title: The effect of dietary carbohydrate composition on apparent total tract digestibility, feed mean retention time, nitrogen and water balance in horses.
abstract: A total of four diets with different carbohydrate composition were investigated in a 4×4 Latin square design experiment with four Norwegian Coldblooded trotter horses. The objective of the present study was to increase the fermentable fibre content and reduce the starch intake of the total ration obtained by partly substituting mature hay and barley with sugar beet pulp (SBP), a soluble fibre source. The diets investigated were hay only (HAY), hay (85% of dry matter intake (DMI)) and molassed SBP (15% of DMI) (SBP), hay (68% of DMI) and barley (32% of DMI) (BAR), and hay (68% of DMI), barley (26% of DMI) and SBP (6% of DMI) (BAR+SBP). The feeding level was 18.5, 17.3, 15.7 and 15.7 g DM/kg BW per day for the HAY, SBP, BAR and BAR+SBP diets, respectively. Each diet was fed for 18 days followed by 10 days of data collection, where apparent total tract digestibility (ATTD), total mean retention time (TMRT) of ytterbium-labelled hay, water balance, digestible energy (DE) intake and nitrogen balance were measured. An enzymatic chemical dietary fibre (DF) method was used to get detailed information on the composition and ATTD of the fibre fraction. Inclusion of SBP in the diet increased the ATTD of the constituent sugars galactose and arabinose (P<0.01). Feeding the HAY and SBP diets resulted in a lower TMRT owing to a higher DF intake than the BAR and BAR+SBP diets (P<0.01). There was no difference in water intake between HAY and SBP, but faecal dry matter was lower for HAY than the other diets (P=0.017), indicating that water was more tightly bound to fibre in the HAY diet. The diets were iso-energetic and provided enough DE and protein for light to moderate exercise for a 550 kg horse. In conclusion, this study showed that the DF intake had a larger effect on TMRT than partly substituting hay or barley with SBP, and that highly fermentable pectin-rich soluble DF from SBP maintains high nutrient utilization in horses.
authors.affiliation: 1Department of Veterinary Clinical and Animal Sciences, Faculty of Health and Medical Sciences,University of Copenhagen,DK-1870 Frederiksberg C,Denmark.
authors.forename: R B
authors.initials: RB
authors.lastname: Jensen
authors.affiliation: 2Department of Animal and Aquacultural Sciences,Norwegian University of Life Sciences,NO-1430 Ås,Norway.
authors.forename: D
authors.initials: D
authors.lastname: Austbø
authors.affiliation: 3Department of Animal Science, Faculty of Science and Technology,University of Aarhus,DK-8830 Tjele,Denmark.
authors.forename: K E
authors.initials: KE
authors.lastname: Bach Knudsen
authors.affiliation: 1Department of Veterinary Clinical and Animal Sciences, Faculty of Health and Medical Sciences,University of Copenhagen,DK-1870 Frederiksberg C,Denmark.
authors.forename: A-H
authors.initials: AH
authors.lastname: Tauson
mesh_terms: D000821:Animal Feed / Q000032:analysis; D000824:Animal Nutritional Physiological Phenomena; D000818:Animals; D027461:Beta vulgaris / Q000737:chemistry*; D004032:Diet / Q000662:veterinary; D004040:Dietary Carbohydrates / Q000008:administration & dosage / Q000378:metabolism*; D004043:Dietary Fiber / Q000008:administration & dosage / Q000378:metabolism*; D004063:Digestion; D004305:Dose-Response Relationship, Drug; D002149:Energy Intake; D006736:Horses / Q000502:physiology*
chemical_list: D004040:Dietary Carbohydrates; D004043:Dietary Fiber