Date of Graduation

2015

Document Type

Thesis

Degree Type

MS

College

Davis College of Agriculture, Natural Resources and Design

Department

Animal and Nutritional Sciences

Committee Chair

Patrick B Kenney

Committee Co-Chair

Eugene E Felton

Committee Member

Janet Tou

Abstract

Gonadal development is a dominant physiological process that alters growth and fat metabolism, thereby reducing fillet quality. Sterile, triploid (3N) female rainbow trout, generated by pressure-induced shock of zygotes 30 minutes after fertilization (3NP), are used to eliminate reduced growth and quality associated with gonadogenesis. However, this method does not produce 100% 3N offspring. Crossing a diploid (2N; fertile) female and a tetraploid (4N; fertile) male produces triploid offspring 100% of the time (3NC; sterile). This method is not widely used in the industry because it requires 4N brood stock. The current study examines growth, fatty acid composition, and fillet quality attributes, just prior to ovulation for diploid (2N), pressure-induced triploid (3NP), or naturally-produced triploid (3NC) females. As an indication of growth rate, 3NC (2109.2g) fish were heavier followed by 2N (1826.3g) and 3NP (1524.2g) individuals (p<0.05). Separable muscle as a percent whole body weight was higher (p<0.05) in 3NC (46.5%) followed by the 3NP (43.6%), and both methods of triploid induction were higher compared to the 2N (38.3%) individuals. These measurements indicate that larger fish do not yield the highest proportion of muscle. The 3NC fillets contained more (p<0.05) intramuscular crude fat followed by the 3NP and 2N fillets (13.4%, 11.2%, 8.17%, respectively). Our data demonstrate the inverse relationship between moisture and fat content; moisture content was highest (p<0.05) in the 2N followed by the 3NP and 3NC (72.3%, 68.8%, 66.7%, respectively). Based on relative peak area, 2N fillets contained (p<0.05) fewer saturated fatty acids (SFA, 29.2%) compared to 3NC (34.9%) and 3NP (33.4%) fillets; diploids mobilized stored SFA for egg development. Moreover, 2N fillets contained more (p<0.05) polyunsaturated fatty acids (PUFA, 28.7%) compared to 3NC and 3NP (2.6% and 24.8%, respectively). 3NC and 3NP muscle had higher (p<0.05) levels of C12:0, C14:0, compared to 2N animals. Fatty acids C16:0 and 16:1 were highest (P<0.05) in 3NC compared to other ploidies. Albeit, 2N 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 2N followed by 3NP then 3NC muscle (p<0.05). To determine if fatty acids were preferentially mobilized from triglyceride or phospholipids, TLC plates were used to separate lipid classes; ploidy did not affect (p>0.05) fatty acids present in triglyceride and phospholipids. However, when comparing lipid classes the data indicated that the triglycerides had higher levels of C16:1, C18:1n9c, C18:2n6c, C18:3n3 and C22:1n9 when compared to the phospholipids. While phospholipids contained higher levels of C16:0, C20:4n6, C20:5n3, and C22:6n3. Most notably phospholipids contained 3 times the level of C22:6n3 docosahexanoic acid (DHA) compared to triglycerides. DHA is known for its important role in maintaining the structure and function of cellular membranes. Overall, naturally produced triploids (3NC) exhibited superior growth and fillet yields, and method of triploid production did not affect fatty acid profile of intramuscular lipid stores with the exception of C18:2n6c, C16:0, and C16:1.

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