Enhancing feed palatability and intakeof low fishmeal diets
by Phileoby Lesaffre
Fishmeal is considered the best source of nutrients for aquaculture feeds due to the balanced nutrient composition and the high digestibility of its ingredients. However, the continuous depletion of fish stocksrecorded worldwide,together with increased aquaculture production,is causing a shortage of fishmeal supply for the aquaculture industry.
As an immediate consequence, the price of fishmeal has spiked,which is putting the profitability of shrimp aquaculture production at risk. It is, therefore, imperative that producers identify alternative protein sources that allow for an environmentally sustainable and economically viable shrimp production.
Protein sources of vegetable origin are a valid alternative to partially replace fishmeal. Plant-based ingredients are largely available,economically advantageouswhen compared to fishmeal, and they have a good nutritional value. However, some features of vegetable materials make the transition from fishmeal to plant-based ingredients quite problematic.
Ingredients of vegetable origin often contain anti-nutritional factors (ANFs), which are biological compounds such as tannins, saponins, and glycoalkaloids that are naturally produced by plants to defeat predators in their natural environment.
These compounds have a bitter taste and, therefore, result in a reduced acceptabilityand palatability of the feed. Moreover, shrimps are able to detect the feed in the water thanks to the presence of chemical signals present in fishmeal, such as amino acids, small peptides, amines and nucleotides, that attract them.
Reducing the quantity of such key biochemical triggers through the partial substitution of fishmeal level with plant-based ingredientsin aquafeeds negatively affects attractiveness of the feed and, consequently, reduces the feed intake.
Ultimately, decreased feed palatability and feed intake have a dramatic effect on shrimp growth performance, which, in turn, severely hinder productivity and economic viability.
A biological solution to address the pitfalls of low fishmeal diets
Prosaffeed additive is a premium yeast-based product developed by Phileoby Lesaffre. It comprises a yeast fraction obtained from the primary culture of a proprietary Saccharomyces cerevisiae baker's yeast strain.
Prosaf®is producedthrough a scientifically-validated biotechnological process that autolyses the yeasts using thermal treatment and subsequently centrifuging them to separate the cell content from the cell wall. The latter component is discarded, whereas the remaining fraction is composed of a soluble cell extractwith a protein content as high as 63 percent.
The feed additive Prosaf® is also a great source of easily available amino acids.In fact, 46% percent of the amino acidspresent in this feed additive are available in their free form, while the remaining 54 percentare polymerised in smallpeptides that can be rapidly absorbed by shrimps after feeding.
It is also important to mention that Prosaf feed additive contains 7.7 percent of nucleotides, which are attractants for shrimps,and over 10 percent of glutamine, which is an amino acid known to be highly palatable.
A premium yeast fraction that boosts palatability of low fishmeal diets
A recent scientific trial carried out in Brasil was designed to investigate the beneficial effects of supplementing a low fishmeal diet with Prosaf® on feed palatability and feed intake.
Four different diets were tested: a high fishmealdiet (12% fishmeal), alow fishmeal diet (3% fishmeal), a low fishmealdiet formula withtwo percentsquid meal,and a low fishmealdiet formulawithtwo percentProsaf®.
Whiteleg shrimps (Litopenaseusvannamei) with an average 13g body weight were placed in tanks with two feeding trays in opposite sides of the tank
Multiple trials were performed in order to compare all experimental diets with the low fishmeal diet. Each trial had a duration of 15 days, shrimps were fed twice a day, and equal amounts of feed weredistributed for each meal in both feeding trays.Feed intake was calculated one hour after each meal by collecting and weighing feed left in each tray.
A significant decrease of six percent in feed intake was recorded when the amount of fishmeal in the formula was reduced from 12 percent-to-three percent , which clearly suggests that shrimpsfavoured the high fishmeal diet.
Supplementation of the low fishmeal diet with two percent squid meal showed no statistically significant effect in feed intake. However, when two percent of Prosaf feed additive was used to supplement the low fishmeal diet, feed intake significantly increased by over five percent and up to the levels recorded with the high fishmeal diet.
This result suggests Prosaf® includes highly palatable molecules that compensate for the decreased palatability of low fishmeal diets.
Prosaf® results in better feed intake for better shrimp growth
Results from this scientific trial showed that the inclusionofProsaf® (2%) is able to boost the palatability of low fishmeal diets, which is usually low. As a consequence, feed intakeincreases, thereby improvingshrimp growth performance.
The benefits of feed supplementation with this premium yeast fraction product are driven by its high content in free amino acids, including glutamate,which is known to increase palatability,as well as with small size peptides that are feed attractants for shrimp.
Prosaf®feed additive is, therefore, a valuable solution to mitigate the pitfalls associated with the challenging, yet necessary transition from high to low fishmeal diets in shrimp aquaculture.