Effect of Nitrogen Fertilization on the Yield, Chemical Composition and In Vitro Digestibility of Green Panic Plant Fractions

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  • FLEISCHER Joseph Edmund
    Department of Animal Science, Faculty of Agriculture, Kyushu University:(Present address) University of Ghana
  • MASUDA Yasuhisa
    Department of Animal Science, Faculty of Agriculture, Kyushu University
  • GOTO Ichiro
    Department of Animal Science, Faculty of Agriculture, Kyushu University

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Other Title
  • 窒素施肥量がグリーンパニックの植物体各部の重量,化学組成およびin vitro乾物消化率に及ぼす影響
  • 窒素施肥量がグリーンパニックの植物体各部の重量,化学組成およびin vitro乾物消化率に及ぼす影響〔英文〕
  • チッソ セヒリョウ ガ グリーン パニック ノ ショクブツタイ カクブ ノ ジ

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Abstract

A field experiment was conducted to study the effects of nitrogen levels and regrowing period on the dry matter yields, changes in the proportions of forage component fractions, chemical composition and in vitro dry matter digestibility (IVDMD) of these fractions as they affect the nutritive value of the whole forage. The species used in the experiment was green panic (Panicum maximum var. trichoglume cv. Petrie). A 5×4 factorial design in triplicate of five nitrogen levels and four regrowth periods was employed. The nitrogen levels were 0, 14.30, 28.60, 42.90 and 57.20gmN per are per day ; and regrowing periods were 2, 4, 6 and 8 weeks respectively. Dry matter yield increased with increasing regrowing period (p<0.01) as well as increasing nitrogen level (p<0.01). Proportions of green leaves decreased while those of dead leaves and stems (including leaf sheaths and inflorescence) increased with increasing regrowing period. No significant differences were found among nitrogen levels. Nitrogen content increased in all plant fractions with increasing nitrogen levels (p<0.01) but decreased with increasing regrowing period (p<0.01). Green leaves had the highest nitrogen content ; stems had the lowest nitrogen content with dead leaves being intermediate. In all the plant fractions all the cell wall constituents decreased with increasing nitrogen levels but increased with increasing regrowing period. Green leaves had lower cell wall constituents than stems, and dead leaves had either lower or almost the same cell wall contituents as the stems. In vitro dry matter digestibility (IVDMD) of all the component fractions decreased with increasing regrowing period (p<0.01) ; these decreases were 0.71%, 0.29% and 0.81% unit per day for whole forage, green leaves and stems respectively. IVDMD was not affected by nitrogen levels partly because no difference in the proportion of plant fractions among nitrogen levels was observed. It was suggested therefore, that the effect of nitrogen level on digestibility might be limited to situation where an increase in nitrogen content is also accompanied by a large decrease in the cell wall constituents. A very high and negative correlation was found between the cell wall constituents of whole forage or any of its component fractions and their respective IVDMD. Also the correlation between proportion of stems and dead leaves and whole forage IVDMD was negative but that with green leaves was positive.

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