Effects of triploidy on growth and protein degradation during the recovery from feed deprivation in rainbow trout (Oncorhynchus mykiss)

Authors: Cleveland, Beth; Weber, Gregory - Greg

Submitted to: Comparative Biochemistry and Physiology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/15/2013
Publication Date: 5/21/2013
Publication URL: http://handle.nal.usda.gov/10113/57137
Citation: Cleveland, B.M., Weber, G.M. 2013. Effects of triploidy on growth and protein degradation during the recovery from feed deprivation in rainbow trout (Oncorhynchus mykiss). Comparative Biochemistry and Physiology. 166:128-137:dx.doi.org/10.1016/j.cbpa.2013.05.017.

Interpretive Summary: Industry interest in triploid fish for aquaculture production is increasing. Triploid fish, with three sets of chromosomes, are sterile, although only the triploid females have impaired gonad growth, a characteristic that offers several advantages that benefit their use in aquaculture. Understanding the physiological differences between triploids and the more commonly raised diploids (two sets of chromosomes) is critical for defining the mechanisms that impact growth performance and subsequent use of triploids in aquaculture. Since growth is affected by nutrient intake, feed deprivation followed by refeeding is often used as an experimental model to identify mechanisms affected by biological signals that regulate growth and protein utilization. Therefore, diploid and triploid rainbow trout were either continually fed, or exposed to one week of feed deprivation followed by refeeding, and growth rates and indices of protein degradation were determined. Triploid fish demonstrated faster growth recovery during refeeding, especially in terms of increasing length. However, diploids exhibited greater regulation of certain genes involved in protein degradation, suggesting that the ability to regulate protein utilization is affected by ploidy. Further characterizing these mechanisms will contribute to the development of diploid and triploid specific feeding strategies, diet formulations, or husbandry practices that optimize nutrient utilization and growth performance.

Technical Abstract: Identifying physiological differences between diploid and triploid rainbow trout will help define how ploidy affects mechanisms that impact growth and nutrient utilization. In this study juvenile diploid and triploid female rainbow trout (Oncorhynchus mykiss) were either continually fed or fasted for one week, followed by a four week refeeding period and indices of growth and proteolysis-related gene expression were measured. Regardless of feeding treatment, triploids displayed greater feed intake and faster specific growth rates and during refeeding triploids exhibited faster elongation growth than diploids. Proteolysis-related gene expression analysis suggested a lower capacity for protein degradation during the refeeding period, predominantly via reduced expression of ubiquitin ligases, fbxo32 and fbxo25, and autophagy-related genes compared to continually fed controls. In addition, continually fed triploids displayed lower expression of several autophagy-related genes, suggesting faster growth rates were characterized by reduced rates of protein degradation. These data suggest that recovery growth following feed deprivation partially results from a reduced activity of both specific and non-specific proteolytic mechanisms. Additionally, triploids may be better able to recover from feed deprivation than diploids, although this effect appears limited to recovery of skeletal growth rather than somatic tissues.