Effects on Nitrogen Kinetics in Sheep of the Supplementation of Sodium Propionate and Sodium Acetate to the Diet

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  • SUTOH Madoka
    Department of Animal Physiology, National Institute of Animal Industry
  • OBARA Yoshiaki
    Department of Animal Physiology, National Institute of Animal Industry
  • MIYAMOTO Susumu
    Department of Animal Physiology, National Institute of Animal Industry

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Other Title
  • 飼料へのプロピオン酸ナトリウムおよび酢酸ナトリウム添加がメン羊の体内窒素動態に及ぼす影響
  • シリョウ エ ノ プロピオンサン ナトリウム オヨビ サクサン ナトリウム テ

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Three mature wethers fitted with rumen fistulas were used to investigate the effects on nitrogen kinetics of sodium propionate and sodium acetate added to their diet. The wethers were fed at 12 equal intervals daily in sequence on (1) crushed lucern hay cubes (basal diet) with sodium propionate, (2) basal diet only and (3) basal diet with sodium acetate. Supplemented energy as sodium propionate and sodium acetate were both 5.1% of gross energy in the basal diet. The isotope dilution method, with a single injection of [15N] urea into blood and [15N] ammonium chloride into the rumen, was used to determine the metabolic rates of nitrogen in plasma urea and ruminal ammonia. When wethers were fed the diet with sodium propionate, the concentration and irreversible loss rate of ruminal ammonia significantly decreased relative to when they were fed the basal diet. The production rate of ruminal ammonia from dietary and endogeneous sources, except for urea, and nitrogen transfer rates from ruminal ammonia to plasma urea also decreased. The effect of supplementing sodium acetate to the diet on these kinetics of ruminal ammonia was smaller than that of sodium propionate. The concentration of plasma urea and urinary urea excretion significantly decreased when wethers were fed the diet with both VFA salts, though no clear change was observed in the transfer rate of plasma urea N into the digestive tract. The nitrogen excretion in urine was significantly reduced by the supplementation of both VFA salts, but nitrogen retention tended to increase only when wethers were fed the diet with sodium propionate. It is concluded that the supplementation of sodium propionate at the level used in this experiment decreased urinary urea excretion but did not affect urea recycling via the rumen. The smaller response of nitrogen kinetics to sodium acetate compared with sodium propionate would be associated with sodium acetate's weaker effect on ruminal ammonia production.

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