Location: Cool and Cold Water Aquaculture Research
2010 Annual Report
2: Identify physiological basis for variation in, and strategies to improve growth and nutrient utilization in rainbow trout. • 2.a. Identify regulatory mechanisms for nutrient utilization in muscle and liver. • 2.b. Identify genetic variation in expression of regulatory proteins within nutrient signaling pathways.
3: Identify physiological basis for variation in, and strategies to improve reproductive performance in rainbow trout. • 3.a. Identify growth factors that affect final maturation and their signaling pathways. • 3.b. Identify effects of the maturation-inducing hormone MIH, candidate growth factors and signaling pathways on translation of maternal proteins during follicle maturation and in response to fertilization. • 3.c. Identify changes in germ cell transcription of TGF-beta superfamily growth factors during oogenesis and oocyte recruitment with the aid of transgenic trout carrying a green fluorescent protein gene driven by the vasa gene promoter (GFP-vasa).
4: Improve procedures for natural triploid (2Nx4N) production and evaluate their performance. • 4.a. Evaluate performance of natural triploid (2Nx4N). • 4.b. Improve procedures for natural triploid (2Nx4N) production.
Third-generation families (n=98) were hatched from the growth-selected line and are being evaluated for survival, growth, feed efficiency, and fillet yield and quality. Progress was made towards converting this mixed-gender line to an industry preferred all-female line by using a phenotypic marker, failure to release sperm, to identify neomales (i.e., genetic females that produce sperm following hormone treatment) as sires. Fecundity and egg quality attributes were characterized for the females in our growth-selected and control lines to determine if selection for improved growth affects reproductive performance.
Multiple physiological responses to stress in fish experimentally exposed to 5 different stressors common to the culture environment were measured. This information together with elucidation of genomic responses to these treatments being conducted in project 1930-31000-009 will identify common and disparate components of responses to diverse stressors and thereby lead to identification of markers that can be used to select for fish that can better resist stress.
In vitro incubations of ovarian follicles were used to identify the interactions among 7 members of the TGF-beta superfamily system with sex steroids and gonadotropin in regulating ovarian development. The growth factors had little effect on steroid production or the resumption of meiosis, although a progestin and gonadotropin preparation altered expression of TGF-beta superfamily system genes. These finding support interactions among the hormone systems in fish, as in mammals. Molecular characterization of two genes involved with protein degradation was conducted, with expression of FBXO32 in muscle and intestine being particularly responsive to changes in nutritional status. There is a quadratic relationship between feed intake and feed efficiency, with optimum feed efficiency occurring at 76% of satiation, as well as a quadratic relationship between plasma IGF-I and feed intake, and FBXO32 expression and feed intake, suggesting optimal feed efficiency is associated with slower rates of protein degradation. These findings provide a better understanding of the impact that different feeding strategies have on the metabolic mechanisms that affect growth and feed efficiency in trout.
The value of tetraploid induction is the ability to cross tetraploid fish with normal diploid fish (2 sets) to produce 100% triploid fish (3 sets [tetraploid derived triploids]) which are sterile. Triploids cannot breed with wild fish and also grow faster after the age of gonadal development. To evaluate performance traits of these tetraploid derived triploids sibling tetraploid and diploid rainbow trout families were developed in 2008. This year these animals were crossed to make diploids, tetraploid derived triploids, and pressure induced triploids (industry standard method), for comparing growth, disease resistance, and stress performance among these different types of animals.
Cleveland, B.M., Weber, G.M., Blemings, K.P., Silverstein, J. 2009. Insulin-like growth factor-I treatment and genetic variation affect changes in indices of protein degradation in response to food deprivation in rainbow trout (Oncorhynchus mykiss). American Journal of Physiology - Regulatory Integrative & Comparative Physiology. 297:R1332-R1342. Cleveland, B.M., Weber, G.M. 2010. Effects of insulin-like growth factor-I, insulin, and leucine on protein turnover and pathways that regulate ubiquitin ligase expression in rainbow trout primary myocytes. American Journal of Physiology - Regulatory Integrative & Comparative Physiology. 298:R341-350. Lankford, S.E., Weber, G.M. 2010. Temporal mRNA expression of transforming growth factor-beta superfamily members and inhibitors in the developing rainbow trout ovary. General and Comparative Endocrinology. 166(2):250-258. Leeds, T.D., Silverstein, J., Weber, G.M., Vallejo, R.L., Palti, Y., Rexroad III, C.E., Evenhuis, J., Hadidi, S., Welch, T.J., Wiens, G.D. 0210. Response to selection for bacterial cold water disease resistance in rainbow trout. Journal of Animal Science. 88:1936-1946.