Imagine a delicious Lamington cake, drizzled in chocolate syrup and covered in coconut flakes.
The same principles that make lamington cake irresistible apply to fish feed. The cake itself equates to the fundamental building block in fish feed (i.e. basal feed: amino acids, lipids and carbohydrates). The coconut flakes are the equivalent to feed additives. Though present in micro quantities, feed additives play a key role in improving health, growth and water quality, in return is essential in boosting production output. Without them, feed loses its essence, just like a lamington cake without its coconut flakes, basic and unappealing.
Similar to some humans, some fish are picky eaters and may have exquisite taste for certain ingredients. Like sprinkles atop a delicious sundae, feed additives improve palatability and digestibility of feed.
Different Types of Feed Additives
Feed ingredients is a mixture of both organic and inorganic compounds. There are 3 type of feed additives:
Essential additives enhance nutritional value in feed, without them, fish may undergo deficiency diseases. Essential additives includes:
Growth promoting non-essential additives
Auxiliary additives
Feed colorants for example carotenoid pigments in crustaceans and fish gives cultured species the similar coloration as their wild counterparts.
Binders ensures water stability of fish feed, present at around 2-8% of feed for higher stability of pellets. Commonly used binders include agar-agar, carboxymethylcellulose (CMC), bentonite, guar gum, lignin sulfate, polyvinyl alcohol, sodium alginate and wheat gluten
Molasses is a co-product of the sugar industry. It is a thick and sticky syrup with a high nutritional value: it contains on average 50% of sugar content and minerals such as iron, calcium, magnesium and potassium.
For recommended nutrient specifications for fish and shrimp, please refer to this source.
How do feed producers know how much additives to add in?
Different aquaculture species have different feed requirements. There has been extensive research and testing done to obtain the optimal feed combination for different species at different life stages to maximize growth and mitigate disease.
For example -
A team of international researchers assessed the impacts of dietary vitamin D3 on growth performance, calcium absorption, mineralization, and skeletal anomalies during the development of gilthead seabream larvae until 47 days post-hatching.
Gilthead seabream larvae showing different types of skeletal deformities. (a) Normal and completely mineralized larvae, (b) Kyphosis (c) neurocranium anomaly, (d) scoliosis
Feed Production Challenges
There are three key issues within the aquaculture feed industry, namely:
Strong fluctuations of feed ingredient prices in combination with low market prices for farmed products makes optimizing cost-efficiency of feed essential.
Formulating fish meal and fish oil with alternative ingredients for carnivorous fish and shrimp has proven to be difficult without adverse impacts to health or growth.
A wide range of viral, bacterial and parasitic diseases continues to wreck havoc to fisheries and hatcheries.
These challenges require multi-disciplinary solutions from genetics to farm optimization, and are drawing more attention to functional additives.
The Rise of Functional Feed Additives
What are functional feed additives?
Powered by natural, bio-active compounds with specific functional properties, functional feed additives enhance digestive and metabolic processes to improve the effectiveness of novel feed formulation. A wider selection of natural compounds with gut modulating capability have also been identified and incorporated for disease prevention.
Examples include:
botanical extracts and phytobiotic compounds - plant derivatives with diverse range of properties including antioxidant, antimicrobial, anticarcinogenic, analgesic, insecticidal, antiparasitic, anticoccidial, growth promoter’s appetite enhancement, stimulant of secretion of bile and digestive enzyme activity
mycotoxin binders - secondary metabolites produced from different species of the fungi are called mycotoxins. Binders (e.g. aluminium silicates, bentonite, montmorillonite, hydrated sodium calcium alumina silicates, Zeolitic materials) are commonly used at 1-10g/kg in feed to counter the negative impact of aflatoxin (mycotoxin) to prevent kidney and liver failure.
organic acids - weak carboxylic short-chain fatty acids and partially dissolves in water to form a hydrogen ion (H+) and a carboxylate ion (-COO-). Organic acids decreases pH in stomach and intestine and improves digestion.
enzymes - commonly used enzymes in aquaculture feeds are phytase, carbohydrase, protease, lipase, alpha - amylase, papain, pepsin to improve digestion and growth
yeast - contains a high amount of enzymes, fatty acids, amino acids, vitamin B. Saccharomyces cerevisiae is commonly used in aquaculture. Yeasts has immune-stimulatory properties and enhances anti-oxidization in finfish and crustaceans.
probiotics and prebiotics (mentioned above)
Applications of Functional Feed Additives
Example 1 - improving feed cost-efficiency (problem) by adding digestive/metabolic enhancers (solution)
Nutriad’s functional feed additive research focuses on compounds that are heat-stable to simulate practical processing conditions on farms. Digestive aids have shown improved nutrient utilization from cheap ingredients in omnivorous fish (e.g. tilapia and catfish), when applied in scale, this will reduce operation cost. Further field evaluations are required to determine digestive aids’ interactions with feed quality and optimal dosage at different life stages of fish.
Sampaio-Gonçalves et al. (2012) evaluated the effect of the dosage and feed quality on the efficacy of a digestibility enhancer for tilapia during a production cycle in cages in Brazil. The best results obtained by supplementing the control feed throughout the production cycle with 3 kg/MT of the feed additive, resulting in improved survival (+2.8%), daily weight gain (+5%), feed conversion (-6.4%), fileting yield (+1.5%), visceral fat deposition (-9.9%), hepatosomatic index (-22%), and viscerosomatic index (-10.7%). The optimal additive treatment improved farm revenues with 17% compared to the unsupplemented control group with a return on investment (ROI) of 3.8:1.
Example 2 - tackling early mortality syndrome in shrimp (problem) using feed additives with multiple mode of actions (solution)
Compounds active in Quorum Sensing (QS) disruption are increasingly investigated as potential alternatives to antibiotics due their efficacy at low concentrations and the low chances on bacteria developing resistance against these non-lethal molecules. Quorum Sensing (QS) is a form of bacterial communication, based on the production and secretion of signaling molecules which can be detected by adjacent bacteria. Blocking bacterial communication (called quorum sensing inhibition or also quorum quenching) is a novel way of preventing them to trigger pathogenicity.
