Skretting Marine Hatchery Diet Goes Green

“Gemma Wean already found favour in hatcheries; now information from Skretting Aquaculture Research Centre (ARC) and refinements in our production equipment have given us the opportunity to improve it further,” says Eamonn O’Brien, Product Manager for Skretting Marine Hatchery Feeds. “We enhanced the nutritional balance, for example by adding carefully selected marine micro algae, which is why it is green.

Marine larvae in the wild eat a wide range of marine organisms including marine algae, either directly or via species they predate on that also consume the algae. Skretting aimed to mimic this natural diet. Adding sources of marine algae delivers a positive probiotic effect that is good for health and efficient digestion in the larvae: the algal component stimulates digestive enzymes. The blend of essential oils and immuno-stimulants that proved successful in the original Gemma Wean is retained. However, based on information from Skretting ARC, the protein content was raised from 60 to 62 per cent and the lipids reduced from 15 to 14 per cent. These are highly concentrated marine oils with a high DHA to EPA ratio and phospholipid content.

Mr O'Brian said: “Ingredient changes, with a new balance of phospholipid classes, and advances in refinement technology provide a free flowing feed that disperses readily on the surface of the water. We ran pre-commercial trials in France, Italy, Spain and Turkey with sea bass, sea bream, meagre and turbot. All hatcheries gave positive feedback, commenting that these characteristics mean the feed behaves well in automatic feeders. They also reported that it is easier to maintain good water quality, that the feed is readily accepted, that larval growth is excellent and they are all impressed with the natural green colour!”

Gemma Wean is cold extruded at Skretting’s specialist plant in Vervins, France; the low temperature production process retains the nutritional value of the ingredients. Recently installed micro-cutting equipment improved micro-pellet consistency and minimised dust. “We extended the size range,” adds Mr O’Brien. “Originally it ran from 0.1mm to 0.3mm and now there is a Gemma Wean Diamond 0.5mm pellet, to cover the early post-weaning stage to where the pre-grower diets begin. Although fry at this stage have a very high growth potential, hatcheries often switch to low cost diets with less protein and higher fat levels. That can be a false economy. By extending the Gemma Wean size range we are enabling hatcheries to provide the fry with the nutrition they need to achieve their growth potential.”

In parallel, Skretting revised the Gemma pre-grower diets that follow on from Gemma Wean. “We offered two options, Gemma PG and Gemma Diamond,” says Mr O’Brien. “The majority of customers opted for the extra benefits of Gemma Diamond, so we are concentrating on that range, reducing the number of products from 11 to five. These run from micro pellets of 0.8mm up to 1.8mm. Gemma Diamond has the higher protein and lower fat levels that Skretting ARC reports will deliver the best growth, fish quality and condition factor index.”