Productive performance, bone characteristics, and intestinal morphology of laying hens fed diets formulated with L-glutamic acid.

This study was conducted to evaluate the effects of L-glutamic acid (Glu) on the productive performance, eggshell quality, bone characteristics, and morphologic parameters of laying hens. Two hundred and forty 53-wk-old Hy-Line W36 laying hens were randomly allocated into 5 treatments, 6 replicates, and 8 birds each. The experimental period was 16 wk. The treatments consisted of a Basal diet (Glu calculated at 2.68%) and 4 L-glutamic acid inclusion levels: 2.88, 3.08, 3.28, and 3.48%. Glu inclusion levels in the hens diet had an increasing linear effect (P < 0.05) on eggshell Ca concentration and bone (tibiotarsus) strength index, and a decreasing linear effect (P < 0.05) on the Seedor index. Serum biochemistry results for total and ionic Ca, inorganic P, and alkaline phosphatase were affected by blood collection time (04:00 Pm, 03:00 Am, and 12:00 Pm) but not by the treatments. Jejunum morphometric variables were not influenced by the treatments except for crypt depth, which demonstrated a quadratic effect (P < 0.05). However, proliferating cell nuclear antigen qualitative immunohistochemical analysis of the jejunum showed more positive nuclei in the villus with the addition of Glu. Both with the basal diet and the lowest Glu inclusion treatment, positive nuclei were observed in the crypts and at the base of the villus, while in the treatments with higher Glu levels, positive cells were common all along the villus mucosa, including its extremity. In conclusion, diets formulated with increased levels of Glu had beneficial effects on eggshell Ca concentration, tibiotarsus structure, and proliferative activity of the jejunum of 69-wk-old laying hens. Therefore, dietary L-glutamic acid can be considered an alternative additive to improve bone characteristics in the productive phase of laying hens.