ヒツジの反芻胃内における in sacco および in vivo 法による非分解性乾草RNA量の測定とその微生物合成量の推定値に及ぼす影響 Measurement of Undegradable Grass Hay Ribonucleic Acid by In sacco and In vivo Methods and Their Effect on the Estimation of Microbial Production in the Rumen of Sheep

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オーチャードグラス乾草を単体給与したヒツジを用いて,乾草RNAの第一胃内分解率を<i>in Sacco</i>および<i>in vivo</i>で調べ,十二指腸に流入する乾草由来RNA(第一胃内非分解性乾草RNA)量を測定した.さらに,このRNA量が,RNAを微生物体マーカーに用いて求められる第一胃内微生物合成量にどの程度の影響を及ぼすかについて検討した.乾草RNAの<i>in sacco</i>分解率,いわゆる第一胃内有効分解率(ED)は,第一胃内分解性(分解率,分解速度)および通過速度から,<i>in vivo</i>分解率は十二指腸に流入する総RNA量と微生物由来RNA量の差から求めた.また,その微生物(細菌+原虫)由来RNA量は,細菌および原虫のマーカーにそれぞれジアミノピメリン酸(2,6-diaminopimeric acid)およびホスファチジルコリン(Phosphatidylcoline)を用い,細菌量および原虫量を求め,それぞれのRNA濃度を乗じて求めた.乾草RNAのEDは平均で79.4%を示し,乾物(49.3%)および粗タンパク質(60.4%)のそれらに比して高かった(P<0.01).一方,乾草RNAの<i>in vivo</i>分解率は平均で95.7%となり,<i>in sacco</i>の値(ED)よりも高かった.これらの分解率を用いて求められる十二指腸流入乾草由来RNAは,<i>in sacco</i>および<i>in vivo</i>でそれぞれ21および4mg/kgBW/dとなり,細菌量(見かけ)に換算するとそれぞれ170および32mg/kgBW/dであった.これら見かけの細菌量の総細菌量(2,513mg/kgBW/d)に占める割合は,<i>in sacco</i>で6.8%,<i>in vivo</i>で1.3%であった.これらの結果から,十二指腸に流入するオーチャードグラス乾草由来RNA量の微生物合成量の算出値に与える影響は比較的小さいものと考えられた.

Four sheep, fitted with ruminal and duodenal cannulas and given only orchardgrass hay, were used for <i>in sacco</i> and <i>in vivo</i> estimation of the ruminal degradation of the hay ribonucleic acid (RNA) and for measurement of duodenal digesta flow. Other four rumen cannulated sheep given orchardgrass hay were used to isolate bacterial and protozoal samples from strained rumen content and to determine the concentration of RNA (purines), diaminopimelic acid (DAPA) and phosphatidylcholine (PC) as markers of rumen microbes. Samples of hay and duodenal digesta were also analyzed for these markers. The degradation characteristics <i>in sacco</i> of hay RNA, dry matter (DM) and crude protein (CP) were measured by incubating hay sample in polyester bags in the rumen. The results were fitted to the exponential equation p=a'+b'{1-e<sup>-c(t-Lt)</sup>}, where p is disappearance for each constituent from the bag after t (h), a' the solubility (washing loss), b' the insoluble but potentially fermentable material, c the constant of degradation rate of b' and Lt the lag time of degradation. Particle outflow rate (k1) from the rumen was estimated using chromium mordated hay. Effective degradability (ED) of each constituent of hay was given by the equation ED=a'+bc/(c+k1)e<sup>-(c+k1)Lt</sup>. Average ED of RNA was 79.4% which was remarkably higher compared to them of DM (49.3) and CP (60.4%). The average flow of DM to the duodenum of sheep was 10.4gDM/kgBW/d. Concentrations of RNA in hay, bacteria, protozoa and duodenal digesta were 5.2, 123.5, 77.5 and 29.8mg/gDM, respectively. DAPA was found only in bacteria (2.0mg/gDM) and duodenal samples (0.4mg/gDM). PC was obtained in protozoa (19.2mg/gDM) and in duodenal digesta (1.9mg/gDM). On the basis of these data, average total RNA (310), DAPA (4) and PC (20mg/kgBW/d) duodenal flow was calculated. The average amounts of bacteria reaching duodenum calculated by DAPA as a marker, and of protozoa calculated by PC, were 1, 829 and 1, 022mg/kgBW/d, respectively. Using these amounts and concentrations of RNA in bacterial and protozoal samples, it was estimated bacterial and protozoal RNA flux to duodenum: 226 and 79mg/kgBW/d, respectively. The sum of bacterial and protozoal RNA was subtracted from the total duodenal RNA flow. The result was assumed as an amount of ruminally escaped RNA with hay origin: 5mg/kgBW/d. Undegraded feed RNA was devided by the intake of RNA with hay (104mg/kgBW/d), expressed as percent (5.0) and subtracted from 100 in order to get rumen degradability <i>in vivo</i> of grass hay RNA: 95.7%. Consequently, the proportions of bacteria amount, estimated from the undegraded hay RNA <i>in sacco</i> and <i>in vivo</i>, to that calculated from the total RNA duodenal flow, were 6.8 and 1.3%, respectively.

収録刊行物

  • 日本畜産學會報 = The Japanese journal of zootechnical science  

    日本畜産學會報 = The Japanese journal of zootechnical science 69(2), 146-153, 1998-02-25 

    Japanese Society of Animal Science

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各種コード

  • NII論文ID(NAID)
    10021726886
  • NII書誌ID(NCID)
    AN00195188
  • 本文言語コード
    JPN
  • 資料種別
    ART
  • ISSN
    1346907X
  • データ提供元
    CJP書誌  J-STAGE 
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