A total of 540 Japanese quail eggs were assigned to 9 treatments of 4 replicates to investigate the effect of in ovo injection of threonine (THR) on mucin2 (MUC2) mRNA expression and digestive enzyme activity. Treatments were (non-injected) eggs and those in ovo injected with saline (0.05 or 0.1 ml) with or without THR (5 mg/ml) in two sites (in or under the air sac). On hatch day, 0.05 ml in ovo injected (under the air sac: TUAS) hatchlings were divided into three groups based on NRC recommendations for THR, while all 0.1 ml in ovo injected chicks were removed due to low hatchability. The remaining treatments received the NRC recommended diet until day 10 post-hatch. Treatments had no effect on protease and amylase activities, while TUAS increased MUC2 gene expression. In conclusion, the in ovo injection of THR increased MUC2 gene expression but had no effect on enzyme activity.

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