Effect of diet type on enhanced intestinal protein synthesis by the gut microflora in the chick

An experiment was conducted to investigate the effect of diet type on enhanced protein synthesis by the gut microflora in the chick intestine. Both germ-free (GF) and conventional (CV) White Leghorn chicks were fed ad libitum from 4 to 14 d of age either a nonpurified diet or a purified diet having 19% crude protein and 12.1 kJ/g metabolizable energy value. At 14 d of age, protein synthesis was measured in duodenum, jejunoileum and ceca after a large dose of L-[4-3H]phenylalanine injected intravenously via a wing vein. The results showed that wet tissue weights for all intestinal sections were significantly greater in CV birds than in GF counterparts with consistently larger differences between the two environments in chicks fed the nonpurified diet than in those fed the purified diet. Protein synthesis in all intestinal sections was significantly enhanced by the presence of gut microflora in terms of both fractional rate (%/d) and absolute rate [mg/(100 g BW.d)]. The effect of diet type on fractional and absolute rates of protein synthesis was most remarkable in ceca where the significant difference between GF and CV states was found only in chicks fed the nonpurified diet but not in those fed the purified diet.