## 2 New Trends in Aquaculture Feed Production
### Recent and Future Trends of the Sector  
The life cycle of rainbow trout begins with brood stock breeding and egg fertilization and continues through the growing phase. Achieving high-quality standards at the first stage (selection of breeding stock and egg production) of the cycle is critical to the entire production process. Recently, in the rainbow trout sector, there has been evidence of a high degree of vertical integration among farms [1]. In particular, several production farms have integrated their activities with brood stock breeding and egg production activities. Female reproductive characteristics (egg diameter, fecundity rate, and number of viable eggs) vary with rearing conditions (temperature, feeding, light cycle, etc.) and genetic selection. Egg quality characteristics vary according to the number of eggs laid and the ability to develop a viable embryo [1]. Recently, automated phenotyping systems, using image analysis technologies (and wireless data transfer), have been developed to determine the presence of dead eggs and/or any embryonic malformations [3]. At the first stage of the production chain, water reuse methods (Recirculating Aquaculture Systems, RASs) allow the farmer a greater degree of control (over production), to reduce water consumption and the release of effluent into the environment. Due to high costs and high energy use, RASs are used only at certain stages of the cycle (particularly in hatcheries where control over environmental conditions is more critical and unit values higher).  
\begin{table}
\begin{tabular}{c c c c} \hline \hline
**Protein Ingredient** & **Inclusion Level (\%)** & **Effects** & **Reference** \\ \hline Mixed plant meals & 46, 70, 100 & FBW (reduction) & [56] \\ _Salisachytrium linacinum_ & 5 & FBW (no difference) & [57] \\ _Hermetia illucens_ & 10, 20, 30 & FBW, SGR, FCR (no difference) & [58] \\ _Tenchito molitor_ & 50 & FBW (no difference) & [59] \\ _Sacammos cerevisiae_ & 10, 20, 30 & FBW, FCR (no difference) & [60] \\ _wickenhammos anomalus_ & 10, 20, 30 & FBW, FCR (no difference) & [60] \\ \hline \hline \end{tabular}
\end{table}
Table 9: Effects of alternative diets on growth and quality parameters in rainbow trout.  
In the following growing phase, feed conversion ratio (FCR) is the most important parameter for improving the production indices and reducing the environmental impact [42]. Reducing FCR by 10% also results in a 9.5% reduction in the carbon footprint [34]. Recently, several companies have used underwater cameras and sonars to reduce feed waste. The feed industry is continuously working on developing new feed ingredients and improving formulations with higher energy content. While in the 1990s fishmeal and fish oil made up more than 80% of trout feeds, today, conventional marine-derived ingredients make up only 25-30%. As a result, in farmed trout, the content of long-chain omega-3 fatty acids has decreased. Genetic selection and marker-assisted selection have also been used to improve fish growth and health [25]. For example, selected trout show 10-15% weight gain per generation with feeds based on plant ingredients. In addition, supplementing feed with nutraceuticals, prebiotics and probiotics, and plant extracts is used to improve fish growth and immunity and reduce the use of antibiotics. In recent years, researchers have conducted extensive studies to develop new vaccines to control diseases caused by bacteria or viruses. To date, two effective vaccines for IPNV (Infectious Pancreatic Necrosis Virus) and ERM (Enteric Red Mouth) are used in rainbow trout farming.