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Title: The effect of management regimes on large intestinal function in the horse
Author: Williams, Sarah
ISNI:       0000 0004 2742 708X
Awarding Body: University of Nottingham
Current Institution: University of Nottingham
Date of Award: 2012
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Management factors, particularly those linked to stabling horses, are identified as risk factors for equine colic in several epidemiological studies. Impaction colic in particular, is linked with restricted water intake, changes in feeding practices and reduced activity and these are likely to mediate an effect through altering ingesta hydration and intestinal motility. This study aimed to provide new information on the effect of management regimes on large intestinal function in the horse. In particular, how management regimes affect intestinal motility and gastrointestinal water balance. This information may contribute to explaining the mechanisms of large colon impactions and the increased risk of colic in stabled horses. Single large concentrate meals/intermittent feeding have also been shown to induce systemic dehydration in the horse and therefore stimulate water absorption in the equine large intestine through activation of the renin- angiotensin-aldosterone system (RAAS). Therefore molecular analysis was used in this study to characterise aquaporin water channels (AQPl-4) in the equine intestine and renal receptors, which are targets of the RAAS in equine kidney. The aim was to provide preliminary data for further research. Live animal studies were used to investigate the effectiveness of transcutaneous ultrasonography in visualising abdominal structures in the horse. This technique was used to investigate large intestinal motility between a stabled and a pastured regime, and to investigate the effect of a management change from pastured to stabled. Data showed that large intestinal motility was significantly reduced in stabled horses compared to when horses were pastured, and this was most marked in the aboral left ventral colon (pelvic flexure region). Large intestinal motility was also significantly reduced in the caecum and large ventral colon on Day 1 post-management change, and in the left aboral ventral colon (pelvic flexure region) only on Day 4. Motility was significantly increased in the caecum and large ventral colon on Day 5 post- management change. Drinking water intake was significantly increased across all days in the two weeks following a change to stabling, and faecal output and faecal water content were significantly reduced. Western blot and immunohistochemical analysis were challenging in equine cadaver tissue. Both molecular techniques identified Na-K-ATPase in equine kidney and intestine. However, antibodies for other renal receptors and AQP2 failed to cross-react with equine tissue in this study. AQPl was identified in equine kidney and erythrocytes but not in intestinal tissue. Western blot analysis revealed AQP3 and AQP4 in equine intestinal and renal tissue. However, immunohistochemical results showed non-specific staining that was identical to that of negative serum controls. Therefore results could not be interpreted with confidence. In conclusion, work in this thesis has demonstrated changes in large intestinal motility, water intake and faecal water content, all of which contribute to our understanding of large colon impaction in stabled horses. It has also highlighted some of the challenges of using molecular techniques in equine intestinal tissue and also linking physiological changes at the molecular level with effects in the live animal.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available