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published_or_final_version / Physics / Master / Master of Science

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Doctor of Philosophy / Department of Animal Sciences and Industry / James S. Drouillard / Four studies evaluated effects of mineral supplementation on feedlot performance, carcass characteristics and ruminal fermentation of finishing cattle. Study 1 supplemented 0 or 3.3 g/d yeast combined with Cr propionate to steers separated into light and heavy groups. No treatment x weight group interactions were observed for ADG, DMI, final BW, carcass traits, or plasma glucose of lactate concentrations (P ≥ 0.06). A treatment x weight group interaction was observed for G:F (P = 0.03). In study 2, steers were supplemented 60 or 300 mg Zn/kg DM with or without zilpaterol hydrochloride (ZH). No interactions or effects of Zn or ZH were observed for IGF-1, plasma glucose, or lactate concentrations (P > 0.05). Plasma urea nitrogen (PUN) concentration decreased with ZH (P < 0.01). No interactions or effects of Zn or ZH were detected for ADG, DMI, final BW, G:F, and carcass traits were minimally affected (P ≥ 0.05). Study 3 evaluated effects of supplementing 30 or 100 mg Zn/kg DM (30 or 100Zn) with and without ractopamine hydrochloride (RH; 200 mg/d). No interactions or effects of Zn were observed for feedlot performance or PUN (P ≥ 0.07). Final BW, ADG, and HCW increased when heifers were fed RH (P ≤ 0.02). Zinc x RH interactions were observed for LM area and yield grade (P ≤ 0.01), but other carcass traits were not affected (P ≥ 0.08). In study 4, heifers were supplemented 0, 30, 60, or 90 mg Zn/kg DM. Zinc supplementation did not affect final BW, ADG, or DMI (P ≥ 0.07), but G:F increased linearly (P = 0.02). Carcass traits were not affected by Zn supplementation (P ≥ 0.07). Effects of in vitro Zn titration (0, 30, 60, 60, 90, 120, or 150 mg/kg Zn) were evaluated using ground corn and soybean meal as substrate. In vitro fermentation was not affected by added Zn (P ≥ 0.05). These studies suggest Cr and Zn supplementation minimally affected carcass traits, but Zn supplementation up to 60 mg/kg improved feed efficiency with minimal impact on ruminal fermentation. Supplementing increased Zn concentrations may alter fat and muscle deposition when fed with RH.

M.Com. (Economics) / Please refer to full text to view abstract

D.Sc. / Please refer to full text to view abstract

A dissertation submitted to the Faculty of Science, University of the Witwatersrand, Johannesburg, in fulfilment of the requirements for the degree of Master of Science WITS University, Johannesburg, 2013 / Occurring parallel to the developments in imprinting technology are magnetic materials which are being applied increasingly in environmental remediation, medicine, biotechnology and many other fields. Combining the imprinting effects of the polymer and nano magnetic particles yields composite materials which are both selective to the template and magneto responsive for easy polymer removal from aqueous solutions. In this study, magnetic ion imprinted polymers with high recognition for uranyl ion (UO2 2+) in the presence of competing ions were synthesized by bulk and precipitation polymerizations. The uranyl template was removed from the magnetic polymer matric by 1M HCl and 1M NaHCO3 leachants to form cavities which were complimentary in shape and size to the template. Full characterization of the magnetite and magnetic polymers was achieved by use of the following characterization techniques: Raman spectroscopy (RS), Transmission electron microscopy (TEM), Energy dispersive spectrometry (EDS), Powder X-ray diffraction (PXRD) analysis, Brunauer, Emmett and Teller (BET) analysis, Ultraviolet visible (UV-vis) spectroscopy, Fourier-transform infrared (FTIR), Thermo-gravimetric analysis (TGA), Carbon, hydrogen, nitrogen and sulphur (CHNS) analysis, Diffuse reflectance spectroscopy (DRS) and Atomic force microscopy (AFM). Parameters which were optimized included sample pH, which gave an optimum value of 4. Magnetic IIP and NIP amounts which gave maximum adsorption capacities were found to be 50 mg for both of these adsorbents. The optimum contact time was found to be 45 minutes. The performance of all magnetic ion imprinted polymers (IIPs) was expectedly superior to that of the corresponding non imprinted polymers (NIPs) in all adsorption studies. The first rate constant (k1) and correlation coefficient (R2) values evaluated for the pseudo first order were found to be between 0.048-0.093 min-1 and 0.602-0.991 min-1, respectively. For the pseudo second order, second rate constant (k2) and correlation coefficient (R2) were found to be between 0.273- 0.678 and 0.9811-0.9992, respectively. The selectivity order observed was as follows: UO2 2+ > Fe3+ > Pb2+ > Ni2+ > Mg2+. The magnetic polymers selective to Cr(VI) were also synthesized and were leached with HCl to remove the template. The synthesized Cr(VI) magnetic polymers, the optimum pH obtained was 4 for both the magnetic IIP and the corresponding NIP. The amount of the adsorbent which gave the maximum adsorption was determined to be 20 and 65 mg for the magnetic IIP and NIP, respectively. A Cr(VI) concentration which was adsorbed maximally was from 5 mg L-1 which was therefore taken as the optimum. The maximum adsorption capacities for the magnetic polymers were 6.20 and 1.87 mg g-1 for the magnetic IIP and NIP, respectively. The optimum time for the adsorption of the Cr(VI) analyte was determined as 40 minutes. Investigation of the order of selectivity of anions followed the trend: Cr2O7 2- SO4 2- F- NO3- -.

Remediation of heavy metals from industrial effluents and ground water sources poses a significant challenge. Hexavalent chromium is one such heavy metal, prevalent in industrial wastewaters, which has been proven to be toxic to humans and other living organisms. Most of the conventional methods available for dealing with chromium are either cost prohibitive or generate secondary effluents which are difficult to deal with. The idea of bioremediation has gained much momentum over the last few decades because of its potential low cost and minimum impact on the environment. This study explored the potential for hexavalent chromium bioremediation using a synthetic cationic biopolymer alpha-poly-l-lysine (alpha-PLL) as a biosorbent. In the present research work, equilibrium batch studies were performed in a specially designed dialysis apparatus to obtain preliminary information about the adsorption capacity of the polymer. Metal uptake by the polymer was found to be maximum when the pH of chromium solution (pH 4.6) and that of poly-lysine (pH 5.7) was not changed at the beginning of the experiment. Applying the Langmuir adsorption isotherm model showed that alpha-PLL has a maximum uptake capacity of 42.2 microgram Cr/mg alpha-PLL, and a binding constant of 1.2 microgram/mL +/- 10%. The metal uptake performance of the polymer was also evaluated in a Polymer Enhanced Diafiltration (PEDF) system. The polymer-metal complex was retained and concentrated by the PEDF set up using a tangential flow filtration membrane, while the clean filtrate flowed through. When 3.4 L of 10 mg/L chromium solution in the Cr2O72- form was processed using 300 mL of 2 gm/L PLL, the concentration of chromium in the permeate reached a maximum of 0.79 mg/L. When 30 mg/L chromium solution was used, 2 L could be processed using 300 mL of 2gm/L PLL, and 7.8 mg/L chromium could be detected in the permeate in the end.