7-35日龄羔羊胃肠胃蛋白酶、凝乳酶、乳糖酶活性与其 mRNA 相对表达量和胃肠发育的关系研究

A Study on Relationships between the Activities of Repsin,Chymosin,Lactase and Their mRNA Relative Expressional Volumes and Development of the Stomach and Intestines of 7-35 Day Old Lambs

先后选取56只初生体重为（3360±338）g 的小尾寒羊公羔,随机分为14组（每组 n ＝4）,从4日龄起分别饲喂牛奶粉代乳和鱼粉代乳（各28只）,并在第21日龄将饲喂牛奶粉代乳和鱼粉代乳的羔羊各8只转喂开食料.分别在7,14,21,28,35日龄将各组扑杀,取皱胃和十二指肠组织,测定皱胃胃蛋白酶、凝乳酶和十二指肠乳糖酶活性以及相应 mRNA 相对表达量,以研究饲喂不同代乳及开食料条件下7~35日龄羔羊3种消化酶与其 mR-NA 相对表达量和胃肠发育的关系.结果表明,新生羔羊皱胃组织中凝乳酶活性随日龄平均每天降1．3 U/g （r 2＝0．92,P ＜0．05）；而胃蛋白酶活性与日龄相关性低；十二指肠组织中的乳糖酶活性随日龄平均每天降低0．044 U/g （r 2＝0．75,P ＞0．05）.羔羊胃肠组织中的胃蛋白酶、凝乳酶、乳糖酶活性与相应 mRNA 相对表达量间的相关性差,胃蛋白酶与凝乳酶 mRNA 表达量随日龄呈高－低－高波动,而乳糖酶变化不显著.饲喂鱼粉代乳时羔羊的胃蛋白酶、凝乳酶活性降低,皱胃7日龄时重量为（36．0±3．0）g,35日龄时为（38．3±5．4）g,生长停滞.21日龄羔羊改喂开食料时对于原先饲喂牛奶粉代乳羔羊的胃蛋白酶、凝乳酶、乳糖酶活性影响不显著,但胃肠增重和日增重减少,而原先饲喂牛奶粉代乳羔羊的凝乳酶、乳糖酶活性呈降低趋势,对胃肠增重和日增重影响则明显.由本试验得出结论,羔羊胃肠胃蛋白酶活性与日龄相关性低,而凝乳酶和乳糖酶活性随日龄降低；羔羊代乳的性质对羔羊后期的消化、生长都有一定的影响；羔羊鱼粉代乳的消化障碍可能主要是由于皱胃发育停滞而非小肠消化障碍.

Fifty six head of Small-tail Han lamb with body weight of （3 360±338）g were selected in ex-periment and were divided randomly into 14 groups （n =4,in each group）.From 4 day old the lambs were fed with milk powder substitute （MPS）（n =28）or fish meal substitute （FMS）（n =28）respectively,and from 21 day old,8 of lamb fed with MPS or FMS were turned to be fed with starter ration respectively. Each group of lamb at 7,14,21,28 and 35 day old was sacrificed to take the abomasum and duodenum tis-sue,measuring the activities of the pepsin,chymosin and lactase and the corresponding relative expression of mRNA,for studying the development of 3 digestive enzymes of lamb fed with MPS,FMS and starter ra-tion respectively.The result showed that in abomasum or duodenum tissue of newborn lamb the activities of the chymosin and lactase were decreased with the age of lamb by 1.3 U/g （r 2 = 0.92,P ＆lt; 0.05）or 0.044 U/g （r 2 =0.75,P ＆gt;0.05）respectively,but the pepsin activity was weakly related with the age.The relationships be-tween the activities of the pepsin,chymosin and lactase and thier corresponding relative expression of mR-NA was poor,the mRNA expressions of the pepsin and chymosin were fluctuated by high-low-high with the age,however the activity of lactose was not significantly changed with the age of lamb.When FMS was fed,the activities of pepsin,and chymosinwere decreased,the weight of abomasum was （36.0 ±3.0）g at 7 day old of lamb,and was （38.3±5.4）g at 35 day old,suggesting a growth retardation.Turning to starter ration at 21 days of lamb fed priviously with MPS did not significantly affect the activities of the pepsin, chymosin and lactase.But the abomasum and duodenum and daily weight gains of the lambs reduced.Fur-thermore,the activities of pepsin,chymosin and lactase in the milk substitutes,which were fed priviously to the lambs,tended to declining which affected obviously abomasum and duodenum and daily weight gains of the lambs.It is concluded that the pepsin activity is weakly related with the age of lamb,but the activities of chymosin and lactase were decreased with the age;the milk substitutes may affect the latter digestion and growth of lamb;the digestive obstruction on FMS of lamb may mainly be because of the retardation of abo-masum rather than the digestive obstruction of small intestine.