Dintzis F R, Laszlo J A, Nelsen T C, Baker F L, Calvert C C
National Center for Agricultural Utilization Research, ARS, USDA, Food Physical Chemistry, Peoria, IL 61604, USA.
J Anim Sci. 1995 Apr;73(4):1138-46. doi: 10.2527/1995.7341138x.
Mineral bioavailability is related to the activity of the free ion or small-ligand metal ion complexes present in gastrointestinal (GI) tract digesta. Therefore, it is necessary to distinguish between total ion and free-ion/small-ligand complexes (referred to simply as "free") concentrations. Free and total cation concentration in pig digesta from various GI locations were determined. Free ions were operationally defined as those that passed through a 1,000 molecular weight cutoff filter. To test the effect of dietary supplementation on free ion concentrations, pigs were fed either basal diets of corn bran, corn grits, and soybean meal (10, 67, and 20 weight percent, respectively) or basal diets containing added Ca, Zn, Fe, and Cu. In addition, the Ca and K content of corn bran fragments retrieved from digesta was determined by energy dispersive x-ray analysis to examine whether this dietary fiber preferentially absorbed minerals, thus reducing mineral bioavailability. Free cation concentrations, expressed as a percentage of the total, averaged over all locations for both diets were: Na, 86%; K, 96%; Ca, 11%; Mg, 40%; Zn, 5%; Fe, 4%; and Cu, 11%. For Ca, Mg, Zn, and Cu, the free:total cation concentration ratios differed (P < .05) between upper and lower GI tract. Mineral supplementation did not alter free:total ratios of any ion in the GI tract. For supplemented diets, mineral concentrations generally were higher throughout the GI tract, as were concentrations of free Ca. Free concentrations of Zn and Cu in the jejunum and ileum were higher (P < .01) with supplemented diets.(ABSTRACT TRUNCATED AT 250 WORDS)
矿物质生物利用率与胃肠道消化物中存在的游离离子或小分子配体金属离子络合物的活性有关。因此，有必要区分总离子浓度和游离离子/小分子配体络合物（简称为“游离”）浓度。测定了来自猪不同胃肠道部位消化物中的游离和总阳离子浓度。游离离子在操作上被定义为能通过截留分子量为1000的滤膜的离子。为了测试日粮添加物对游离离子浓度的影响，给猪饲喂玉米麸、玉米糁和豆粕的基础日粮（分别占体重的10%、67%和20%）或添加了钙、锌、铁和铜的基础日粮。此外，通过能量色散X射线分析测定了从消化物中回收的玉米麸碎片的钙和钾含量，以检查这种膳食纤维是否优先吸收矿物质，从而降低矿物质生物利用率。两种日粮所有部位的游离阳离子浓度以占总浓度的百分比计平均为：钠，86%；钾，96%；钙，11%；镁，40%；锌，5%；铁，4%；铜，11%。对于钙、镁、锌和铜，胃肠道上部和下部的游离:总阳离子浓度比值不同（P<0.05）。矿物质添加并未改变胃肠道中任何离子的游离:总比值。对于添加矿物质的日粮，整个胃肠道中的矿物质浓度普遍较高，游离钙的浓度也是如此。添加日粮时，空肠和回肠中锌和铜的游离浓度较高（P<0.01）。（摘要截短为250字）
