本试验选择离体犊牛小肠上皮细胞，以细胞增殖率和葡萄糖吸收率作为细胞生长发育与功能成熟的指标，研究了胰岛素与胰岛素样生长因子-I（IGF-I）对细胞生长发育的影响。结果表明，胰岛素浓度为10μg/ml时，明显促进小肠上皮细胞的增殖和对葡萄糖的吸收，浓度达到50μg/ml时则抑制细胞的增殖和吸收（P<0.01）。IGF-I浓度为100ng/ml时，对促进小肠上皮细胞增殖和吸收葡萄糖的作用最强（P<0.01），但100ng/ml、500ng/ml和1000ng/ml三种不同浓度的IGF-I对刺激细胞增殖和提高吸收功能无显著差异（P>0.05）。

This study examined the effects of milk protein pre-hydrolyzation on the crypt cell proliferation and morphological alterations in the small intestine in neonatal piglets. The newborn unsuckled Erhualian piglets were bottle-fed for 3 days with cow milk formula or pre-hydrolyzed cow milk formula. When compared with newborn pigs, the height of the intestinal villi decreased by 30-45% in jejunal region inmilk-fed piglets, while no significant change was observed in the intestinal villus height in piglets fed pre-hydrolyzed milk. Microscopic examination showed an atrophy of the intestinal villi and accelerated proliferation of crypt cells in the milk-fed piglets, possibly due to a hypersensitive reaction of the intestine to dietary protein. The results indicate that the nature of dietary protein had a significant effect on the intestinal structure. This finding may have a significant implication in infant care and animal feeding.

To investigate what factors lead to the rapid postnatal tissue growth and functional maturation in the newborn intestine we compared intestinal tissue mass and digestive enzyme activities between newborn unsuckled piglets and piglets bottle-fed for 3 days with either intact porcine colostrum or trypsinized porcine colostrum. Bottle-feeding of colostrum or trypsinized colostrum led to a significant increase in weight and length of the small intestine and a significant increase in mucosal weight of the large intestine. The mucosal protein content in the small and the large intestine and the mucosal DNA content in the large intestine increased significantly following 3-days bottle-feeding of porcine colostrum or trypsinized colostrum. The total mucosal DNA contents in the small intestine of piglets fed colostrums or trypsinized colostrum were, respectively, 39 and 64% greater than that in the newborn unsuckled piglets. The numbers of cells labeled with BrdU in intestinal crypts also increased significantly in piglets fed both diets compared with that of newborns. But a marked increment in villus height was observed only in piglets fed intact colostrum. Brush-border membrane enzymes showed a differential response to the dietary treatment. Bottle-feeding of intact porcine colostrum, but not trypsinized porcine colostrum led to a significant increase in lactase, alkaline phosphatase and aminopeptidase specific activities in the small intestine. In contrast, the specific activity of maltase in the small intestine increased significantly with age irrespective of dietary treatment. These results indicated that genetic and dietary factors are involved in regulating postnatal intestinal development, and porcine colostrum contains a trypsin-labile component which can increase lactase and alkaline phosphatase activities in the newborn intestine.

50 头21日龄断奶的胜利白猪随机分为5组，Ⅰ组（对照组）为基础日粮组；Ⅱ、Ⅲ、Ⅳ组分别为基础日粮+1%、2%、3%小肽营养素；Ⅴ组为基础日粮+2%SDPP。试验期28天。与对照组相比，断奶日粮中添加3%小肽营养素后，仔猪断奶至7周龄平均日增重提高33.91%（P<0.05），料重比下降8.4%（P<0.05），与添加2%SDPP的效果类似。添加小肽营养素后，仔猪十二指肠、空肠、回肠的绒毛长度增加、隐窝深度减小，这种趋势随着小肽营养素添加量的增加而提高。小肽营养素能刺激仔猪断奶后十二指肠食糜乳糖酶、淀粉酶、脂肪酶和胰蛋白酶的活性，以添加3%小肽营养素和2%SDPP效果较好。此外，小肽营养素可促进断奶仔猪免疫系统发育，增加血液中IgG浓度（P<0.05），降低腹泻率（P<0.05）。结果表明，小肽营养素可促进断奶仔猪生产性能及小肠发育，其作用随添加量的增大而提高，添加量以3%最好，并可代替2%SDPP。

本试验以离体犊牛小肠上皮细胞为试验对象，选择细胞增殖率和葡萄糖吸收率作为细胞生长发育与功能成熟的指标，研究了牛初乳的蛋白酶水解产物对细胞生长发育的影响。结果表明，初乳经胃蛋白酶水解处理90分钟后所产生的水解物对离体犊牛小肠上皮细胞有明显的促增殖作用（P<0.01），而初乳经胰蛋白酶处理则不表现促增殖活性。初乳酶解物对促进细胞吸收葡萄糖的作用随着酶解处理时间的延长逐渐增强，初乳经胰蛋白酶水解处理90分钟或经胃蛋白酶水解处理150分钟时的产物对细胞吸收葡萄糖的促进作用分别达到最强（P<0.01）。结果表明，初乳酶解物即小分子蛋白质（肽）具有刺激离体小肠上皮细胞增殖和功能发育的活性。