title: Nitrogen digestion and urea recycling in Hokkaido native horses fed hay-based diets.
abstract: Nitrogen (N) digestion and urea-N metabolism in Hokkaido native horses fed roughage-based diets containing different types and levels of protein sources were studied. Horses (173 ± 4.8 kg) fitted with an ileum cannula were fed four diets consisting of 100% timothy hay (TH), 88% TH and 12% soybean meal (SBM), 79% TH and 21% SBM, and 51% TH and 49% alfalfa hay at 2.2% of body weight. Dietary protein content varied from 5% to 15% of dry matter. Apparent N digestibilities in the pre-cecum and total tract for the TH diet were lower than those for other diets. However, the proportion of post-ileum N digestion to N intake was not affected by the diets. Urea-N production was linearly related to N intake, but gut urea-N entry was not affected by the diets. The proportion of gut urea-N entry to urea-N production tended to be higher for the TH diet (57%) than the two SBM diets (39%). Anabolic use of urea-N entering the gut was not affected by the diets (20-36% of gut urea-N entry). These results indicate that urea-N recycling provides additional N sources for microbial fermentation in the hindgut of Hokkaido native horses fed low-quality roughages.
authors.affiliation: Graduate School of Biosphere Science, Hiroshima University, Higashihiroshima, Japan.
authors.forename: Taketo
authors.initials: T
authors.lastname: Obitsu
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Hata
authors.forename: Kohzo
authors.initials: K
authors.lastname: Taniguchi
mesh_terms: D000821:Animal Feed / Q000032:analysis; D000818:Animals; D002417:Cattle / Q000378:metabolism*; D004044:Dietary Proteins / Q000032:analysis / Q000378:metabolism; D004063:Digestion / Q000502:physiology*; D005285:Fermentation; D041981:Gastrointestinal Tract / Q000378:metabolism / Q000382:microbiology; D007564:Japan; D000455:Medicago sativa; D009584:Nitrogen / Q000378:metabolism*; D031784:Phleum; D013025:Glycine max; D014508:Urea / Q000378:metabolism*
chemical_list: D004044:Dietary Proteins; D014508:Urea; D009584:Nitrogen
keywords: digestion; horse; nitrogen utilization; urea recycling