Polyploidy affects fillet yield, composition, and fatty acid profile in two-year old, female rainbow trout, Oncorhynchus mykiss

Gonadal development in fish is a dominant physiological process that alters growth and fat metabolism, thereby affecting fillet quality. Sterile, triploid (3 N) female rainbow trout are generated by pressure-induced shock of zygotes (3NP), and by crossing a diploid (2 N; fertile) female and a tetraploid (4 N; fertile) male to produce triploid offspring 100% of the time (3NC; sterile). We have shown female intercross-triploids (3NC) have faster growth rates than pressure-induced triploids (3NP). Using a subset of these animals, we examined fillet yield, texture and fatty acid composition; additionally, fatty acid composition of triglycerides and phospholipids was determined. Variables were measured immediately prior to ovulation of (2 N; fertile) animals. Separable muscle as a percent of whole body weight was higher (P <= 0.05) in 3NC (46.5%) compared with 3NP (43.6%) fish, and both had higher yields than 2 N (38.3%) individuals. Fillets from 3NC fillets contained more (P < 0.05) intramuscular crude fat than 3NP and 2 N fillets (13.4%, 11.2%, 8.17%, respectively). Also, 2 N fillets contained (P <= 0.05) fewer total saturated fatty acids (29.2%) compared to 3NP (33.4%) fillets which in turn, had fewer than 3NC (34.9%) fillets; suggesting diploids that stored SFA were used for egg development. Although 2 N fillets contained more (P <= 0.05) total polyunsaturated fatty acids relative to all fatty acids (PUFA, 28.7%) than 3NC and 3NP fillets (23.6% and 24.8%, respectively), the 3NC had the highest concentration per gram of fillet. 3NC and 3NP muscle had higher (P < 0.05) levels of C12:0, C14:0, compared to 2 N. Fatty acids, C16:0 and 16:1, were highest (P <= 0.05) in 3NC, and 2 N muscle contained more (P <= 0.05) C22:6n3, C20:3n6 and C18:1n9c compared to 3NC and 3NP. Linoleic acid (18:2n6c) was highest in 2 N followed by 3NP and 3NC muscle (P > 0.05). Thin Layer Chromatography plates were used to separate lipid classes and to evaluate the fatty acid composition of each lipid class. Ploidy did not affect (P 0.05) fatty acids present in triglyceride and phospholipids. Albeit, triglycerides had higher (P < 0.10) levels of C16:1, C18:1n9c, C18:2n6c, C18:3n3 and C22:1n9 compared to the phospholipids; whereas phospholipids contained higher levels of C16:0, C20:4n6, C20:5n3, and C22:6n3. Notably, phospholipids contained 3 times more C22:6n3 docosahexaenoic acid (DHA) compared to triglycerides. Overall, intercross-triploids (3NC) exhibited superior growth and fillet yields and higher concentrations of intramuscular crude fat compared to 3NP and 2 N females, fillet texture and fatty acid profile were not different, with the exceptions of C18:2n6c, C16:0, and C16:1.