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

Native fowl populations in South Africa were characterized genetically and phenotypically. Four South African native populations, two dual-purpose breeds, and two populations from Mozambique and Botswana were included for genetic analysis. For phenotypic characterization, two commercial lines were also included as a benchmark. Twenty-three micro satellite markers were selected and tested to obtain genetic data for estimation of genetic variability and distance. Growth (weight gain) and egg production were included for phenotypic characterization. A relatively high (53% ¬64%) genetic variation was found among the populations, which suggests conservation as a genetic resource for future use. The lowest genetic variation (53%) was found for the Koekoek and Australorp populations, which are the two populations that were subjected to formal selection, while the highest variation was observed in the Naked Neck population (64%). The New Hampshire has often been included in upgrading programs and this is evident from the close relationship with both the Lebowa- Venda and Naked Neck fowls. Phenotypic trials indicated significant differences among the populations included for growth, carcass and egg production traits. The Koekoek and New Hampshire populations had the best performance for egg production and growth (weight gain) in the study. Genetic and phenotypic differences indicate that the populations can be distinguished as different breeds or groups of fowl. The results of this study may contribute to selection for improved performance for household food production, as well as conservation of the populations as a genetic resource. / Thesis (PhD)--University of Pretoria, 2001. / Animal and Wildlife Sciences / unrestricted

MSCAGR (Animal Science) / Department of Animal Science / The aim of the study was to investigate the effects of feed withdrawal and strain on laying performance and egg quality of White and Brown Hy-line layers. Fifty four hens for each strain (White Hy-Line and Brown Hy-line) aged 18 weeks (point of laying stage) were used in the investigation. Feed withdrawal had no effect (P>0.05) on laying performance, mortality rate, egg internal and external quality, but significantly affected (P<0.01) average feed intake, body weight, small and extra-large eggs percentages. Hens under ad libitum consumed more feed than hens under four hours and eight hours feed withdrawal. High body weight was observed on ad libitum fed hens, intermediate on eight hours feed withdrawn hens and lower at four hours feed withdrawn hens. High percentage of small graded eggs was observed on four hours feed withdrawn hens, intermediate on eight hours feed withdrawn hens and lower on ad libitum fed hens. High percentage of extra-large graded eggs was observed on ad libitum fed hens, intermediate on eight hours feed withdrawn hens and lower four hours feed withdrawn hens. Strain had a significant effect on average egg weight, median egg weight, albumen weight, extra-small, small, medium and large graded eggs percentages (P<0.01) and on body weight, egg height , egg width, average egg shell colour (P<0.05). Strain did not affect (P>0.05) average feed intake, body weight change, egg output, feed conversion ratio, mortality rate, egg shell breaking force, albumen height, yolk height, yolk weight, extra-large and jumbo graded eggs percentage. Brown Hy-Line layers had high average egg weight, median egg weight, egg height, egg width, and average egg shell colour and albumen weight than White Hy-Line layers. Small sized eggs percentage and body weight were high on White Hy-Line layers compared to Brown Hy-Line layers. Medium and large sized eggs were high on Brown Hy-Line layers than White Hy-Lines. Feed withdrawal by strain interaction effect was observed on body weight, average egg weight and median egg weight, albumen weight and egg height, percentage of small, medium and large graded eggs (P<0.05). Brown Hy-Line hens under eight hours feed withdrawal had high egg weight, median egg weight, egg height, albumen weight and under eight hours feed withdrawn White Hy-Line hens had lower albumen height compared to other interactions. In all interactions White Hy-Line had high percentage of small graded eggs whereas Brown Hy-line had high percentage of large and medium graded eggs. / NRF

Although pregnant viviparous squamates are sometimes claimed to be able to resorb inviable eggs and embryos from the uterus, definitive evidence for such resorption is not available. After placing pregnant female Pseudemoia pagenstecheri into conditions under which embryonic development is terminated, we periodically harvested the gravid oviducts and examined them histologically. Females contained abnormal and degenerating eggs and embryos that had died in various stages of development. Dead embryos had undergone extensive cytolysis, dissolution, and aseptic necrosis and vitelline masses showed signs of deterioration and passage down the oviduct. The uterine mucosa lay in direct contact with the vitelline material, with no intact shell membrane intervening between them. Yolk was sometimes displaced into the exocoelom and allantoic cavity due to rupture of the extraembryonic membranes. Histological examination revealed no evidence of the uptake of yolk by the uterine epithelium or its accumulation in the subepithelial connective tissue. In many specimens, the uterine epithelium showed minuscule, apical granules. The position, appearance, and staining properties of the granules suggests them to be secretory, a manifestation of placentotrophy. Our observations indicate that P. pagenstecheri females retain dead eggs and embryos for several weeks or longer, yet do not resorb them during that period. This lizard is the second placentotrophic skink species in which resorption has been suspected, but in which abortive eggs appear to be retained or extruded instead of being resorbed by the oviducts. Researchers should not assume that squamates can digest and resorb oviductal eggs without definitive morphological evidence.

The decade from 1953 to 1963 was one of drastic change for the egg industry in Utah. A study conducted at Utah State University shows that in 1952, slightly more than 40 percent of local egg production was s old in distant markets while in 1964, import data gathered from egg handlers in the State indicate that 20 to 25 percent of the eggs consumed in Utah were imported.

This study tested different concentrations of egg yolk in canine freezing extender void of glycerol, a commonly used cryoprotectant, by examining the motility and morphology throughout the freezing process: initial (baseline after extender added), post-cool (after three hours at 5"C) and post-thaw (after freezing.)  Initial values of pH, osmolarity, motility and morphology were obtained for comparison of the samples.  Spermatozoa from six normal dogs as determined by progressive linear motility > 70% and normal morphology > 60% was used. Semen was collected and pooled for five freezing trials.  The concentrations of egg yolk used in the extender were: 0%, 10%, 20%, 30% and 40%. Assessment of each sample was blinded to the treatments until all results were obtained and statistics had been analyzed. Based on this study a 20% egg yolk concentration is slightly superior to a 30% egg yolk concentration when assessing post-thaw motility, morphology and longevity and significantly superior to a 0%, 10% or 40% egg yolk concentration. The study also showed motility and normal post-cool and post-thaw sperm morphology did not always correlate.  Utilization of 0% and 10% concentrations of egg yolk has negative effects on semen quality as measured by the motility and/or morphology.  Results confirm freezing does not affect secondary sperm abnormalities, abnormalities of the tail and distal section of the middle piece, during cooling or freezing.  Primary abnormalities, abnormalities of the head and midpiece, increased in the 0% extender during cooling and all extenders during freezing. The pH of the extenders before the addition of sperm was significantly different. Once sperm was added to the extenders, there was no longer a significant difference in pH.  There was a positive correlation for both motility and normal morphology percentages post-cool and post-thaw for the extenders with similar osmolarity to the semen. / Master of Science

<p> This thesis examines the operations of the Canadian Egg Marketing Agency and its provincial boards and their effects on producers, consumers and the agricultural industry. The variables that were reviewed to achieve this objective were: producer and retail price levels, the stability of producer and retail prices, the price differences between the provinces, the amount of imports and exports, the role of supply and demand in determining price and the producers' share of the consumer dollar. Two techniques were used. One method was the before and after technique which compared two periods, 1961-71 and 1975-82, to identify what changes had occurred since the introduction of CEMA in 1973. The second method was a comparison to the United States which control led for market structure changes. </p> <p> The results of this study are as follows. Producers have benefited from CEMA's operations through greater price stability, a larger share of the consumer dollar and from a higher price level than in the United States. CEMA has affected consumers by stabilizing retail prices and equalizing prices across the country. However, CEMA's actions have redistributed income from consumers to producers. CEMA has had a positive effect on the agricultural industry by increasing exports while import levels have remained the same. </p> / Thesis / Candidate in Philosophy

Mycoplasma gallisepticum (MG) is a major and economically significant pathogen of avian species. Different strains of MG have been used as vaccines in multiple-age commercial layer farms in an effort to protect the birds against more virulent field strains. The lower level of protection afforded by the low virulent MG strain vaccines provides an opportunity to the use of an overlay (revaccination) with an F-strain M. gallisepticum (FMG) later in their production cycles. In the present study, three trials were conducted to investigate the effects of prelay vaccinations of ts-11 strain MG, MG-Bacterin, or their combination, in conjunction with a FMG overlay after peak production in commercial layers. The following treatments were utilized at 10 wk of age (woa): 1) Control (no vaccinations); 2) ts-11 MG vaccine; 3) MG-Bacterin vaccine; and 4) ts-11 MG and MG-Bacterin combination. At 45 woa, all the birds in trial 1 and half of the birds in each treatment group in trials 2 and 3 were overlaid with an FMG vaccine. Various parameters including performance, internal egg and eggshell quality, blood, and visceral characteristics of the birds were evaluated. In this study, the ts-11 MG vaccination at 10 woa was shown to increase shell weight and the yolk lipid content of the eggs laid by the birds without affecting their performance. On the other hand, a prelay vaccination with MG-Bacterin did not prevent a drop in egg production in response to an overlay with FMG at 45 woa. A decrease in proportional infundibulum length in the control birds and MG-Bacterin vaccinated birds after being overlaid with FMG might be the underlying factor responsible for the observed decrease in egg production. Nevertheless, the prelay use of MG-Bacterin together with ts-11 MG didn’t appear to provide any additional benefit over the ts-11 MG vaccine alone on any of the parameters investigated. In conclusion, these results establish the potentially effective prelay use of the ts-11 MG vaccine in combination with an FMG overlay for the provision of continual protection against field strain MG infections, without eliciting any subsequent suppressive effects on the performance of commercial layers.

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