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dc.contributor.authorMcLean, Barbara Margaret Lammieen
dc.date.accessioned2019-02-15T14:36:27Z
dc.date.available2019-02-15T14:36:27Z
dc.date.issued2001en
dc.identifier.urihttp://hdl.handle.net/1842/35269
dc.description.abstracten
dc.description.abstractCereal and legume starch frequently constitute the majority of the concentrate portion of diets for equines yet large intakes of starch can be associated with changes to the hindgut environment. Cereal and legume grains are often subjected to some form of physical processing with a view to increasing their digestibility and this has been the subject of a number of studies. However, there are few reports of the effects of such processing on either the hindgut environment or the site of starch degradation in the equine. Therefore, the objectives of this thesis were twofold, firstly to investigate the effects of physical processing of grains on intra-caecal fermentation parameters and secondly to develop in sacco methodologies to enable degradation parameters of processed cereals to be determined in different segments of the equine digestive tract. In the first set of experiments three caecally fistulated ponies were offered 4 kg DM per day of either 100% hay cubes (HC) or one of three diets consisting of 50:50 barley:HC mix. The barley in the mixed diets was either rolled (RB), micronised (MB) or extruded (EB). Inclusion of RB in the diet significantly (P<0.05) reduced intra-caecal pH and acetate molar proportions whilst lactate concentration and propionate molar proportions were increased (P<0.05) compared with the HC diet measured 5 hours post feeding. Physical processing of grains did not alter their total tract in vivo apparent digestibility nor their digestible energy (average 14.8 MJ/kg DM) or digestible crude protein (average 86 g/kg DM) contents. Mean retention times (MRT) of digesta were determined for the four diets and were similar at 46.1, 42.3, 46.9 and 43.0 h for HC, RB, MB and EB respectively. In the second set of experiments micronised or extruded barley, maize and peas were incubated in situ in the caecum of ponies to determine their degradation parameters. Compared to unprocessed feeds, micronisation significantly increased (P<0.05) the effective degradability (ED) of starch (STC) but reduced the ED of crude protein (CP) in barley and maize. Likewise extrusion of maize increased and decreases the ED of maize starch and CP respectively. However, extrusion of barley had no effect on the ED of the STC fraction but decreased that of the CP. Neither extrusion or micronisation had an effect on the ED of starch or protein in peas. It was noted that incubation sequence had no significant effect on any of the measured degradation parameters of these starch-based feeds. In a third set of experiments a mobile bag technique was developed to determine the degradation parameters of the above feedstuffs both precaecally and over the whole digestive tract of ponies. Bags were administered directly into the stomach of two caecally fistulated ponies via a naso-gastric tube. The bags were then retrieved either at the ileo-caecal junction via a magnet placed in the caecal fistula or in the faeces. Site of recovery of bags had a significant effect (P<0.05) on DM, STC and CP losses and these effects were particularly marked for maize. Both micronisation and extrusion increased pre-caecal DM and STC losses from barley, maize and peas compared to unprocessed grains. Micronisation and extrusion of maize resulted in increased pre-caecal and decreased total tract losses of CP compared to unprocessed maize. Precaecal degradation parameters for barley were determined demonstrating an increase in the ED of DM for barleys which had been micronised or extruded. The lower ED of unprocessed barley in the pre-caecal segment of the equine digestive tract may account for the differences in intra-caecal fermentation parameters recorded in the first set of experiments. Further development of in sacco techniques should allow the digestion of feedstuff in the equine digestive tract to be partitioned enabling the identification of processing methods which minimise alterations in intra-caecal fermentation parameters.en
dc.publisherThe University of Edinburghen
dc.relation.ispartofAnnexe Thesis Digitisation Project 2019 Block 22en
dc.relation.isreferencedbyAlready catalogueden
dc.titleMethodologies to determine digestion of starch in poniesen
dc.typeThesis or Dissertationen
dc.type.qualificationlevelDoctoralen
dc.type.qualificationnamePhD Doctor of Philosophyen


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