Growth and Nutrient Metabolisms of A New Backcross Sea Bream, Red Sea Bream×F₁ (Red Sea Bream×Crimson Sea Bream)
—Development of New Sea Bream Seeds by Hybridization-II—

A new backcross sea bream (RF₁), red sea bream (RSB) Pagrus major ×F₁ (RSB ×crimson sea bream Evynnis japonica ), and RSB, weighing 107g on an initial mean body weight, were given a commercial diet at a daily feed intake of 1.2% body weight for 80 days. The RF₁ steadily grew but showed lower final mean body weight, feed efficiency, protein efficiency ratio, apparent protein retention and final gastral and enteral organ-somatic indices than the RSB. The RF₁, on the other hand, had higher apparent lipid retention, hepatosomatic index, lipid contents of abdominal cavity, carcass and hepatopancreas, and enzyme activities of hepatic aspartate aminotransferase, alanine aminotransferase, glucose-6-phosphate dehydrogenase, and fructose-1,6-bisphosphatase on the final day of the rearing period. No significant differences between RF₁ and RSB were found in final hematocrit value, hemoglobin content, plasma total protein level, and blood glucose. These results indicated that RF₁ was characterized by slightly lower growth performance than RSB, due to small digestive organs and excessive amino acid utilization for energy expenditure, gluconeogenesis, and lipid synthesis.

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