京都大学 / 0048 / 新制・課程博士 / 博士(農学) / 甲第22074号 / 農博第2366号 / 新制||農||1072(附属図書館) / 学位論文||R1||N5228(農学部図書室) / 京都大学大学院農学研究科地域環境科学専攻 / (主査)教授 近藤 直, 准教授 小川 雄一, 教授 飯田 訓久 / 学位規則第4条第1項該当 / Doctor of Agricultural Science / Kyoto University / DFAM

<p dir="ltr">The White Pekin duck (<i>Anas platyrhynchos domesticus</i>) is the most widely consumed duck protein in the world. Total duck meat production had a global annual increase of 2.1% per year from 2010 to 2019. The increase in duck meat production can be credited to improved management strategies, nutritional programs, and genetic improvement made to the Pekin ducks by structured breeding programs. Regardless of the advancements already achieved by Pekin duck breeding programs, improvements can still be made. One such improvement that can be made in Pekin duck populations is reducing the frequency of the emerging welfare concern known as flip-over (FO). We hypothesize that egg quality traits, wingspan, back length, and hip width are genetically influenced and their inclusion into Pekin duck breeding programs can be used to improve the Pekin duck. Egg quality traits were collected at weeks of age 30, 32, 35 and 40 on two generations of Pekin duck hens. All heritability estimates and Genetic correlations were calculated using BLUPF90 software, the Restricted Maximum Likelihood (REML) method, and 9,418 individuals in the pedigree. All egg quality traits evaluated are moderate to highly heritable ranging from 0.23 for egg shape to 0.70 for shell ratio. Two hatches of 1,200 Pekin duck hens were assessed at day of age 23 and 30 for wingspan, hip width, and back length using image analysis. Wingspan, hip width, and back length were found to be heritable ranging from 0.04 ± 0.013 to 0.27 ± 0.025 for hip width and back length respectfully. This thesis will discuss approaches to evaluating genetic parameters of egg quality traits in hatching eggs and the possibility of reducing FO through the selection of increased wingspan length.</p>

The F-strain of Mycoplasma gallisepticum (FMG) is commonly used in vaccination programs to displace infections by more virulent natural or wild type Mycoplasma gallisepticum strains. However, a better understanding of the mechanisms responsible for altered egg production (EP) and egg quality in commercial layers infected with FMG is important, as these alterations can cause economic loss to the United States layer industry. This study was designed to examine potential mechanism(s) responsible for alterations in EP and egg quality by FMG-inoculation. The effects of FMG on production parameters and physiological characteristics of commercial laying hens were evaluated. In isolation units, 12 wk FMG inoculation delayed onset of lay approximately one wk, decreased overall EP, and decreased EP 34 wk post-inoculation. A 12 wk FMG inoculation also resulted in a higher incidence of fatty liver hemorrhagic syndrome, ovarian follicular regression, and decreased isthmal and vaginal proportions of the reproductive tract. Ovarian regression may be related to retarded production (liver), transport (blood), and/or uptake (ovary) of yolk particles. Changes in blood characteristics (i.e. lipid composition) with FMG colonization of the liver may become manifest through changes in egg constituents. As evidenced through changes in the relative weights of various reproductive organs, colonization of these organs by FMG, in addition to the liver, may also be a cause of the effects observed on EP. Increases in hematocrit, serum triglycerides, and plasma protein between 8 and 10 wk post FMG-inoculation, suggest that the initial weeks of EP are stressful. Post-peak decreases in these same variables suggest a more chronic inhibition on lipid and protein synthesis in the liver. Decreased blood lipid concentration may be directly responsible for the reductions in yolk lipid, cholesterol, and fatty acid deposition in 12 wk FMG-inoculated hens. Dual adverse effects in the caged layer facility on feed conversion and egg mass were realized in 22 wk FMG-inoculated birds. In contrast, a 12 wk FMG inoculation delayed onset of lay without a loss in total EP or egg mass. Therefore, inoculation with FMG at 12 wk is more practical and cost effective. Higher degrees of physiological stress experienced by hens in a caged layer facility may exacerbate the effects of FMG inoculation seen in the isolation units. These data demonstrate that alterations in performance and egg characteristics of commercial layers inoculated with FMG at either 12 or 22 wk of age and housed in either isolation units or caged layer facilities are related to mutual functional disturbances in the blood, liver, ovary, and oviduct without concomitant intestinal changes.

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