Comparison of energy metabolism during the growing period in quail lines selected for body weight

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Abstract
1. The present study was conducted to compare body weight, daily weight gain, relative growth rate, food intake, food conversion efficiency, abdominal fat weight, thyroid weight, plasma T4 concentration, body temperature, oxygen consumption, carbon dioxide production and heat production among three Japanese‐quail lines selected for body weight: a random bred line (RR) and lines for large (LL) or small (SS) body weight. 2. T4 concentration increased in the order SS, RR, LL in both sexes and did not vary significantly between sexes; the SS line had a significantly higher value than that of the LL line. 3. The body temperatures of SS, RR and LL lines were 42.45, 42.03 and 41.25°C in males, and 42.7, 42.03 and 41.63°C in females. 4. The oxygen consumptions of SS, RR and LL lines were 63.4, 46.0 and 43–8 ml/kgW0.75 min. in males, and 61.4, 44.8 and 37.2 in females. The value for SS was significantly higher than those of RR and LL lines in both sexes (P< 0.01). The carbon dioxide productions of SS, RR and LL lines were 31.8, 33.8 and 27–3 ml/kgW075 min. in males, and 31.2, 31.9 and 27.3 in females. In both sexes, that of the LL line was significantly lower than those of the SS and RR lines (P< 0–01). 6. The heat productions of SS, RR and LL lines were 1.178, 0.994 and 0.842 k]/kgW01b min. in males, and 1.142, 0.879 and 0.736 in females. In both sexes, the heat production of the SS line was higher than those of the RR and LL lines (P< 0–01). 7. It was demonstrated that selection for body weight in Japanese quail was accompanied not only by changes in growth rate and conversion efficiency but also by changes in thyroid function and energy metabolism.