Wang Y, Waghorn G C, Barry T N, Shelton I D
Department of Animal Science, Massey University, Palmerston North, New Zealand.
Br J Nutr. 1994 Dec;72(6):923-35. doi: 10.1079/bjn19940096.
Fresh Lotus corniculatus containing 27 g extractable condensed tannin (CT)/kg dry matter (DM) and 8 g bound CT/kg DM was fed at hourly intervals to sheep held in metabolism cages to study the effects of CT on nutrient digestion and on metabolism of methionine, cystine and inorganic sulphate in plasma. Polyethylene glycol (PEG) was continuously infused into the rumen of half the sheep to remove the effects of CT. Principal measurements in the two groups were plasma irreversible loss (IRL) rate and interconversions of methionine, cystine and inorganic sulphate using 35S labelling. CT in Lotus corniculatus had no effects on the apparent digestion of cellulose and minerals, slightly depressed DM, organic matter and hemicellulose digestion and markedly reduced the apparent digestion of N (P < 0.01). The concentration of NH3 and molar proportions of iso-butyric acid, iso-valeric acid and n-valeric acid in rumen fluid were markedly increased by the PEG infusion (P < 0.01), whereas total volatile fatty acid concentration and molar proportions of acetic acid, propionic acid and n-butyric acid were not affected. PEG infusion temporarily increased rumen protozoa numbers. CT greatly increased the IRL of plasma cystine (13.1 v. 7.0 mumol/min; P < 0.05) and reduced IRL of plasma inorganic sulphate (36.8 v. 48.1 mumol/min; P < 0.01) but had no effect on methionine IRL. CT increased transulphuration of methionine to cystine (4.37 v. 1.24 mumol/min; P < 0.05), increased cystine entering the plasma from whole-body protein turnover plus absorption from the small intestine (9.34 v. 5.75 mumol/min; P < 0.05) and increased cystine flux to body synthetic reactions (11.89 v. 5.41 mumol/min; P < 0.05). CT had no effect on the proportion of methionine total flux transferred to sulphate (0.05 v. 0.06; P < 0.05), reduced the proportion of methionine flux transferred to body synthetic reactions (0.68 v. 0.86) and markedly reduced the proportion of cystine flux transferred to sulphate (0.09 v. 0.27; P < 0.01). It was concluded that CT in Lotus corniculatus reduced rumen protein degradation and markedly increased utilization of plasma cystine for body synthetic reactions.
给代谢笼中的绵羊每小时饲喂一次新鲜百脉根，其干物质中含27克可提取缩合单宁（CT）/千克干物质（DM）以及8克结合CT/千克DM，以研究CT对营养物质消化以及血浆中蛋氨酸、胱氨酸和无机硫酸盐代谢的影响。将聚乙二醇（PEG）持续注入一半绵羊的瘤胃以消除CT的影响。两组的主要测量指标为血浆不可逆损失（IRL）率以及使用35S标记法测定蛋氨酸、胱氨酸和无机硫酸盐的相互转化。百脉根中的CT对纤维素和矿物质的表观消化率没有影响，略微降低了干物质、有机物和半纤维素的消化率，并且显著降低了氮的表观消化率（P<0.01）。注入PEG后，瘤胃液中NH3的浓度以及异丁酸、异戊酸和正戊酸的摩尔比例显著增加（P<0.01），而总挥发性脂肪酸浓度以及乙酸、丙酸和正丁酸的摩尔比例不受影响。注入PEG使瘤胃原虫数量暂时增加。CT显著增加了血浆胱氨酸的IRL（13.1对7.0μmol/分钟；P<0.05），降低了血浆无机硫酸盐的IRL（36.8对48.1μmol/分钟；P<0.01），但对蛋氨酸IRL没有影响。CT增加了蛋氨酸向胱氨酸的转硫作用（4.37对1.24μmol/分钟；P<0.05），增加了胱氨酸从全身蛋白质周转加小肠吸收进入血浆的量（9.34对5.75μmol/分钟；P<0.05），并增加了胱氨酸向身体合成反应的通量（11.89对5.41μmol/分钟；P<0.05）。CT对转移至硫酸盐的蛋氨酸总通量比例没有影响（0.05对0.06；P<0.05），降低了转移至身体合成反应的蛋氨酸通量比例（0.68对0.86），并显著降低了转移至硫酸盐的胱氨酸通量比例（0.09对0.27；P<0.01）。得出的结论是，百脉根中的CT降低了瘤胃蛋白质降解，并显著增加了血浆胱氨酸用于身体合成反应的利用率。
