The effects of dietary ascorbic acid supplementation on collagen and amino acid concentrations in Japanese quails exposed to heat stress
Husnu Erbay BARDAKCIOGLU
A considerable body of data exists regarding the role of vitamin C in mammalian physiology; however, there are no data about the effects of dietary ascorbic acid supplementation on collagen concentrations and amino acid levels in animals exposed to heat stress. The present study investigated the effects of supplementary ascorbic acid intake on collagen concentrations in the brain and heart tissue in Japanese quails. In addition, glycine, glutamine, histidine, asparagine, and serine contents in the livers of the same animals were measured. Japanese quails were allocated into 4 groups, each of which was exposed to heat stress (34.8 ± 1.25 °C) for 75 days. Control animals were fed a basal diet, while animals in the experimental groups were fed a basal diet supplemented with 150, 250, or 500 mg of L-ascorbic acid kg-1 of diet. Compared to the control group, mean collagen concentration in brain tissue significantly (P < 0.05) increased only in Japanese quails given 250 mg of L-ascorbic kg-1 of diet. On the other hand, heart tissue collagen content in the quails fed vitamin C did not significantly increase; in fact, the collagen content in the group fed 500 mg of L-ascorbic acid kg-1 of diet significantly decreased (P < 0.01). Amino acid content in the liver significantly increased in the group fed 150 mg of L-ascorbic acid kg-1 of diet (P < 0.01 for serine and P < 0.001 for the others).
In conclusion, vitamin C had profound effects on collagen synthesis and amino acid metabolism in Japanese quails subjected to heat stress. Results of the present study also indicate that addition of high-dose dietary vitamin C-higher than 250 mg kg-1 of diet-may have detrimental effects in quails exposed to heat stress.