THE INFLUENCE OF DIETARY-PROTEIN LEVEL ON BODY-WEIGHT OF JAPANESE-QUAIL LINES SELECTED UNDER HIGH-PROTEIN AND LOW-PROTEIN DIETS

Two experiments were conducted to determine the protein requirement of quail lines (P and T) following _selection for increased 4-wk BW unde r normal-protein (28% CP) and low protein (20% CP) diets, respectively . Quail progeny from Generation 39 breeders were fed diets containing 18, 21, 24, and 27% CP from 0 to 5 wk of age in Experiment 1, whereas in Experiment 2, quail progeny from Generation 79 breeders were fed di ets containing 18, 21, 24, 27, and 30% CP from 0 to 4 wk of age. Quail from the unselected base population (C line) were also included in bo th experiments. Significant line, diet, and line by diet interactions were present in both experiments. At 2 wk of age, T line quail were si gnificantly (P < .05) larger than P line quail across diets, whereas b y 4 wk, BW of P line quail were significantly larger than those of T l ine quail. Across dietary protein levels, quail receiving diets contai ning 24% CP or higher were significantly larger than those receiving t he 18 and 21% CP diets. Quail in both the P and C lines had larger BW with increasing protein levels and an apparent protein requirement bet ween 24 and 27% CP. However, quail in the T line showed no BW response to increased protein levels, indicating that long-term selection for increased BW on a 20% CP diet had altered the protein requirement in t his line. Results indicated that quail populations selected under high -protein environments require such environments for maximum growth, wh ereas populations selected under low-protein environments do not requi re high-protein diets for full expression of their genetic potential f or growth.