Threonine and glutamine in ovo supplementation affects post-hatch development and expression of genes related to the first line of defense of the intestinal mucosa in broiler chickens.

The study evaluated the effect of supplying threonine (Thr) and glutamine (Gln) in ovo on the performance, intestinal morphometry, and mRNA expression of Muc2 and IgA in the intestine of broiler chickens. On day 17.5 of incubation, fertile eggs were injected into the amniotic fluid according to a completely randomized experimental design with four treatments: 0.9% saline; 35 mg/mL Thr; 35 mg/mL Gln; or Thr + Gln (17.5 mg/mL each). After hatching, the chicks were reared using four replicates of 10 birds per treatment until 21 days of age. Isolated Gln resulted in the highest villus:crypt ratio (V:C), whereas greater villus area and higher number of goblet cells were seen in the birds supplemented with isolated Thr or Thr + Gln. In ovo Thr increased Muc2 relative gene expression in the jejunum. Immunoglobulin A gene expression in the intestinal mucosa was higher in birds receiving either Gln or Thr. No significant differences were observed among treatments for the evaluated performance variables. In conclusion, in ovo supplementation with Thr + Gln can potentially exert trophic effects on the development of the intestinal mucosa. On the other hand, in ovo Gln+Thr reduces the expression of genes related to the protection of the intestinal mucosa. The isolated supply of Thr and Gln might be important for strengthening the protective mechanisms of the intestinal mucosa.