Postnatal developmental changes of the small intestinal villus height, crypt depth and hexose transporter mRNA expression in supplemental feeding and grazing goats

- The feeding system affected the jejunal crypt depth, but not the villus height.
- The villus height increased with age in duodenum, but decreased in jejunum and ileum.
- The crypt depth in jejunal and ileal linearly increased with age in both groups.
- Supplemental feeding is beneficial to activate expression of hexose transporters.

This trial was conducted to investigate the effects of feeding system and age on morphological development (including villus height, crypt depth, and ratio of villus height to crypt depth) and expression of hexose transporters (i.e., SGLT1, GLUT2 and GLUT5) in different segments of the small intestine of goat kids. A total of 40 Liuyang black goat kids were randomly slaughtered at 0, 7, 28, 42, 56 and 70 days of age. There were two feeding systems [i.e., supplemental feeding (S) and grazing (G)] from 28 to 70 days of age. Duodenal, jejunal and ileal tissues were collected to measure the villus height and crypt depth. Mucosa samples were taken to quantify mRNA or protein expression of sodium-dependent glucose-linked transporter-1 (SGLT1), facilitated glucose/fructose transporter 2 (GLUT2), and facilitated glucose transporter 5 (GLUT5). Villus height was not affected (P > 0.05) by feeding system, and crypt depth was only affected (P < 0.001) by feeding system within the jejunum. Moreover, villus height increased (P = 0.006) with increasing age in the duodenum, whereas it decreased as age increased in the jejunum (P = 0.040) and ileum (P < 0.001). Additionally, the jejunal and ileal crypt depth linearly increased (P < 0.001) with increasing age in both S and G groups. The feeding system had a significant effect (P < 0.05) on mRNA expression of SGLT1, GLUT2 and GLUT5 in the intestine, except for GLUT2 expression within the ileum. The mRNA and protein expression of SGLT1 and the mRNA expression of GLUT2 and GLUT5 declined (P < 0.001) with increasing age in the jejunum and ileum. The present results indicate that supplemental feeding at an early age is beneficial to activate expression of SGLT1, GLUT2 and GLUT5 transporters in goats for an improved ability to absorb hexose.