Edmonds M S, Baker D H
University of Illinois, Urbana 61801.
J Anim Sci. 1987 Dec;65(6):1538-52. doi: 10.2527/jas1987.6561538x.
Weanling pigs were fed a 30% crude protein (CP) diet for 18 d and then assigned to one of three regimens for either 4 or 8 d: 1) fasting, 2) 3% CP, i.e., maintenance or 3) 30% CP after which they were bled, then sacrificed for tissue assessment. Relative to pigs fasted or fed 30% CP, feeding 3% CP resulted in decreased urea-N and NH3-N excretion in the urine. Arginase and ornithine transcarbamoylase (OTC) activities in liver, and arginase activity in kidney cortex were markedly lower in pigs fed 3% CP compared with those either fasted or fed 30% CP. Hepatic arginase and OTC, however, were higher in fasted pigs than in those fed 30% CP. Pigs fed 3% CP had much lower levels of free threonine, tyrosine, cystathionine, taurine and branched-chain amino acids in plasma, liver, kidney, muscle and brain than fasted pigs or those fed 30% CP. Threonine concentration in brain, liver, muscle and plasma increased as length of the fast increased. Fasted pigs had decreased free alanine levels in plasma, and decreased free serine levels in plasma and liver when compared with fed pigs. Inter-organ comparisons provided evidence that both alanine and serine were important gluconeogenic amino acids during fasting. In general, free amino acid levels in brain were similar between fasted pigs and those fed 30% CP. Fasting for 8 d caused a 10-fold elevation in urinary taurine excretion relative to that observed for 4-d fasted pigs.
将断奶仔猪饲喂含30%粗蛋白（CP）的日粮18天，然后将其分配到三种日粮方案之一，持续4天或8天：1）禁食；2）3%CP，即维持日粮；3）30%CP，之后采血，然后处死以进行组织评估。与禁食或饲喂30%CP的猪相比，饲喂3%CP导致尿液中尿素氮和氨氮排泄减少。与禁食或饲喂30%CP的猪相比，饲喂3%CP的猪肝脏中的精氨酸酶和鸟氨酸转氨甲酰酶（OTC）活性以及肾皮质中的精氨酸酶活性显著降低。然而，禁食猪的肝脏精氨酸酶和OTC活性高于饲喂30%CP的猪。与禁食猪或饲喂30%CP的猪相比，饲喂3%CP的猪血浆、肝脏、肾脏、肌肉和大脑中的游离苏氨酸、酪氨酸、胱硫醚、牛磺酸和支链氨基酸水平要低得多。随着禁食时间延长，大脑、肝脏、肌肉和血浆中的苏氨酸浓度升高。与采食猪相比，禁食猪血浆中的游离丙氨酸水平降低，血浆和肝脏中的游离丝氨酸水平降低。器官间比较表明，丙氨酸和丝氨酸在禁食期间都是重要的糖异生氨基酸。一般来说，禁食猪和饲喂30%CP的猪大脑中的游离氨基酸水平相似。与禁食4天的猪相比，禁食8天导致尿牛磺酸排泄量增加10倍。
