Maintenance ration, protein synthesis capacity, plasma insulin and growth of Atlantic salmon (Salmo salar L.) with genetically different trypsin isozymes

Growth was found to be associated with the changes of trypsin activity in t he pyloric caecal tissues and the level of plasma insulin in Atlantic salmo n (Salmo salar L.). A decrease in trypsin activity accompanied by an increa se in plasma insulin was detected one month before an enhanced growth was o bserved. There were significant relationships between weight specific consu mption rate, plasma insulin levels and fish growth. The correlation of weig ht specific consumption rate was higher with growth rate (R-2=0.7, p < 0.00 01) than with plasma insulin concentration (R-2=0.4, p < 0.0001). When the comparison was made between Atlantic salmon carrying and lacking t he trypsin variant TRP-2*92, the fish with the variant had lower maintenanc e ration (p < 0.05), higher capacity for protein synthesis in the white mus cle (p < 0.02), and a greater ability to utilize the feed at a restricted r ation than the fish without the variant. In Atlantic salmon lacking the var iant, both plasma insulin concentrations and growth rates were significantl y lower (p < 0.05) in the fish fed 0.5% bw day(-1) than those fed 1% bw day (-1). Whilst the growth rates of TRP-2*92 salmon fed the different rations became similar one month after similar levels of plasma insulin were observ ed between them. The TRP-2*92 salmon may be defined as a high protein growt h efficiency fish with low protein turnover rate. Genetic variation in trypsin isozyme pattern affects feed utilization, plas ma insulin levels and growth in Atlantic salmon.