| Summary: | The aim of this study was to investigate protein requirements for the maintenance and growth of blue-breasted quail (Excalfactoria chinensis) from 7 to 21 days of age. A total of 180 quails, 7 days old, were randomly assigned to 36 cages and for 2 weeks were fed diets with a metabolisable energy concentration of 12.13 MJ/kg and a dietary CP concentration of 125, 150, 175, 200, 225 or 250 g/kg. The average BW per cage and the feed intake per cage were recorded daily. The results showed that quails fed 125 g/kg CP could not maintain their BW and had negative feed efficiency. There were linear and quadratic relationships between CP level and response criteria, including BW, weight gain, feed intake, feed efficiency, final body nitrogen mass and body nitrogen accretion (P < 0.05). The dietary CP requirements, as calculated using a one-slope quadratic broken-line model, were 211 and 202 g/kg according to weight gain and feed efficiency, respectively. The regression equations, on the basis of metabolic BW, of daily weight gain on daily protein intake according to the model were Y = 0.137−2.128(0.113−X) if X < 0.113 and Y = 0.137 if X ⩾ 0.113 (R2 = 0.96, P < 0.001), which meant that the protein requirement for maintenance was 0.049 times the metabolic BW and that to gain 1 g weight quails needed to ingest an extra 0.47 g protein after the maintenance requirement was satisfied. The regression equations, on the basis of metabolic BW, of daily body nitrogen accretion on daily protein intake according to the model were Y = 5.667−76.700(0.119−X) if X < 0.119 and Y = 5.667 if X ⩾ 0.119 (R2 = 0.95, P < 0.001), which meant that quails had to receive an amount of protein equal to their metabolic BW multiplied by 0.045 to satisfy the requirement for maintenance and then ingest an extra 13 g protein to accrete 1 g body nitrogen. In conclusion, growth or protein accretion rates should be regulated according to dietary CP for specific experimental purposes via apportioning protein requirements for maintenance v. growth.
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