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According to a new study, by supplementing with 7% of krill phospholipids in a seabream diet, larvae exhibited enhanced growth and survival, along with significantly less lipid (or fat) deposits in the intestine and liver, as compared to fish consuming the soybean lecithin diet. The experimental diets used in the study contained increasing phospholipid contents (from 7 to 9%) derived from either krill phospholipids, provided by Aker BioMarine, or soybean lecithin.
“The researchers found that by including just 7% krill oil phospholipids in the seabream diet, the larvae exhibited enhanced growth and survival, along with significantly less lipid (or fat) deposits in the intestine and liver, as compared to fish consuming the soybean lecithin diet,” explained Andras Ziener, VP Business Development, Animal Health & Nutrition of Aker BioMarine.
The study, titled “Different phosphatidylcholine and n-3 HUFA contents in microdiets for gilthead seabream (Sparus aurata) larvae: effects on histological changes in intestine and liver”, was authored Reda Saleh, Monica Betancor, Asaad Hassan Mohamed, Tamer El-Sayed Ali and Marisol Izquierdo.
Fatty acids are being absorbed and utilized
Reda Saleh Azam, Senior Scientist at King Abdullah University of Science and Technology (KAUST), Saudi Arabia, with researchers from the Institute of Aquaculture at Stirling University, Scotland, and Universidad de Las Palmas de Gran Canaria, Spain, led this study with the goal of analyzing the effects of krill oil- and soybean lecithin-based microdiets on the intestine and liver in seabream larvae.
“The larvae received one of the five formulated test diets during the one-month experiment, after which they were evaluated for performance related to survival and growth rates.”
“The high survival rates and greater growth in the larvae fed 7% krill oil phospholipids shows that inclusion of krill in the feed ensures more of the important fatty acids are being absorbed and utilized by the fish,” assured Saleh.
“This is in line with previous research that shows that the phospholipid source is important, and krill oil phospholipids are consistently more effective in terms of health, growth and overall survival in fish,” he added.
Larval survival and growth
According to the study, the supplementation of dietary krill oil phospholipids “significantly improved” the larval survival and growth as compared to the larvae fed the soybean lecithin and control diets. Also, the overall omega-3 fatty acid composition in the body was highest in the larvae fed 7% and 9% krill oil phospholipids.
The larvae fed the soybean lecithin and control diets exhibited significantly higher presence of large vacuoles of lipid droplets in the liver and intestine, indicating poor utilization of the dietary lipids.
The inclusion of just 7% krill oil phospholipids resulted in a significant decrease in intestinal and hepatic steatosis, leading to better larval performance in terms of survival and length.
Phospholipids as energy source
Both krill oil and soybean lecithin are dietary sources of phospholipids, which is an important source of energy in fish, particularly during embryonic and early larval development. Phospholipids possess a high content of omega-3 fatty acids that are easier to absorb and digest, in addition to its feed attractant properties that support better diet quality in fish.
Previous studies have also show that phospholipids provide inositol and choline, which are important for increasing the absorption of nutrients.
The experimental diets used in the study contained increasing phospholipid contents (from seven to nine percent) derived from either krill phospholipids, provided by Aker BioMarine, or soybean lecithin. The diets were manually delivered to the fish 14 times per day over the course of one month. The larval sampling, to measure the effects of the five microdiets, was conducted on day 45 of the experiment.
