(1). In this thesis the relationship between eggshell quality and bone biology was examined over the laying life of two strains of hen; a highly selected commercial line and the relatively unselected J.Line. (2). The efficiency of using osteocalcin as a marker of osteoid formation, in collaboration with established markers of bone mineralisation and bone resorption, during eggshell calcification was ratified. (3). It was established that magnesium is actively removed from bone hydroxyapatite during resorption and transported to the shell gland pouch for incorporation into the palisade layer of the eggshell. (4). A relationship was demonstrated between hatched eggshell quality and the bone biology of newly hatched chicks. (5). The association between high egg output and poor bone structure was evident in the commercial laying strain hen. No such deficit in skeletal quality occurred in the relatively unselected J.Line. (6). The commercial line demonstrated a significantly higher rate of bone remodelling at late lay concomitant with osteoporosis. (7). The unselected J.Line demonstrated significantly higher rates of bone remodelling throughout lay. It was hypothesised that this was due to a greater propensity for bone upkeep during the inter-egg interval. (8). The provision of a prelay diet influenced neither bone volume nor mineral composition at the beginning of lay. (9). The feeding of a prelay diet led to a longer period of sustained high production and an earlier increase in egg weight. This was accompanied by a delay in the increase in osteoid formation and decreased levels of blood ionised calcium. This led to high "on farm" seconds at late lay due to abnormally high fracture toughness and the Incidence of type B's within the mammillary layer. (10). The reason for the observed decrease in hatchability associated with poorly pigmented eggshells in a commercial guinea fowl flock was related to premature expulsion of the egg. These thinner shelled eggs may have resulted from the process of artificial insemination.
| Identifer | oai:union.ndltd.org:bl.uk/oai:ethos.bl.uk:301513 |
| Date | January 1999 |
| Creators | Darnell-Middleton, Sally Louise |
| Publisher | University of Glasgow |
| Source Sets | Ethos UK |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
| Source | http://theses.gla.ac.uk/30935/ |
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