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The effect of diet on certain aspects of the eggshell of the domestic fowl (Gallus domesticus)
Başlık:
The effect of diet on certain aspects of the eggshell of the domestic fowl (Gallus domesticus)
Yazar:
Reid, Jacqueline, author.
ISBN:
9780438060890
Yazar Ek Girişi:
Fiziksel Tanımlama:
1 electronic resource (238 pages)
Genel Not:
Source: Dissertation Abstracts International, Volume: 76-08C.
Advisors: S. Solomon.
Özet:
Initial investigations included a study of egg production and shell weight/thickness in birds fed different dietary regimes some of which included methyl mercury. Results indicated that methyl mercury fed at a rate of 9ppm for periods of up to twelve weeks did not cause shell thinning although it did seem to make the birds' laying pattern more erratic. In those birds fed diets supplemented with mercury its absorption was shown to have taken place by the neutron activation analysis of mercury in their oviducal tissues. The tubular shell gland and shell gland pouch regions of the oviduct were analysed and although the ingested mercury appeared to accumulate in both these tissues the highest levels were found in the tubular shell gland. As this is the part of the oviduct which is responsible for initial mineralisation of the mammillary cores it was considered a possibility that mercury could affect shell structure by influencing the mechanism of crystal deposition. On the basis of this and a report in the literature by Kennedy (1979) that methyl mercury could affect the mammillary layer of the eggshell, a study of this region was undertaken. It was decided to investigate the mammillary layer using the scanning electron microscope, but preparation of shells for this technique involved removal of the closely adherent outer shell membrane which is firmly bonded to the crystalline shell at the basal cap of each mammilla. Previously described methods of membrane removal had made use of caustic chemicals which often resulted in damage to the underlying crystals. Since these first crystals of calcification were to be studied it was necessary to develop a method of membrane removal which would leave them intact. The treatment of shells with an activated gas plasma in the Nanotech Plasmaprep apparatus satisfied these criteria and subsequently became the method of membrane removal used in the studies of the mammillary layers of both control and experimental shells, A range of normality was first established for the morphology of the mammillary layer by examining the shells of birds fed a commercial layers diet. There was great variation in the density of mammillary bodies both in different areas of the same shell and between shells. The morphology of the basal cap region of these shells also showed considerable variation and in addition to fusion of otherwise normal basal caps, three crystalline changes were identified. Two of these (cauliform and denuded) were later shown to be derived from shell membrane and related to each other, but the third (rudimentary type A) appeared to be completely different in origin. At a slightly deeper level in the shell, viz. the mammillary cone layer, spherical structures referred to as rudimentary type B abnormalities were found. The examination of shells from birds fed various experimental diets, some of which contained methyl mercury, showed an increase in the incidence of mammillary abnormalities compared with the shells of birds fed layers diet. The addition of mercury to the diet appeared to exacerbate this effect. An additional basal cap abnormality was found (swallows nest) and the three changes occurring at the level of the basal cap were shown to be derived from shell membrane with a greater than normal inorganic component. The finding of aragonite in the cone layer of shells from the experimental groups represented a change in the calcium carbonate crystal modification. Evidence was presented which implicated an increase of dietary sulphur in the formation of basal cap abnormalities and aragonite. Although the mammillary changes found were not considered to be consistant with the formation of good shell material, any connection between them and poor quality shells was speculative. However the demonstration of similar abnormalities in supermarket eggs selected for their fragile or poor quality shells suggested that there might be a positive correlation. Finally a study was undertaken to investigate cuticle production when birds were fed layers diet as well as experimental diets. Whereas mercury was only found to exacerbate the effects of the basic experimental diet on the mammillary layer of the shell, ingested methyl mercury appeared to interfere directly with production of cuticle resulting in a high proportion of cuticle-less shells.
Notlar:
School code: 0547
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Yer Numarası | Demirbaş Numarası | Shelf Location | Lokasyon / Statüsü / İade Tarihi |
---|---|---|---|
XX(684857.1) | 684857-1001 | Proquest E-Tez Koleksiyonu | Arıyor... |
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