低P飼料給与がめん羊の唾液流量,第1胃水分バランスおよび血液成分に及ぼす影響〔英文〕
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概要
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Six mature sheep fitted with rumen and duodenal cannulae were offered 2times/d of timothy hay and barley. Mineral supplements were added to barley to provide two treatments varying their phosphorus contents (high P: 4g/d; low P: 1.8g/d) but being constant in all other constituents. All sheep received the high phosphorus diet for 15 days and were changed to the low phosphorus diet for 40 days. PEG 4000 was used to determine ruminal water balance. Effects of a reduction in dietary phosphorus on salivary flow, ruminal water balance and plasma composition were examined. Plasma inorganic phosphorus concentrations were slightly affected by changing the high phosphorus diet to the low phosphorus diet. Within 30 days of low phosphorus diet feeding, plasma inorganic phosphorus concentrations significantly dropped and tended to raise up in the following period. Blood urea nitrogen concentrations were significantly dropped immediately after the low phosphorus diet was given and markedly raised from day 30 of low phosphorus diet feeding. Inorganic phosphorus concentrations in particle free ruminal fluid and duodenal fluid were high in sheep fed the high phosphorus diet and significantly decreased in animals fed the low phosphorus diet. The sudden fall of phosphorus concentrations in particle free ruminal fluid might become a better index for indicating suboptimal phosphorus status rather than a plasma inorganic phosphorus concentration. Ruminal dilution rate decreased from 11.3%/h (high P) to 8.8, 8.6 and 7.1%/h (low P) whereas ruminal liquid volume was unaffected by the level of phosphorus intake (high P: 8.21; low P: 7.8, 8.5 and 9.31). Since a dilution rate expresses a ratio of ruminal fluid outflow to the liquid volume, the reduced dilution rate found in the present study represents the lowered of ruminal fluid outflow. The ruminal fluid outflow, ruminal phosphorus outflow and the estimated salivary flow(ruminal fluid outflow-water intake) tended to be decreased, indicating a reduction in dietary phosphorus intake. In conclusion, under suboptimal phosphorus status, phosphorus loss might be prevented by reducing the amount of salivary flow, affecting on ruminal water balance.
- 公益社団法人 日本畜産学会の論文