This study relates the species composition, numbers, and habits of a hole-nesting avifauna to its environment in successional stages of a coniferous forest in southwestern British Columbia. Emphasis is placed upon explaining an observed presence or absence of nest-site competition. In two breeding seasons, the hole-nesting avifauna was found to be low in numbers of both species and individuals. Most of these birds were able to excavate their own nesting cavities, and commonly did so, for which activity the habitat generally provided ample opportunity. As the species present often differed widely from one another in the type and placement of their preferred nest cavities, there was usually a surplus of different cavity types present. Secondary hole-nesters either concentrated their activities around the buildings in the nearby town, neglecting the more "natural" sites available; were not obligated to use cavities when nesting; or occurred in such low densities, and were so positioned in the available suitable habitat, as to suggest that nest-site competition had no effect upon the populations. Only scattered indications of nest-site competition were observed in wooded areas. Four species nested in crevices in buildings and in bird boxes in a small town, where their breeding population densities were much higher than in the surrounding countryside. Nest-sites were judged to be present in excess, and nest-site competition, observed infrequently, was so rare, and apparently without significant harmful effects, that it was judged to be of negligible importance as a population-regulating factor. The overall absence of nest-site competition is contributed to not only by the preferences of the species regarding their nest-sites, but also by the fact that the results of their habitat selection processes, and their living habits within these habitats, tend to keep them ecologically distinct. / Science, Faculty of / Zoology, Department of / Graduate

The effect of varying combinations of irradiation treatment, freezing procedures and duration of storage on the color of naturally and artificially pigmented egg yolk determined by two objective methods was studied. The relationship between the two methods of color evaluation was also determined. Naturally pigmented yolks were obtained from eggs laid by pullets of a single strain of Single Comb White Leghorn fed a standard diet. Artificially pigmented yolk was prepared by addition of either beta-carotene or canthaxanthin to the naturally pigmented material. Color of yolk was assessed: 1. On the basis of pigment concentration determined by absorbance of acetone extract and expressed as beta-carotene equivalent (BCE) and 2. On the basis of chromaticity coordinates (x,y), lightness (%Y), dominant wavelength (DWL) and excitation purity (EP) determined by reflectance spectrophotometry. Both irradiation dose (0, 0.5, 1.0 and 2.0 Mrad) and time of irradiation (before or after freezing) had significant effect on the chromaticity coordinates, BCE values and excitation purity of naturally and artificially pigmented yolk samples. Higher radiation doses and irradiation before freezing were associated with decreased chromaticity coordinates, BCE values and excitation purity. In artificially pigmented samples increases in irradiation dose and irradiation before freezing resulted in significant decreases in lightness. Samples frozen and stored at -10 F° had consistently higher mean chromaticity values and lower excitation purity than those at -35 F°. The temperature effect on BCE values was inconsistent among experiments. After 30 days storage mean x-values were lower and mean y-values were higher than after 10 days storage. These changes were associated with almost no change in DWL or EP. Nitrogen-packed samples had consistently lower BCE values than air-packed and this difference was significant in all but Experiment 1. No corresponding differences were found in chromaticity coordinates, lightness, DWL or EP. Correlation analyses revealed highly significant (P≤0.01) linear relationships between BCE and both chromaticity values and lightness ranging from + 0.09 to + 0.79. / Land and Food Systems, Faculty of / Graduate

In 1957, strains 3 and 4, two highly selected but unrelated strains of Single Comb White Leghorn chickens from Agriculture Canada's Animal Research Station at Ottawa were crossed to establish the Agassiz strain (strain 6). Further selection was imposed on strain 6 for improvements in hen-housed egg production (HHEP) based on part-records to 273 days and maintenance of egg weight, fertility, hatchability and viability. Data from 1957 to 1963 were analysed utilizing the SAS programs. There were no significant improvements in performance for HHEP, but egg weight, fertility, hatchability and viability were maintained. The lack of response to selection for HHEP was probably due to the following reasons: 1) too many traits were considered in the selection program at the same time, 2) negative genetic correlations existed among the selected traits, 3) strict adherence to a selection scheme was not practiced, 4) most of the traits under selection had low heritabilities, 5) the duration of the study was not long enough, and 6) the population size of strain 6 may not have been large enough. There was a significant decrease in body weight at 365 days (-4.33 ± 0.48, p < 0.0009). This decrease may be because of selection within full-sibs for more refined birds with better conformation as parents of the next generation. There were significant decreases in egg specific gravity at 225 and 450 days, and in Haugh units at 225 days, although Haugh units were increasing when measured at 450 days. The mean h²s for HHEP was 0.45, and the mean h²s for egg production to 273 days was 0.20 and the mean h²d for the same trait was 0.33. The mean h²s and h²d estimates for egg weight at 225 days were 0.60 and 0.50, respectively. The mean h²s and h²d for age at sexual maturity were 0.22 and 0.33, respectively, and those for body weight at 365 days were 0.53 and 0.62, respectively. The mean h²s and h²d for egg specific gravity at 225 were 0.64 and 0.33, respectively while those for Haugh units at 225 days were 0.57 and 0.68, respectively. These estimates were consistent with those found in the literature. The sctual selection differentials showed that selection was positive for egg production, while those for egg weight at 225 days were zero, and those for body weight at 365 days showed that selection was in the downward direction on the sires. / Land and Food Systems, Faculty of / Graduate

La viabilidad de los tratamientos con radiación ultravioleta (UV-C) a 254 nm como proceso no térmico para la conservación de ovoproductos líquidos fue evaluada desde el punto de vista de la eficiencia en la descontaminación y sus efectos en los atributos de calidad. Los estudios cinéticos sobre la inactivación de microorganismos inoculados y de los principales grupos de microorganismos alterantes sirvieron para discriminar los parámetros más relevantes del tratamiento con UV-C. Los estudios de vida útil sirvieron para evaluar las ventajas aportadas por esta tecnología frente a tratamientos térmicos tradicionales. Las fracciones de huevo (clara, yema y huevo entero) tratadas con UV-C fueron analizadas en cuanto a los cambios de pH, color, estabilidad de lípidos (TBARS, colesterol y valor de peróxidos), efectos en las proteínas (oxidación proteica, DSC, SDS-PAGE), propiedades reológicas (viscosidad dinámica, comportamiento de flujo, viscosidad en función de la temperatura), propiedades funcionales (emulsionantes y espumantes), composición nutricional (vitaminas y minerales), composición de componentes saludables (carotenoides), y cito-genotoxicologia. Finalmente, la aceptación sensorial de los ovoproductos líquidos tratados por UV-C y de productos preparados con ovoproductos líquidos tratados por UV-C (mayonesa, bizcocho y pudin) fueron evaluadas por medio de pruebas triangulares y afectivas. El tratamiento con UV-C demostró ser una excelente alternativa a la pasteurización térmica. En microorganismos inoculados, se demostró una reducción de 5 Log tanto para Gram(+) como para Gram(-) en un equipo comercial para tratamientos en régimen continuo (UVivatec�). En tandas, los resultados también mostraron decrecimientos importantes en el recuento de microorganismos inoculados, aunque serían necesarios tiempos largos de tratamiento para producir una descontaminación comparable a la pasteurización térmica. Los ovoproductos líquidos tratados con UV-C fueron estables durante 8 / Mendes De Souza, P. (2012). Study of short-wave ultraviolet treatments (UV-C) as a non-thermal preservation process for liquid egg products [Tesis doctoral no publicada]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/16696 / Palancia

The goal of this study was to determine if hatching synchrony occurs in loggerhead sea turtle nests and if it does, what mechanism(s) promote that synchrony. Synchrony may occur because oviposition takes place during a single evening, and because incubation temperatures within the nest show relatively little variation; thus, rates of embryonic development among the eggs are similar ("temporal synchrony hypothesis"). Alternatively, synchrony might be enhanced through embryo-to-embryo communication that stimulates and synchronizes development ("coordinated hatching hypothesis"). Experiments were designed to distinguish between these two hypotheses. I found that if only a few embryos survive, temporal synchrony occurs. However, if many embryos survive, the duration of incubation and hatching shortens, presumably because embryonic movements inside soft-shelled eggs are detected by and transmitted between eggs and stimulate development, expediting hatching synchrony. / Includes bibliography. / Thesis (M.S.)--Florida Atlantic University, 2020. / FAU Electronic Theses and Dissertations Collection

Under the expected warmer temperatures due to climate change, sea turtle embryos may be subjected to thermal conditions detrimental to nest success and hatchling quality; one trait which may be negatively affected is cognitive ability. In this study, loggerhead sea turtle eggs were acquired from Boca Raton, FL and lab incubated under two female-producing temperatures: an “optimal” temperature of 31°C and a sublethal temperature of 33°C. Cognitive ability of post-hatchlings, assessed via associative learning and reversal was investigated using a y-maze. The sublethal temperature decreased incubation duration, hatch success, hatchling growth rates and produced smaller hatchlings with significantly more scute anomalies. Hot hatchlings performed worse on the reversal, taking longer to train, and thus hint at an effect of incubation temperature on cognitive flexibility in loggerhead turtles. With temperatures rising on beaches in South Florida, this study provides evidence of further potential threats to hatchling quality and potentially even survival. / Includes bibliography. / Thesis (M.S.)--Florida Atlantic University, 2020. / FAU Electronic Theses and Dissertations Collection

Microbiological screening of antimicrobial residues in eggs needs special attention because of the high level of naturally occurring inhibitors contained in eggs which often lead to false positive results. However, it was discovered that heating egg samples at 800C for 10 minutes inactivated the inhibitors. The new bacteriological screening test for antimicrobial residues in eggs which was developed during this study, contains viable spores of Geobacillus stearothermophilus which are sensitive to antimicrobial residues including beta-lactams, tetracycline’s and macrolides. The new test method was validated based on the comparison with a reference method, namely the Kundrat micro-screening four-plate test,1 and published literature of another standard reference method, the Premi®Test. A preliminary trial was conducted on 36 hens that were given therapeutic oral doses of overthe- counter antimicrobials daily for seven days with one of eleven antimicrobials based on the manufacturer’s recommendations. Eggs were collected from the hens during and after treatment and tested for the presence or absence of antimicrobial residues. Several performance criteria and minimum detection concentrations were estimated and discussed. Some agreements and differences were found between the new and the reference tests with the new test being more sensitive to beta-lactams, tetracyclines and macrolides than the Kundrat and Premi®Test on the average. The use of florfenicol and norfloxacin in laying hens is banned and therefore there are no maximum residue limits (MRL) or published Premi®Test values. For meat, the MRL is 100mg/kg. It was therefore concluded that the new screening test could be used for routine screening of antimicrobial residues in eggs. A two seasonal survey was also conducted to determine the prevalence of antimicrobial residues in commercial chicken eggs in Tshwane area of Gauteng Province, South Africa. Although the season did not impact statistically on the antibiotic residues found in the eggs; eggs sold at the roadside (informal businesses), certain egg brands, and those sold at lower prices were found to be more likely to contain antibiotic residues than those obtained from formal outlets and at higher prices. Copyright / Dissertation (MSc)--University of Pretoria, 2011. / Production Animal Studies / unrestricted

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