A group of researchers in Canada explored the use of either solvent extracted camelina meal (SECM) or camelina oil (CO) in the diet of Atlantic salmon parr as a replacement for fish oil.
The group published their findings in the journal Aquaculture.
“The present study was conducted to evaluate the nutritional value of camelina by-products fed to Atlantic salmon parr in terms of growth performance, carcass composition, as well as morphology and histology of the distal intestine,” said members of the research team.
They found that while small amounts of the solvent extracted camelina meal could be added to the diet, the majority of fish oil could be substituted with camelina oil. But additional research is also needed to explore anti-nutritional factors, gut immunology and the use of camelina by-products.
“CO can be utilized by fish as efficiently as fish oil, and contains unknown factors which can improve hindgut health,” they said. “We recommended 50% CO, 100% CO, and 5% SECM in Atlantic salmon parr diet based on the results of this study.”
Why camelina oil or meal?
Multiple studies have been done exploring the use of plant proteins including soybean meal, corn gluten meal and canola meal as alternatives to the finite and price volatile fish oil and fishmeal.
“Applied research conducted in the past two decades has established the maximum amounts of some plant protein and lipid sources that carnivorous fish can tolerate anti-nutritional factors (ANFs) or toxicants,” they said. But some improvements have been made, they added.
Camelina sativa, an oilseed cultivated in Europe and North America, is high in alpha-linolenic acid, which has previously been used to replace fish oil.
“High oil residue camelina meal (HOCM), the remaining meal after conventional oil, is removed from camelina seed by mechanical pressing using an expeller,” the researchers said. “HOCM contains 33.9% crude protein and 12% crude lipid (NRC, 2011).”
The remaining crude protein level can be improved to 39.3-47.4% if the by-product is processed with a solvent extraction, they said. But SECM also has several ANFs, including glucosinolates, phytic acid, tannins, sinapine, mucilage, and non-starch polysaccharides.
In rainbow trout, the product was found to limit thyroid function, they said, but did not limit growth when used at 16-20% inclusion.
The product has not been explored for use in Atlantic salmon diets, nor is it known if it will produce enteritis the way soybean meal can, the researchers said. “Soybean-induced enteritis causes decreased height of mucosal folds/villi, disappearance of supranuclear vacuoles (SNV) in the intestinal epithelium, widening of lamina propria (LP) in the center of mucosal folds, infiltration of inflammatory cells in the lamina propria (Baeverfjord and Krogdahl, 1996), increased number of goblet cells (GC), and thicker sub-epithelial mucosa (SM) (Uran et al., 2008b),” they added.
Seven experimental feed combinations were tested, said the researchers. The diets included a control made from fish meal and fish oil; four diets with SECM at 5%, 10%, 15% and 20% and two diets where either 50% or 100% of the fish oil was substituted with camelina oil (CO).
The SECM diets included fish oil, they said.
About 1,050 fish were used in the 16-week trial, said the researchers. Fish batch weight per tank and feed consumption were noted every four weeks.
One fish per tank was harvested at the start of the trial, they said. Six fish per tank were collected at weeks 8 and 16 for body and distal intestine analysis, also at the end, weight, fork length, live weight of the six fish were measured.
Weight gain (WG), daily growth coefficient (DGC), feed consumption (FC), the feed conversion ratio (FCR), condition factor (CF), protein retention ratio and hepato-somatic index (HIS) were determined, they said.
Fish ate similar amounts of all the diets, but the consumption of the 100% CO replacement diet was higher than that of the SECM diets for weeks 13-16, said the researchers. Weight gain for fish getting the 15% SECM diet was lower than the control for weeks 13-16, but the same was not true for fish getting the 20% SECM diet.
“Final weight was not reduced by SECM or CO diets, but fish fed the CO diets had higher final weight compared to the fish fed the 10, 15 and 20 SECM diets,” they said. “Feed conversion ratio was unaffected by dietary treatments.”
Daily growth coefficients for the CO groups also outperformed fish getting the SECM diets, said the researchers. SEMC fish did not match the control group growth, but the 20% group was similar.
Hepato-somatic index, protein retention and fish carcass elements were not altered by diet, they said. Glucosinolate intake grew as SECM rose from 5 to 20%.
Most intestinal factors were not altered by the diet, and there was no sign of severe inflammation, said researchers. “The lamina propria of control fish was significantly narrower than those fed the 15% and 20% SECM diets, but was significantly wider than fish fed the 50% CO diet,” they added.
Title: The effects of camelina oil and solvent extracted camelina meal on the growth, carcass composition and hindgut histology of Atlantic salmon (Salmo salar) parr in freshwater
Authors: Chang Lin Ye, Derek M. Anderson, Santosh P. Lall