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Call number: LD2668 .T4 1978 K536 / Master of Science

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>

We investigated the molecular epidemiology, differential susceptibility to infection and disease, pathogenesis, diagnosis and treatment of avian mycobacteriosis in captive ringneck doves (Streptopelia risoria) and in the endangered white-winged duck (Cairina scutulata), both naturally infected with Mycobacterium a. avium. Our studies in doves demonstrated lower susceptibility to infection and less severity of lesions in the white color morph compared with the non-white. Genetic mechanisms of immunity to mycobacteriosis may be contributing or determining these differences. Given that the genes that code for white coloration are sex linked in birds, it is very likely that the gene or genes modulating this different immune response to M. a. avium infection in these doves could be associated to these loci or at least located in the same sexual (Z) chromosome, as the association with white color suggest. In the same birds, spleen biopsies followed by liver biopsies had the greatest potential for the diagnosis of mycobacteriosis by the demonstration of acid-fast organisms. Additional culturing of spleen or liver biopsies significantly increased the diagnosis of mycobacteriosis. The use of polymerase chain reaction (PCR) was the less sensitive techniques. Uneven distribution and low number of organisms in the liver, spleen and bone marrow may have contributed with the low diagnostic value of PCR. In a second group of sixteen doves with mycobacteriosis from the same flock, the combination of azithromycine, ethambutol and rifampin for 180 days was well tolerated but failed to cure them. Furthermore, this study demonstrated the inefficacy of liver biopsy to evaluate treatment as well the presence of antibiotic resistance in two isolates. These results highlight that erradication of mycobacteriosis in birds is not easy to achieve. Together with the possible emergence of antibiotic resistance in potentially zoonotic mycobacteria our results suggest that the treatment of mycobacteriosis in birds should not be recommended. Finally, the last study shows that white-winged ducks are highly susceptible to at least two sequevars of M. a. avium and that mycobacteriosis is a major threat to the ex situ conservation program. The minimal heterozygosis previously shown in these ducks could be contributing to this apparently ineffective immune response.

Thesis (M.S. - Renewable Natural Resources)--University of Arizona, 1982. / Includes bibliographical references (leaves 72-78).

Thesis (Ph. D.)--University of Missouri-Columbia, 1996. / Typescript. Vita. Includes bibliographical references (leaves 123-141). Also available on the Internet.

Thesis (Ph. D.)--University of Missouri-Columbia, 1996. / Typescript. Vita. Includes bibliographical references (leaves 123-141). Also available on the Internet.

Conservation efforts to increase duck production have led the United States Fish and Wildlife Service to restore grasslands with multi-species (3-5) mixtures of cool season vegetation often termed dense nesting cover (DNC). The effectiveness of DNC to increase duck production has been variable, and maintenance of the cover type is expensive. In an effort to decrease the costs of maintaining DNC and support a more diverse community of wildlife, restoration of multi-species (16-32) plantings of native plants has been explored. Understanding the mechanisms of nest site selection for nesting ducks within these plantings is important in estimating the efficiency of this cover at providing duck nesting habitat and determining appropriate management techniques. I investigated the vegetation characteristics between the 2 aforementioned cover types in the prairie pothole region of North Dakota, USA to see if native plantings provide the same vegetative structure to nesting hens as DNC. I also determined the nest density and nest success of upland nesting waterfowl in the cover types to determine if restored native plantings are providing the same nesting opportunity as DNC. Within each cover type I identified vegetation characteristics at nest sites of the 5 most common nesting species and compared them to random locations and within species to identify species specific factors in nest site selection. I located 3,524 nests (1,313 in restored-native vegetation and 2,211 in DNC) of 8 species in 2010-11. Native plantings had an average of 6.17 (SE = 1.61) nests/ha while DNC had an average of 6.71 (0.96) nests/ha. Nest densities were not different between cover types for the 5 most common nesting species. In 2010, nest success differed between cover types with restored-native plantings having 48.36% (SE = 2.4) and DNC having 42.43% (2.1) success. In 2011, restored-native planting success dropped considerably to 13.92% (1.7) while DNC success was similar to 2010 at 37.10% (1.7) The variability in nest success appeared to be impacted by late season success, as native plantings had similar success early in the nesting season, but much lower success later in the nesting season in both years. Vegetation data indicated no structural difference between cover types in 2010; however, a difference was detected during the late sampling period in 2011, with native plantings having shorter vegetation at random locations than DNC during this sampling period. In general ducks selected nest sites with greater leaf litter and denser, taller cover compared to random sites, however, vegetation density and height selection varied among species. Gadwall and mallards selected the tallest, densest vegetation, with northern pintail, blue-winged teal, and northern shovelers selecting vegetation of intermediate height and density. My results indicate native plantings are able to support similar densities of nests, but have great variability in nest success from year to year. In years with low nest success, native plantings may create an ecological sink as hens were not able to identify low quality patches and nested in similar densities despite lower success.

Plasma catecholamines have been measured in chronically adrenalectomised (ADX) ducks, in chronically adrenal denervated ducks (DNX), in their respective sham-operated controls (SH-adx, SH-dnx) as well as in intact ducks after 3 minutes forced submergence. The results showed that 100% of the plasma Epinephrine (EP) and 40 to 80% of plasma Norepinephrine (NE) released during the dive came from the adrenal glands. 20 to 60% of plasma NE came from endings of the autonomic vascular sympathetic nerves which are strongly stimulated during diving. Adrenal catecholamines were released by nerve activation only; non neural mechanisms did not play any role in their release. Maximum dive times (MDT) in chronically adrenalectomised ducks (ADX: 5 min. 19 ± 20 sec.) and in chronically adrenal denervated ducks (DNX: 7 min. 10 ± 13 sec.) were significantly lower than in sham-operated controls (respectively SH-adx: 9 min. 58 ± 45 sec., SH-dnx: 12 min. 10 ± 28 sec). Venous infusion of catecholamines in ADX and DNX during the dive increased MDT: MDT of DNX ducks perfused with catecholamines (9 min. 46 ± 20 sec.) were significantly higher than in DNX perfused with saline (7 min. 21 ± 17 sec.), but did not reach the MDT observed in the SH-dnx: other adrenal products must be involved. Diving heart rates of ADX and DNX (at 4 min. dive respectively: 62 ± 16 and 31 ± 2 beats/min.) were significantly higher than in their sham-operated controls (23 ± 3 and 17 ± 2 beats/min.) . Blood pressure during the dive was signifi- cantly lower in ADX and DNX (at 4 min. dive respectively: 93 ± 8 and 98 ± 4 mmHg) compared with their sham-operated controls (131 ± 12 and 118 ± 6 mmHg). Infusion of catecholamines in DNX raised blood pressure towards SH-dnx values, but there was no change in heart rate. PaO₂, CaO₂, pHa and lactate levels in DNX (respectively: 42 ± 2 mmHg, 4.5 ± 0.8 ml 02 /100ml blood, 7.233 ± 0.016, 3.1 + 0.3 mM) were significantly lower than in SH-dnx after 5 minutes submergence (53 ± 1 mmHg, 6.8 ± 0.4 ml 02 /100 ml blood, 7.301 ± 0.007, 4.8 + 0.4 mM). There was also a significant increase of plasma N⁺ (+ 5.4 ± 1.7 mEq/L) in SH-dnx after 5 minutes submergence, but this was not the case in DNX where it was K⁺ (+ 1.1 ± 0.4 mEq/L) which increased. This suggested that adrenal catecholamines increase tolerance to underwater submersion by enhancing peripheral vasoconstriction, thus preserving the O₂ stores for the heart and brain. Moreover, they may affect the acid-base equilibrium during diving by increasing the activity of the Na⁺K⁺ pump and may also have a direct effect on the rate of glycogenolysis. Preventing the actions of catecholamines on the heart by injecting beta-blocker during forced submersion did not decrease MDT; however the cardiovascular response was markedly affected. During beta-blockade, diving heart rate rose steadily from 24 ± 6 beats/minute after 2 minutes to 52 ± 8 beats/minute after 6 minutes diving. In contrast, heart rates remained close to the levels reached at 2 minutes (17 ± 3 and 19 ± 4 beats/minute) throughout the control dives. Perfusion pressure and blood flow have been recorded simultaneously in both hind limbs of ducks. One leg was perfused with different blood mixtures devoid of catecholamines (Test leg) and compared with the other, perfused with the ducks'own blood (autoperfused leg). This showed that hyper-capnia has a depressant effect on the neural component of the peripheral vasoconstriction. Perfusion of test legs with hypoxic-hypercapnic blood to which catecholamines were added, showed that circulating catecholamines are needed to increase peripheral vasoconstriction during diving. In summary, during forced submergence circulating catecholamines, released mainly by the adrenal glands, compensate for the depressant action of hypercapnia on the neural component of peripheral vasoconstriction. Maintenance of this peripheral vasoconstriction during forced diving ensures that O₂ stores are not wasted on peripheral tissues, and this explains how MDT is prolonged. / Science, Faculty of / Zoology, Department of / Graduate

Ruddy Ducks in the Chilcotin parklands of British Columbia nest in late June, July and early August, later than most other waterfowl species breeding in southwestern British Columbia, Canada. This thesis considers factors that may affect the timing of breeding in Ruddy Ducks by comparing Ruddy Ducks to Barrow's Goldeneye and Bufflehead (species that breed early but do not renest) and to American Coot (a species that breeds early and is able to renest). These factors include predation, flooding and desertion of nests, feeding behavior of ducklings, abundance of food, availability of green vegetation and fluctuations in temperature. Possible advantages of late breeding include reduced nest predation and higher ambient temperature during incubation. Longer dive durations and more frequent feeding and resting by Ruddy ducklings may enable ducklings to maximize energy for growth. Reduced nest flooding late in the season, dependence on green vegetation for nesting and greater abundance of food for young in summer were not demonstrated by this study. Therefore, these factors apparently do not explain the timing of breeding in Ruddy Ducks in southwestern British Columbia. Despite insufficient time to renest and shorter time for ducklings to mature before ponds freeze, the average number of 2B age class young produced per pair of Ruddy Ducks was similar to that of American Coots. Forty percent of nesting Ruddy females did not hatch any young, whereas almost all nesting Coot females successfully hatched young; however, survival of Ruddy ducklings to 2B age class (four weeks old) was higher than that of American Coots, Barrow's Goldeneye and Bufflehead. / Science, Faculty of / Zoology, Department of / Graduate