The high burden of natural resources for agriculture activities requires the development of the technologies and strategies that allow for more sustainable production. One of the main resources used in the aquaculture production is the feed, representing the highest cost in the production chain, ranging between 40% to 80% depending on the production system. The development of technologies that allow for the increase of Feed Efficiency (FE) will have direct impact on the sustainability of aquaculture industries and producers. Feed conversion rate (FCR) is a major indicator of the efficiency of a culture. It is defined as the mathematical proportion of feed given divided by an animal’s weight gain. The commercial production of cobia (Rachycemtrum canadum) has a FCR above 2.5, note that this should not be compared to other more efficient aquaculture species with FCR values close to 1. Nevertheless, improvement and optimization of FE is possible through genetic selection processes, as has been demonstrated in other species, such as trout, salmon, and tilapia.
Genetic selection of feed efficient individuals would be a very effective strategy to reduce FCR. However, the processes to evaluate and obtain individual measures of feed intake for larger sized aquaculture species is complex. Poultry and trout investigations had developed indirect strategies to enable this evaluation, correlating phenotypic and metabolic indicators such as weight lost, yield, lipid contain, among others, with the FCR. The level of these relationships allows for the identification of patterns of individual EF, and for the definition of quantitative variables to be use into a breeding program.
The aim of this study was to determine if there is a significant correlation between the different metabolic and phenotypic markers, and FCR values after recovering from fasting for cobia fish (2.0 ± 0.5 kg). If any significant correlation was found, this FCR assessment method could be integrated into the breeding program at Open Blue to improve FE. The traits used to predict FCR would depend on the magnitude of the correlations identified. This study showed that individuals with major lost weight after starvation period achieved a more efficient FCR after recovery phase. Females had a significant higher weight gain than males (+5.5%), however, significant correlation were not found between lipids contain, and FCR.