (WBS) and myofibril fragmentation (MFL). There were several positive and negative ix correlations between levels of 25-hydroxyvitamin D₃ and calcium, phosphate, parathyroid hormone and vitamin D₃ , WBS and MFL of M. longissimus lumborum and the muscle proteolytic degradation system (calpastatin, μ-calpain and mcalpain). Controversy remains regarding the upper limit (toxic level) of vitamin D₃ for human consumption. New studies indicate that the current RDA of vitamin D is too low for sufficient health benefits. Vitamin D₃ levels measured in this study were higher than the current RDA, but within the limit proposed by recent clinical studies. Vitamin D₃ as a tool for a meat tenderizer seems not providing reliable results because in this study the control group exhibited lower shear force than the treated groups who received vitamin D₃ zilpaterol supplementation. This is an indication that the tenderazation mechanism by vitamin D₃ still needs further elucidation before vitamin D₃ supplementation can confidently be used as a tool for meat tenderization.

Gas chromatography mass spectrometry (GCMS) and inductively coupled plasma mass spectrometry (ICPMS) were evaluated for the measurement of selenium (Se) and Se stable isotope ratios. GCMS and ICPMS were found to be accurate for quantitative Se analysis in biological matrices by isotope dilution using Se-78 and Se-76 as internal standards, respectively. A higher precision was obtained for ICPMS than GCMS enabling a smaller quantity of the tracer to be administered to subjects in labelling experiments. The isotopes of choice for metabolic tracers were Se-76 when sample analysis was by GCMS and Se-77 and Se-82 when analysis was by ICPMS. The influence of copper (Cu) on endogenous fecal Se excretion and true absorption of Se in nonlactating Holstein cows was examined by the use of Se stable isotopes as tracers. The method involved the application of conventional balance techniques in conjunction with isotopic enrichment of the body Se pools. Selenium in several tissues following oral and intravenous routes of isotope administration were evaluated as the precursors of endogenous fecal Se. Two cows fed a Se deficient diet (0.035 mg kg⁻¹) were administered 4 mg Se-76 orally, daily, for 5 d. After a 10-d equilibration period total collection of feces was made daily for two 5-d periods. The animals were then sacrificed and samples obtained from all major tissues and fluids. Se-7 6 enrichment (tracer/tracee mass percent, TTMP) in tissues was variable (< 0.56 - 13.4). However, enrichment was similar (9.8 - 12.9) in the tissues considered as potential contributors to endogenous fecal Se (serum, epithelium of the stomach, liver, bile, pancreas, small intestine and colon). Enrichment in serum and liver was used to calculate endogenous fecal Se. Apparent absorption of Se in the two cows was negative (-37 and -147 µg d⁻¹). Correction of apparent absorption for the fecal Se of endogenous origin gave a true Se absorption (% of intake) of 10 and 16%. The percentage of total fecal Se of endogenous origin was 23 and 36%. In two trials, 5 or 6 cows were assigned to one of two Cu-supplemented treatment diets: 0 mg kg⁻¹ or 17 mg kg⁻¹. The basal diet contained 0.19 mg Se kg⁻¹ and 13 mg Cu kg⁻¹. To each cow ~4.6 mg Se-77 and ~1.3 mg Se-82 were administered by oral and intravenous routes, respectively. After a 14-d equilibration period, total collection of feces and urine were made daily for two 5-d periods. Serum was collected on the first, third and fifth days of each period. Liver biopsies were taken 2 d following the completion of the balance periods. The estimates of endogenous fecal Se ( d⁻¹) from enrichment in the serum (256) and liver (235) following oral administration of the tracer and from enrichment in serum (241) following intravenous administration were not significantly different (P>0.05) but were higher than the estimate from the enrichment in liver (197) (P<0.05). No significant differences (P>0.05) were present when true absorption ( µg d⁻¹) was determined from enrichment in serum (290) or liver (268) following oral administration or from enrichment in serum (274) or liver (230) following intravenous administration. It was concluded the analysis of serum or liver with oral administration or the analysis of serum with intravenous administration of the tracer would provide reliable methods for estimation of endogenous fecal Se and true absorption. There was no effect of Cu on endogenous fecal Se excretion or true absorption of Se. Apparent and true absorption were 3.2 and 11%, respectively. Approximately 90% of the total Se excreted was in the feces, of which, 9.7% was of endogenous origin. The use of Se stable isotopes as metabolic tracers in dairy cattle provided a safe alternative to the use of radioactive tracers and enabled experiments requiring multi-isotopic enrichment to be performed. / Land and Food Systems, Faculty of / Graduate

Three experiments were conducted to study the sensitivity of the pH-stat (in vitro) method in the prediction of true digestibility (TD), as measured by amount of base added, of plant proteins, either alone or in the presence of specific additives (nitrogen-free mixture, vitamin mixture and/or mineral mixture) as part of a complete diet of plant proteins that had been subjected to various levels and forms of heating. The in vitro TD values were then compared with TD values obtained in. vivo (Wistar rats). In experiment 1, the effect of temperature (dry-heating at 80, 100, 120, 150, 180 and 240° C or autoclaving at 121° C) and time (30, 60, 120 and 240 minutes) of heat application on in vitro base consumption (BC) was measured in 3 grains (wheat, barley and sorghum) and whole defatted soybeans. The largest increase in BC measured by the pH-stat method was that of soybeans in response to 30 minutes of autoclaving. Dry heating had various effects on the BC by soybeans, depending upon temperature and time of application, but none of the treatments was as beneficial as autoclaving. Mild, dry-heating of grains at 80-120° C improved BC slightly. The improvement was most marked for wheat. Both dry-heating of grain at temperatures above 120° C and autoclaving reduced the BC significantly for all durations. In experiment 2, the effect of inclusion of non-protein dietary components (minerals, vitamins and a nitrogen-free mixture, singly and in combination) on in. vitro BC measured by the pH-stat method of wheat and fat-extracted soybeans (both proteins in the raw and autoclaved forms) was monitored. For the wheat treatments, the inclusion of a mineral mixture significantly (p<0.001>) increased digestibility. This effect was greatest with autoclaved wheat. It was concluded that, in general, the presence of minerals increased the rate of hydrolysis. With raw soybeans, the distinction between treatments was less well-defined. The treatments containing vitamin or nitrogen-free and mineral combination mixtures were digested to a significantly greater extent than the raw soybeans alone. With autoclaved soybeans, additives had no effect. This lack of response to additives may have been due to the rather large amount of base required by the autoclaved soybean protein alone. In experiment 3, a series of rat-feeding trials were conducted in conjunction with in. vitro digestions. Diets were fed to groups of Wistar rats to determine TD, Biological Value (BV), and Net Protein Utilization (NPU) in vivo. Although BV was measured it was not relevant for this work. Concurrently, the same diets were tested for in. vitro TD by the pH-stat method. Specific regression equations were developed for each protein-type tested, after it was determined that a much lower correlation coefficient was obtained when one general equation was utilized. The newly-developed equations followed the format y = a + bx, where y = TD (as a part of one), a = the y-intercept, b = slope of the function and x = ml 0.10N NaOH added during the 10-minute digestion. Regression equations, correlation coefficients (r) and standard errors for each regression (s) between in. vitro and in vivo true digestibility of proteins were as follows; Soybean, soybean (autoclaved), soybean/wheat combinations (n = 6) r = 0.93 TD = 0.7868 + 0.2175x s = 0.018 Sorghum (raw, autoclaved, 90° C, 120° C, 180° C dry-heated, steamed) (n = 6) r = 0.92 TD = 0.4575 + 1.8841x a = 0.058 Alfalfa pellets/hay in combination with either wheat or barley (n = 13) r = 0.91 TD = 0.3446 + 1.0356x s = 0.046Alfalfa hay and barley combinations (n = 5) r = 0.96 TD = 0.2360 + 1.3194x s = 0.048 Grains (19 barleys, 10 triticales, 6 sorghums, and 2 wheats) (n = 37) r = 0.74 TD = 0.7419 + 0.4759x s = 0.044 In general, it can be stated that the pH-stat method is a useful method for screening proteins for the effect of various treatments on digestibility. Damage due to abnormally severe processing conditions (i.e. heating) is readily detected by the pH-stat technique as indicated by a decrease in the amount of base consumed during enzymatic hydrolysis. / Land and Food Systems, Faculty of / Graduate

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