Comparative Study On The Morphological And Functional Growth And Development Of The Small Intestine Of Lambs Weaned At Same Age With Different Body Weight

Many studies have showed that the growth and development of digestive organs is closely associated with the increase of the body weight in lambs and other young animals. However, the body weight of the same lamb breed varies much even raised in the same condition with same weaning age. We hypothesize that the morphological and functional growth and development of the small intestine in the same lamb breed weaned at same age may play a strong role for influencing its body weight. In the present experiment2 groups of cross bred lambs of Altay×Texel(3-month old and 5-month old) both weaned at 3 month age were chosen and divided into 2 sub-groups by the significantly different body weight in each age group, i.e., high body weight group(HBW) and low body weight group(LBW). The blood physiological and biochemical parameters, mucosal morphoemtry, digestive emzymes, SGLT1 and GLUT2 were measured to investigate the relation of the growth and development of small intestine and the body weight increase. The results showed:1. There was no significant difference in blood physiological and biochemical parameters between HBW and LBW lambs(P>0.05), but certain tendency changed with the age increase in lambs with different body weight.2. There was a significant interaction between the body weight and the age regarding the small intestine morphology in lambs weaned at same age but with different body weight at different age(P<0.01). In the duodenum the villi height, crypts depth, mucosa thickness in HBW lambs was deeper than that in LBW lambs(P<0.01),the but the value of V/C was extremely lower than that in LBW lambs(P<0.01). In the middle of the jejunum villi height, crypts depth, tunica mucosa thickness,the value of V/C in HBW lambs were extremely higher than that in LBW lambs(P<0.01).In the ileum villi height, tunica mucosa thickness,value of V/C were extremely higher in HBW lambs than that in LBW lambs(P<0.01),but the crypts depth was extremely lower than that in LBW lambs(P<0.01).3. The activity of digestive emzymes measured by RIA in the duodenum of lambs was different neither between the different body weights nor between the different ages. Only In the duodenum the activity of maltase, lactase,invertase and amylase in the small intestine of HBW lambs was significantly higher than that of LBW lambs(P<0.05);4. the expression of SGLT1 and GLUT2 measured by Western blotting showed that SGLT1 was extremely higher(P<0.01) and GLUT2 was also significantly higher(P<0.05) in HBW lambs than that in LBW lambs in the duodenum; and the expression of SGLT1 in 3-month old lambs was significantly higher(P<0.05) and GLUT2 was extremely higher(P<0.01) than that in 5-month old lambs. In the middle of the jejunum the expression of both SGLT1 and GLUT2 was significantly higher in HBW lambs than that in LBW lambs(P<0.05); the expression of SGLT1 in the jejunum of lambs at age of 3-month old was extremely higher than that at 5-month old lambs(P<0.01), but GLUT2 was not significantly different between ages. In the ileum the expression of SGLT1 was significantly higher(P<0.05) and that of GLUT2 was extremely higher(P<0.01) in HBW lambs than in LBW lambs.It is indicated that the different body weight of the same lamb breed weaned at same age and raising condition was strongly related with the mucosa morphometry, the activity of maltase, lactase,invertase,amylasein the jejunum and ileum, and the expression of SGLT1 and GLUT2 in the entire length of small intestine, suggesting that these could be the candidates of molecular targets for the early selection of the rapid growth and development of lambs, meanwhile, this experiment lays a scientific foundation for the development of the early weaning technology in lambs.