Rumen ammonia concentrations, and non-ammonia nitrogen passage to and apparent absorption from the small intestine of sheep inge

Author: H.H. Meissner, M. Smuts, W.A. van Niekerk and O. Acheampong-Boateng
Year: 1993
Issue: 3
Volume: 23
Page: 92 - 97

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.


Keywords: Absorption, digestion, Forage, non-ammonia nitrogen, sheep
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