Mesbah M M, Asplund J M
J Nutr. 1984 Aug;114(8):1363-9. doi: 10.1093/jn/114.8.1363.
A 4 X 4 Latin square design with an extra period was used to determine the influence of different levels of valine (Val) on the nitrogen metabolism of sheep receiving all nutrients by infusion. Glucose, amino acids and water-soluble vitamins were introduced in the jugular vein while inorganic nutrients and volatile fatty acids were given intraruminally. The amino acid mixture contained 1, 3, 5 or 7 g of Val with varying amounts of glycine (Gly) to balance the nitrogen level. The infusion in the extra period was isonitrogenous but contained no Val. When Val was omitted from the infusion, nitrogen balance (NB) was significantly reduced and plasma urea nitrogen (PUN) was significantly increased compared with all levels of added Val. The level of Val infusion that supported the numerically highest NB and the lowest PUN and urinary urea nitrogen (UUN) was 3 g/day, although NB and PUN, at all levels of added Val, were not statistically different. Plasma free Val increased abruptly at infusion levels above 3 g of infusion. It was concluded that Val is metabolically essential for the sheep and the best estimate of the requirements would be 200 mg/(kg body weight)0.75 per day in animals of this age and sex.
采用带有一个额外周期的4×4拉丁方设计，以确定不同水平的缬氨酸（Val）对通过输注获取所有营养物质的绵羊氮代谢的影响。葡萄糖、氨基酸和水溶性维生素经颈静脉输注，而无机营养物质和挥发性脂肪酸则经瘤胃内给予。氨基酸混合物含有1、3、5或7克缬氨酸，并搭配不同量的甘氨酸（Gly）以平衡氮水平。额外周期的输注含氮量相同，但不含缬氨酸。当输注中省略缬氨酸时，与所有添加缬氨酸的水平相比，氮平衡（NB）显著降低，血浆尿素氮（PUN）显著升高。支持数值上最高的氮平衡以及最低的血浆尿素氮和尿尿素氮（UUN）的缬氨酸输注水平为3克/天，不过，在所有添加缬氨酸的水平下，氮平衡和血浆尿素氮在统计学上并无差异。当输注水平高于3克时，血浆游离缬氨酸会突然增加。研究得出结论，缬氨酸对绵羊具有代谢必需性，对于该年龄和性别的动物，最佳需求量估计为每天200毫克/（千克体重）^0.75 。
