Animal. 2016 Jul;10(7):1155-63. doi: 10.1017/S1751731115003006. Epub 2016 Jan 12.
- 11Department
of Veterinary Clinical and Animal Sciences, Faculty of Health and
Medical Sciences,University of Copenhagen,Grønnegaardsvej 3,DK-1870
Frederiksberg C,Denmark.
- 22Department of Animal and Aquacultural Sciences,Norwegian University of Life Sciences,Box 5003,N-1432 Ås,Norway.
- 33School
of Animal Biology, Faculty of Natural and Agricultural
Sciences,University of Western Australia,35 Stirling
Highway,Crawley,Perth, WA 6009,Australia.
- 44Department of Animal Science,Aarhus University,Blichers Allé 20,DK 8830 Tjele,Denmark.
Abstract
The
hypothesis for this study was that a higher dietary proportion of
soluble fibre would result in stable and constant plasma metabolite and
regulatory hormone concentrations. The study was a 4×4 Latin Square
design with a sequence of 17 days adaptation to the ration followed by 8
sampling days. The feed rations consisted of only timothy hay (H), hay
plus molassed sugar beet pulp combined with either whole oats (OB) or barley (BB) and hay plus a loose chaff-based concentrate (M). Four horses
were fitted with permanent caecal cannulas and liquid caecal content
was withdrawn manually and blood was drawn from the jugular vein at 0, 3
and 9 h postprandial. The horses
were exercised daily at medium level for about 1 h. Samples were
analysed for short-chain fatty acids (SCFA) and metabolic traits. Caecal
SCFA and propionic acid concentrations increased with increased dietary
starch and soluble fibre. The diet highest in soluble fibre (M)
resulted in the highest plasma glucose and insulin concentrations in the
morning, which then remained stable and constant throughout the day. A
strong interaction (P<0.01) between time and diet was measured for
plasma urea, glucose, insulin and leptin. The greatest variations in
plasma glycaemic and insulinaemic responses were associated with the
cereal grain diets (OB and BB). There were indications of a negative
energy balance, which was reflected in a significantly higher plasma
β-hydroxybutyrate concentration and a numerically higher non-esterified
fatty acid concentration. In conclusion, this study found that inclusion
of soluble fibre resulted in increased total caecal SCFA and propionic
acid concentrations. This consequently resulted in stable and constant
plasma glycaemic and insulinaemic responses. Diets with a high content
of soluble fibre provided enough energy for horses at medium work level.
KEYWORDS:
caecal SCFA; dietary fibre; horse; metabolites; regulatory hormones