First feed matters
By Arne Malzahn
By Arne Malzahn
A study funded by the Norwegian Seafood Research Fund, Norway (#901561) revealed that the first feed items a larval fish eats are more important than previously thought.
In a study conducted at SINTEF Ocean and the Norwegian University of Science and Technology (NTNU) in Trondheim, Norway, researchers investigated the importance of first feed items for larval ballan wrasse. Ballan wrasse (Labrus bergylta) is an important species in Norwegian aquaculture, as it is the second most used cleaner fish species to combat salmon lice.
Common practice in larval cultivation is the use of enriched rotifers and artemia, albeit we know that these organisms does not match the nutritional demand of the larvae. In a 48-day start feeding experiment with ballan wrasse at the labs of SINTEF Ocean and NTNU (Trondheim, Norway), we studied the feasibility of replacing (Phase 1, 3 weeks) rotifers by small barnacle nauplii (Balanus crenatus) or copepod nauplii (Acartia tonsa), and (Phase 2, 3 weeks) replacing artemia by nauplii of the barnacle Semibalanus balanoides, which are larger than the B. crenatus nauplii. During phase 3 (3 weeks) all treatments received the same commercially available formulated diets.
Larvae receiving copepods as the first diet grew faster than the other groups, and had higher survival rates. Once artemia or large barnacle larvae replaced the first prey types after 3 weeks, there was no difference in growth rates between artemia and large barnacle nauplii fed larvae. Larvae also grew at the same rates after being weaned on dry diets.
An interesting observation was that the lipidomics profiles of the larvae showed a clear differentiation between the larvae according to their first diet at the end of the experiment, even though they by then received the same diets for the last 3 1/2 weeks of the experiment. Excitingly, gene expression patterns at the end of the experiment also showed very distinct differences between larvae that received enriched and natural diets as start feed. Many of the upregulated genes in the larvae started with enriched diets (rotifers) were involved in lipid metabolism, indicating that the lipids supplied with commercial enrichment products can be digested by the larvae, but additional enzymatic activity needs to be initiated by the larvae.
In conclusion, this experiment clearly shows carry-over effects from the first feed items and that these are setting the course for the later life of a fish.
Arne Malzahn is a senior researcher at SINTEF Ocean in Trondheim, Norway.