Rumen ammonia concentrations, and non-ammonia nitrogen passage to and apparent absorption from the small intestine of sheep ingesting subtropical, temperate, and tannin-containing forages

Abstract

Non-ammonia nitrogen (NAN) passage to the small intestine and disappearance of NAN in that organ have been studied in multi-cannulated sheep on pasture or fed indoors. Forages under investigation included a number of subtropical grasses, foggages and hay, temperate grasses, lucerne (Medicago sativa), triticale (Triticale X Secale), oven-dried ryegrass (Lolium multiflorum), and the tannin-containing forages sainfoin (Onobrychis viciifolia) and sheeps' burnet (Sanguisorba minor). Digesta flow was measured with reference to Yb-acetate and Cr-EDTA as particulate and fluid markers, respectively. Rumen ammonia concentrations were exponentially associated with the nitrogen (N) content of the forage, with concentrations increasing progressively above 2.5% N in the forage dry matter. Ruminal fermentation of tannin-containing forages resulted in much lower ammonia concentrations than ruminal fermentation of forages without tannins. NAN passage to the small intestine as a proportion of N intake was significantly (P ≤ 0.05) different between forage classes: 0.97 ± 0.09 for subtropical forages, 0.75 ± 0.09 for temperate grasses plus lucerne and triticale, and 1.12 ± 0.08 for tannin-containing forages and dried grass. NAN passage as a proportion of N intake declined with increasing N intake in all non-tannin forages, the decline being especially severe in forages with high total (above 3%) and/ or high soluble N. NAN disappearance in the small intestine as a proportion of NAN entering that organ differed significantly (P ≤ 0.01) between tannin-containing forages and subtropical foggages and hay on the one hand (0.64 ± 0.06), and all other forages on the other hand (0.76 ± 0.02). NAN disappearance as a proportion of N intake increased in the order: temperate grasses plus lucerne and triticale, subtropical foggages and hay, subtropical grasses, tannin-containing forages, and dried grass.

Die vloei van nie-ammoniak stikstof (NAN) na, en die verdwyning daarvan in die dunderm is bestudeer in meervoudig-gefistuleerde skape op weiding of binnenshuis gevoer. Ruvoere wat bestudeer is het ingesluit: 'n aantal subtropiese grasse, staande hooie, gematigde grasse, lusern (Medicago sativa), korog (Triticale X Secale), oondgedroogde raaigras (Lolium multiflorum), en die tannien-bevattende weidings sainfoin (Onobrychis viciifolia) en skaapburnet (Sanguisorba minor). Digestavloei is gemeet deur gebruik te maak van Yb-asetaat en Cr-EDTA as vastestof- en vloeistofmerkers, onderskeidelik. Rumenammoniakkonsentrasie was eksponensieel verwant aan stikstof(N)-inhoud van die ruvoer, veral bokant 2.5% N in die ruvoer droë materiaal. Rumenfermentasie van tannienbevattende ruvoere het tot laer ammoniakkonsentrasies gelei as rumenfermentasie van ruvoere wat nie tannien bevat het nie. NAN-vloei na die dunderm as 'n verhouding van N-inname het betekenisvol (P ≤ 0.05) verskil tussen ruvoerklasse: 0.97 ± 0.09 vir subtropiese ruvoere, 0.75 ± 0.09 vir gematigde grasse plus lusern en korog, en 1.12 ± 0.08 vir tannien-bevattende ruvoere en gedroogde gras. NAN-vloei as 'n verhouding van N-inname het progressief afgeneem met 'n toename in N-inname by alle nie-tannien ruvoere, en die afname was veral merkbaar by ruvoere met hoë totale (meer as 3%) en/of hoë oplosbare N. NAN-verdwyning in die dunderm as 'n verhouding van NAN wat na die dunderm gevloei het, het betekenisvol (P ≤ 0.01) verskil tussen tannien-bevattende ruvoere en subtropiese staande en gesnyde hooie aan die een kant (0.64 ± 0.06), en alle ander ruvoere aan die ander kant (0.76 ± 0.02). NAN-verdwyning as 'n verhouding van N-inname het toegeneem, en wel in die volgorde: gematigde grasse plus lusern en korog, subtropiese staande en gesnyde hooie, subtropiese grasse, tannien-bevattende ruvoere, en gedroogde gras

Keywords: Absorption, digestion, forage, non-ammonia nitrogen, sheep.