Greene L W, Webb K E, Fontenot J P
J Anim Sci. 1983 May;56(5):1214-21. doi: 10.2527/jas1983.5651214x.
Eighteen wether lambs, surgically equipped with abomasal and ileal cannulae, were used in two metabolism trials. Two levels of dietary Mg (.1 and .2%) and three levels of K (.6, 2.4 and 4.8%, dry basis) were fed with a 2 x 3 factorial arrangement. Each trial consisted of a 10-d preliminary period, a 7-d collection of feed, feces and urine for determining mineral balance and a 6-d sampling of feed, abomasal and ileal fluid and feces to determine flow and site of mineral absorption. Magnesium absorption occurred before the small intestine. Feeding 2.4 and 4.8% K decreased (P less than .05) Mg absorption by 24.4 and 61.2%, respectively. Preintestinal absorption of Mg was depressed linearly with increases in dietary potassium. Larger amounts of Mg flowed to the small intestine and were excreted in the feces when the high level of Mg was fed. A net secretion of Mg into the small intestine followed by a small amount of Mg absorption in the large intestine was also found. Serum Mg was depressed 7 and 10% when diets containing 2.4 and 4.8% potassium were fed, respectively. Magnesium level did not affect K absorption or balance. Potassium absorption, retention and urinary excretion increased (P less than .05) with increasing K level. Animals fed the low K diet had a negative absorption of K preintestinally with the small intestine being the main site of absorption. Increasing K level resulted in approximately equal amounts of K being absorbed in the stomach and small intestine.
18只安装了真胃和回肠瘘管的阉公羊被用于两项代谢试验。采用2×3析因设计，饲喂两种水平的日粮镁（0.1%和0.2%）和三种水平的钾（0.6%、2.4%和4.8%，干基）。每项试验包括10天的预试期、7天收集饲料、粪便和尿液以测定矿物质平衡，以及6天采集饲料、真胃液、回肠液和粪便以测定矿物质吸收的流量和部位。镁的吸收在小肠之前发生。饲喂2.4%和4.8%的钾分别使镁的吸收降低（P<0.05）24.4%和61.2%。随着日粮钾含量的增加，镁的肠前吸收呈线性下降。饲喂高镁水平日粮时，更多的镁流入小肠并随粪便排出。还发现有镁净分泌到小肠，随后在大肠中有少量镁被吸收。分别饲喂含2.
