Moran E T
J Nutr. 1985 May;115(5):665-74. doi: 10.1093/jn/115.5.665.
Starch is the main carbohydrate in the food of poultry. Starch granules are digested by pancreatic alpha-amylase in the small intestine. Intestinal villi have enterocytes that project microvilli with a fibrous glycocalyx from the surface. These fine structures are envisaged to entrap water that is mixed with mucin from nearby goblet cells to form the "unstirred water layer." Maltose, maltotriose and alpha-limit dextrins must diffuse across this first barrier to absorption to be hydrolyzed by maltase and sucrase-isomaltase immobilized at the membrane; however, the resultant glucose, once formed, accrues at the surface to provide a concentration advantage. Fowl adjust to changes in dietary starch by altering the amount of amylase released, intestinal surface area and enterocyte carbohydrase concentration. Enterocytes arising during embryonic development have no carbohydrases and are not involved with glucose absorption, but they appear to be specialized for maternal immunoglobin transfer in ovo. Embryonic villi are stimulated by transfer activity, and their growth depends on enterocytes arising from the crypt. Mature crypt cells are capable of digestion-absorptive activities and dominate the villus shortly after the chick hatches when yolk sac reserves are depleted.
淀粉是家禽食物中的主要碳水化合物。淀粉颗粒在小肠中被胰腺α-淀粉酶消化。肠绒毛有肠上皮细胞，这些细胞从表面伸出带有纤维状糖萼的微绒毛。这些精细结构被设想为截留与附近杯状细胞分泌的粘蛋白混合的水，从而形成“未搅动水层”。麦芽糖、麦芽三糖和α-极限糊精必须扩散穿过这第一道吸收屏障，才能被固定在膜上的麦芽糖酶和蔗糖酶-异麦芽糖酶水解；然而，一旦形成的葡萄糖会在表面聚集，从而提供浓度优势。家禽通过改变淀粉酶的分泌量、肠表面积和肠上皮细胞碳水化合物酶浓度来适应日粮淀粉的变化。胚胎发育过程中产生的肠上皮细胞没有碳水化合物酶，不参与葡萄糖吸收，但它们似乎专门用于在卵内传递母体免疫球蛋白。胚胎绒毛受到传递活性的刺激，其生长依赖于隐窝产生的肠上皮细胞。成熟的隐窝细胞具有消化吸收活性，在雏鸡孵化后不久，当卵黄囊储备耗尽时，它们在绒毛中占主导地位。
