LAUSR

Abstract The experiment was conducted to investigate the effects of protein reduction and valine levels on growth performance, carcass characteristics, protein digestibility and SLC71 gene expression of Japanese quail. A total of 800 one day-old quails were given 8 dietary treatments, such that each treatment was replicated 5 times on 20 quail groups based on a factorial arrangement (4 × 2) in a completely randomized design during 0–35 days of age. Dietary treatments included 24, 22, 20 and 18% crude protein (CP) each supplemented in order to fulfill the valine requirement (100%) and 10% more than the basic requirement (110%). The results showed that daily feed intake, body weight and daily weight gain of Japanese quail insignificantly increased with 110% valine level compared to the 100% level. In the first, second and third weeks, the highest body weight and daily weight gain was obtained in quails fed on 24% dietary CP, although in the fourth and fifth weeks, body weight significantly and daily weight gain insignificantly increased with 24% dietary CP. The weight of the carcass, the digestive organs and protein digestibility were not affected by the experimental diets. The SLC71 expression significantly increased with incremental levels of CP and valine. In conclusion, 24% CP and 110% valine levels had a positive effect on growth performance parameters. The SLC71 expression significantly increased with incremental levels of CP and valine supplementation.