Tissue-Specific Cadmium Accumulation, Metallothionein Induction, and Tissue Zinc and Copper Levels During Chronic Sublethal Cadmium Exposure in Juvenile Rainbow Trout

Insects are emerging as a sustainable alternative to fishmeal and fish oil in aquafeeds. This study assessed the effect of graded incorporation levels of defatted yellow mealworm (Tenebrio molitor) protein meal on juvenile rainbow trout (Oncorhynchus mykiss) growth performance, body composition, and apparent nutrient digestibility. The trial comprised five dietary treatments: control diet with 25% fishmeal, and four experimental diets with yellow mealworm protein meal at 5%, 7.5%, 15%, or 25%, which corresponded to a fishmeal replacement of 20%, 30%, 60%, or 100%, respectively. After 90 days, the graded incorporation of insect protein meal led to a significant stepwise increase in final body weight, and a significant improvement of specific growth rate, feed conversion ratio, and protein efficiency ratio compared to the control treatment. Regardless of the incorporation level, the insect protein meal had no effects on fish whole-body composition and apparent digestibility coefficients of dry matter, protein, fat, phosphorus, and energy. Protein, phosphorus, and energy retention significantly increased in fish fed the diets with an insect protein meal. In conclusion, the yellow mealworm protein meal could effectively replace 100% of fishmeal in the diet of juvenile rainbow trout with positive effects on its overall zootechnical performance.

Download Full-text

Sublethal effects of terbium and praseodymium in juvenile rainbow trout

The Science of The Total Environment ◽

10.1016/j.scitotenv.2021.146042 ◽

2021 ◽

pp. 146042

Author(s):

Houda Hanana ◽

Zofia E. Taranu ◽

Patrice Turcotte ◽

Christian Gagnon ◽

Joanna Kowalczyk ◽

...

Keyword(s):

Rainbow Trout ◽

Sublethal Effects ◽

Juvenile Rainbow Trout

Download Full-text

Video surveillance methods to evaluate individual feeding response in rainbow trout (Oncorhynchus mykiss, Walbaum)—implications for feeding regime optimisation

Aquaculture International ◽

10.1007/s10499-021-00671-z ◽

2021 ◽

Author(s):

Philip Niclas Just ◽

Bernd Köllner ◽

Matthew James Slater

Keyword(s):

Rainbow Trout ◽

Oncorhynchus Mykiss ◽

Video Surveillance ◽

Average Weight ◽

Short Term ◽

Feeding Regime ◽

Daily Feeding ◽

Juvenile Rainbow Trout ◽

Feeding Regimes ◽

The Impact

AbstractPrecisely analysing and optimising feeding regimes is central to salmonid growth performance and delivery of special diets. The current study developed novel video surveillance methods and analysis techniques to assess individual feed intake and minimum pellet intake (MPI) in individually identified juvenile rainbow trout, Oncorhynchus mykiss. Three trials were conducted to test the impact of short-term starvation (N=112 [16 tanks, 7 fish per tank], average weight=27.1±3.4g, age= 119 days), portion numbers per feeding (N=105 [15 tanks, 7 fish per tank], average weight=22.8±2.1g, age= 99 days) and varied numbers of daily feeding events (N=84 [12 tanks, 7 fish per tank], average weight=32.4±3.3g, age= 133 days). All trails were carried out in a recirculating aquaculture system with 20 tanks held at 15 ± 0.5°C. All individuals were code-tagged and high quality video images were taken and analysed to identify all feeding interactions. Individual trout feeding activity under different feeding regimes could be precisely analysed with the video methods developed. Moving from one to two daily feeding events doubled pellet intake per fish from 27.4 ± 5.8 to 52.8 ± 11.5 pellets. Pellet intake (58.8 ± 24.2 pellets) did not increase at three daily feeding events but became more variable across fish. MPI nearly doubled to 30 pellets in fish receiving two daily feeding events (MPI30: chi-squared = 8.74, df = 2, p = 0.01). Short-term starvation had no influence on intake (28 ± 8 pellets/fish) or MPI. Increasing portion number from one (27.8 ± 7.4 pellets fish−1) to two (31.1 ± 7.4 pellets fish−1) or more did not significantly increase the number of ingested pellets. Adjusting the feeding regime by increasing daily feeding events to two, possibly combined with multiple portions, can increase pellet intake and reduce the heteroscedasticity of pellet intake. The methods presented in this study are viable for analysing feeding regimes for juvenile rainbow trout and controlled feedstock/supplement delivery. Implications for analyses with other species and for vaccination optimisation are discussed.

Download Full-text