The identification, rationalization and correlation of physiological and behavioural responses to stress

Edmond, Avril (2002) The identification, rationalization and correlation of physiological and behavioural responses to stress. PhD thesis, University of Glasgow.

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Abstract

This thesis describes a multidisciplinary approach to the measurement of bird welfare. In chapter 2 commercial and traditional lines of layer birds were compared to determine time of onset of lay and the occurrence of superficial shell abnormalities. The commercial lines laid earlier, a feature consistent with the demand for high egg production in these strains and these eggs also displayed an increased incidence of surface defects at that time. Following the move to cages, shell quality was similar across all lines. Experiment 2 permitted an evaluation of specific stress responses, in terms of eggshell quality, plasma corticosterone levels and prior simple tests of avoidance across all breed types. The results were inconsistent suggesting that each measure was assessing a different aspect of the bird's response. Chapter 3 describes an in-house trial constructed to detect the immediacy or otherwise of the bird's response to stress. The more in-depth investigation applied in this work facilitated comment to be made on the intra-shell location of defects associated with the stress response. In terms of shell quality, the response was not immediate and was more pronounced in birds moved into pens with a variety of enrichments. The complex variables associated with this experiment were too diverse to dissect out and dissociate from each other. In the second experiment more defined acute and chronic stressors were applied and it was clear that the time delay, in terms of bird response, was real but was only elicited in those birds which had experienced acute stress. Shell quality defects are not the prerogative of the layer bird and in chapter 4 the effect of rearing enrichment on subsequent broiler breeder performance illustrated improvements in both the physical / material and structural quality of the eggshell from mid lay onwards. Previous chapters have highlighted the fact that the eggshell can be used as a non-invasive indicator of welfare. In Chapter 5 this methodology was applied to a multi-tier system to determine tier effect with respect to product quality under normal commercial conditions. Eggs from the top and bottom tiers demonstrated a variety of shell and internal quality variables which correlated with specific environmental parameters viz lighting, temperature and ammonia concentration. Chapter 6 describes the consolidation of the measurements of eggshell quality currently available. Resonance frequency testing is a simple, cost-effective, non-destructive measure of egg quality with the potential to distinguish not only cracked eggs but those predisposed to crack at some point during routine handling.

Item Type: Thesis (PhD)
Qualification Level: Doctoral
Additional Information: Adviser: Maureen Bain
Keywords: Animal sciences
Date of Award: 2002
Depositing User: Enlighten Team
Unique ID: glathesis:2002-73406
Copyright: Copyright of this thesis is held by the author.
Date Deposited: 14 Jun 2019 08:56
Last Modified: 14 Jun 2019 08:56
URI: http://theses.gla.ac.uk/id/eprint/73406

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