Mycotoxins are feed contaminants that are a major problem in the livestock industry because of their prevalence in feedstuffs and the difficulty of removing them. They can cause a wide range of issues at varying levels of exposure. Each species is affected by different mycotoxins and at different levels. Pigs are more susceptible to deoxynivalenol (DON), whereas ducks are more susceptible to aflatoxin.<br> Effects of mycotoxin contamination on animal performance are not fully understood. Therefore, the two experiments described in this thesis were conducted to determine the response of pigs and ducks to consumption of feed contaminated with DON and aflatoxin, respectively. In the first experiment, the effect of a mycotoxin binder on duck feeds contaminated with aflatoxin was examined. One-day-old male Pekin ducks (n=360) were randomly divided into four groups; each group had 6 replicate pens with 15 ducks per replicate pen. The positive control (PC) group was fed a diet that was free of aflatoxin B1, the negative control (NC) group was fed a diet that contained >75ppb of aflatoxin without a binder, the negative control with low binder (NC + 0.5) group was fed a diet that contained >75ppb of aflatoxin and 0.5 kg/ton of the binder, the negative control with high binder (NC + 1.0) group was fed a diet that contained >75ppb of aflatoxin and 1.0 kg/ton of the binder. The diets were fed in two phases, days 0-14 (phase 1) and 15-35 (phase 2). The results showed that during early phase 2, NC + 0.5 resulted in a higher rate of weight gain compared to NC (P<0.05); 2) NC + 0.5 ducks had higher feather quality than both NC and PC (P<0.05); 3) NC had higher relative liver weights (P<0.05); 4) blood glucose was higher in NC + 0.5 ducks (P<0.05); and 5) PC ducks had higher serum protein levels in the blood (P<0.05).<br> In the second study, effect of the same mycotoxin binder, used in the duck study, was examined in pigs fed diets contaminated with DON. A total of 128 pigs (Duroc × Landrace × Yorkshire, (1:1 barrows and gilts, aged 42 d) were randomly assigned to 4 treatments, 8 replicate pens with 4 pigs per. The treatments were DON, DON + liver protectant (1 kg/ton), DON + mycotoxin binder (0.5 kg/ton), or DON + liver protectant and mycotoxin binder. The study lasted 28 days and body weights (BW), feed intake (FI), and blood samples were taken on days 14 and 28. Body weights and feed intake were taken and used to calculate gain:feed (G:F). Aspartate aminotransferase (AST) and alanine aminotransferase (ALT) were measured in the blood serum. BW, FI, and G:F were not significantly different at any point during the study. AST levels were significantly reduced (P < 0.05) on day 14 in pigs fed the liver protectant but were not significantly different day 28.<br> In summary, effects of the use of mycotoxin binders in feed can be highly variable. This depends on the type of mycotoxin present in the feed, the amount of mycotoxin, and the species fed the diet. In the present study, the mycotoxin binder did not have an impact on the feed efficiency of the ducks or pigs. Effects of additional binders need to be evaluated for their effectiveness in mitigating the negative effects of mycotoxins.<br><br>

No description available.

Contact Lens Acute Red Eye (CLARE) and Infiltrative Keratitis (IK) are inflammatory responses of the eye associated with extended wear of soft contact lenses. Bacterial colonization of contact lenses with Gram-negative bacteria such as Pseudomonas aeruginosa is an important risk factor for the development of these adverse responses. Strategies that control the bacterial colonization of contact lenses may help prevent the occurrence of adverse responses. This thesis aimed to develop an animal model of CLARE/IK to test this hypothesis and to test the effectiveness of contact lenses containing antimicrobial compounds, namely silver and furanone compounds, in controlling corneal inflammation caused by Pseudomonas aeruginosa. A guinea pig model of contact lens wear was developed for the study and it was observed that the ocular responses to contact lens wear in the guinea pig were similar to those seen in human eyes wearing contact lenses. Also, three different models for CLARE/IK were developed and tested in the guinea pig eye. The pathological features of CLARE/IK in the guinea pig were virtually identical to those observed in human eyes. Bacterial contamination of contact lenses was confirmed to be a major risk factor for the development of CLARE/IK. Contact lenses containing nano-particles of silver demonstrated very good antibacterial activity against Pseudomonas aeruginosa in-vitro. The silver lenses were able to control the development of CLARE/IK responses in one of the models for CLARE/IK. Silver lenses might be most effective if used to prevent the establishment of a biofilm of bacteria on a lens such as might occur during storage in a contact lens case. Contact lenses were coated with different concentrations of the furanone compounds by physical adsorption and demonstrated good antibacterial activity at higher concentrations. However these concentrations were cytotoxic in-vitro and lower concentrations of furanones did not possess adequate antibacterial activity to control CLARE/IK responses in-vivo. This thesis has successfully demonstrated that guinea pigs can be used to test the effects of extended wear of contact lenses and developed models to test the pathogenesis of adverse responses such as CLARE/IK. The CLARE/IK models developed could be used to further our understanding of the pathogenesis of these inflammatory conditions and explore the activity of other antimicrobials.

Optimal nutritional management of growing pigs is constrained by lack of quantitative information on the response of animals between 30 and 110 kg live weight to dietary energy content. Under 'ideal' conditions modern genotypes appear to adjust feed intake to maintain a constant DE intake over a much wider range of dietary energy concentrations than previously thought (Mullan et al, 1998). However, under commercial pen conditions, voluntary feed intake is lower, pigs respond in terms of both growth rate and feed conversion to dietary DE density considerably above the levels currently thought to maximise biological and economic responses. The present study was designed to provide information on the response of growing pigs to dietary energy content under ideal and commercial housing conditions for two growth periods 30-60kg liveweight and 60-100kg liveweight. The results of the pigs kept under individual (ideal) housed conditions were consistent with the literature in that they adjusted their voluntary feed intake with digestible energy density to maintain a constant energy intake. The results of the pigs kept in groups (commercial) housing conditions tended to increase their daily energy intake as the energy density of the feed increased. This increase in energy intake improved the growth rate of the pigs and increased the fat deposition of those pigs. Economic analysis of the experiments involving pigs in groups indicates that formulating diets to a least cost per megajoule of digestible energy is not the most profitable point to set the digestible energy density. Modelling programs need to be used to determine where the least cost per unit of growth of the pig occurs. This is the most economical digestible energy density to formulate too. This will have major impact on the cost of production of piggery operations as the cost of energy is the single most important parameter in the cost of producing a pig.

Denna uppsats sammanställer de finanspolitiska åtgärderna som genomförs i Portugal, Irland,Grekland och Spanien. Baserat på tidigare forskning diskuteras hur finanspolitiken bör utformas för att ge en så liten negativ effekt som möjligt på ekonomisk tillväxt. I den aktuella situationen har Portugal, Irland, Grekland och Spanien gemensam valuta vilket medför att länderna inte kan använda penningpolitiken för att påverka ekonomin och länderna kan inte heller förlita sig på att förändringar av växelkursen kan dämpa en eventuell negativ effekt på BNP. Dessutom diskuteras skuldutvecklingen i samtliga länder under olika förutsättningar, och beroende på hur åtstramningarna faller ut, för att se hur statsskulden påverkas. Uppsatsen kommer fram till att de finanspolitiska åtstramningarna troligtvis inte kommer att leda till expansiva effekter. Om åtstramningarna inte är tillräckliga för att skapa en hållbar utveckling av statsskulden, till exempel på grund av att de negativa effekterna på BNP blir större än väntat, finns egentligen bara två alternativ. Antingen tvingas länderna förhandla med långivarna om nedskrivning av skulderna eller så får länderna lämna eurosamarbetet.

Thesis (Ph. D.)--University of Hong Kong, 2001. / Includes bibliographical references (leaves 72-104).

Thesis (M. Phil.)--University of Hong Kong, 1980. / Typescript.

Thesis (M. Phil.)--University of Hong Kong, 1983.

Thesis--M. Phil., University of Hong Kong, 1980.

published_or_final_version / Anatomy / Master / Master of Philosophy