Comparison of growth and carcass composition of diploid and triploid pansize rainbow trout (Oncorhynchus mykiss) under farm conditions

The growth performance and carcass parameters of female diploid and triploid pansize rainbow trout (Oncorhynchus mykiss) were compared under standardized rearing conditions at a commercial trout farm. In total 15 000 diploid and 15 000 triploid fingerlings were included in the experiment. Performance comparison was carried out when fish reached the age of 41 weeks and lasted till fish were 75 weeks old. During this period survival and growth were recorded as well as feed consumption. At the 66(th) and 75(th) week, 52 fish from each ploidy-group were slaugthered and the following parameters were recorded: body weight, -width -height and -length as well as the weight of offal, gonads, head and fins. Net carcass weight was determined as body weight at slaughter minus weight of offal, head and fins. At slaughter, a triploidisation success of 80.8% was determined in the triploid slaugther group. Ploidy status did not effect growth or survival rates. With 1.01 kg feed, more feed was consumed to achieve one kg body mass increase in the triploid group than in the diploid group (0.90kg). Diploid fish appeared to be more stocky in shape than triploids and had a significantly higher percentage of offal. At both slaughtering dates the triploid fish showed a significantly higher net carcass percentage.