Summary Discs of stripped mucosa from the proximal ventral colon were prepared immediately after slaughter of 8 Shetland cross‐breed ponies. The mucosae were fixed in incubation chambers and used in incubation experiments to study the transmucosal fluxes of the amino acids lysine, histidine and arginine (150 min) and of ammonia (90 min). When the amino acid concentrations in the mucosal solution were in the physiological range (2.8–3.0 mmol/l) no transport to the serosal side of the tissue was found. When the concentrations were raised 10‐fold, less than 2% of the mucosal amino acid pool was recovered in the serosal solution. Ammonia was transported across the mucosa at significant rates although only 63% of the ammonia that disappeared from the mucosal solution was found in the serosal solution. The findings show that the equine proximal colon is virtually impermeable to luminal free amino acids whereas ammonia is transported at rates equal to, or higher than those observed with rumen mucosa from sheep.

Zusammenfassung An zwei laktierende Ponystuten wurde eine lysindefizitäre Basisration gefüttert und in vier Perioden mit gestaffelten Zulagen von synthetischem Lysin ergänzt. Der kalkulierte Lysinbedarf war in den Perioden I‐IV zu ≅ 78, 92, 112 und 133% gedeckt. Zu Beginn jeder Periode wurde eine einmalige Dosis von 15N‐Lysindihydrochlorid oral mit dem Kraftfutter verabreicht. Harn, Milch und Kot wurden innerhalb 36 Stunden gesammelt. Die Messung der 15N‐Anreicherung erfolgte emissions‐spektrometrisch. Als Kriterium für den Bedarf an Lysin galt dessen Katabolismus, charakterisiert durch die renale 15N'‐Exkretion. Die Berechnung des Lysinbedarfes aus dem Anstieg sowohl der kumulativen 15N'‐Exkretion als auch der mittleren 15N'‐Häufigkeit im 36‐Stunden‐Harn nach dem ‘broken line’ Verfahren führte zu gleichen Ergebnissen. Unter den im Versuch gegebenen Bedingungen erreichten die Stuten eine bedarfsdeckende Aufnahme bei 2,8 (Tier 1) bzw. 2,9 g Lysin/kg Milch (Tier 2). Die gewählte Methode erwies sich für die Ermittlung des Aminosäurenbedarfes laktierender Stuten als geeignet.

Chopped wheat straw was homogeneously mixed with horse urine

Chopped wheat straw was homogeneously mixed with urine of horses (5.75 gN per 1, 16.88 atom-% 15N-excess) and airtightly stored in plastic containers for 6 months. Three rumen fistulated sheep and goats each were fed with untreated or urine treated straw. Concentrate was added to straw. Untreated and urine treated straw were given in nylon bags and incubated in the rumen of sheep and goats for 1, 3, 6, 12, 24, 48 and 72 hours. A three compartment exponential function was used to fit the measurements of 15N-excess and 15N-amount of bag content. The curves and the calculated partial Y-values of the three compartments show the inflow and outflow of 15N into or from the bags and allow conclusions about the binding of urine N. Most N of urine was not compactly bound by straw during storage. Primarily microbial N was attached to the straw in the rumen. About 6% of urine N were bound more compact to the straw. Similar curves were calculated for 15N-excess and 15N-amount of nylon bags. The curves allow conclusions about tracer flows without quantitative knowledge. There were no significant differences between animal species.