Introduction:
Aquaculture production is facing increasing sustainability challenges, particularly in sourcing feed ingredients that can support growth, health and efficient nutrient utilisation while reducing reliance on finite marine resources. There are significant concerns regarding the sustainability of the industry due to the overdependency on fishmeal and fish oil and its environmental impact . Approximately 26% of global capture fisheries by volume are reduced to fishmeal and fish oil . Lanolin is a natural wax derived from sheep wool and is composed mainly of sterols, fatty acids and wax esters . It is currently widely used in pharmaceutical and cosmetic industries due to its emollient properties and complex lipid composition . This study provides the first evidence evaluating lanolin in Pacific whiteleg shrimp (Litopenaeus vannamei) feeds.
Materials and methods:
Juvenile Pacific whiteleg shrimp (Litopenaeus vannamei) were maintained for 12 weeks and assigned to one of four dietary treatments: lanolin-coated, fish oil-coated, soy oil-coated, or uncoated feed. Growth and morphometric measurements were recorded throughout the trial, alongside external welfare assessments based on damage to the body, eyes, antennae, rostrum, and legs. At the end of the feeding period, shrimp were sampled for tissue analysis. Cholesterol concentrations were quantified in hepatopancreas and abdominal tissue to assess dietary effects on cholesterol retention and distribution. Hepatopancreas and midgut samples were collected for histological analysis; and haemolymph and midgut samples were collected for 16S rRNA sequencing (V3-V4 region).
Results:
Dietary treatment significantly influenced growth performance in Litopenaeus vannamei. Although shrimp readily consumed the lanolin-coated feed, this treatment resulted in the lowest final body weight, estimated specific growth rate (SGR), and hepatosomatic index (HSI). Apparent feed conversion ratio (aFCR) was also higher in the lanolin diet; however, this was not statistically significant. Shrimp fed the lanolin-coated diet had the lowest final mean body weight (18.21 ± 3.91g), compared with the uncoated (25.21 ± 3.85g), fish oil-coated (25.03 ± 4.06g), and soy oil-coated (23.17 ± 3.79g) treatments. In contrast, dietary treatment had no significant effect on the overall welfare index. Despite the sterol-rich composition of lanolin, cholesterol concentrations did not differ significantly among dietary treatments in either hepatopancreas or abdominal tissue. Cholesterol concentrations were significantly higher in the hepatopancreas than in abdominal tissue, consistent with its role in lipid metabolism and storage. A significant diet × tissue interaction indicated that the difference in cholesterol concentration between tissues varied among dietary treatments. Histological and microbiome analyses are ongoing.
Discussion:
Overall, lanolin did not improve growth performance in L. vannamei in its raw form. It was hypothesised that lanolin may support comparable or enhanced growth performance due to the crucial role sterols play in crustacean physiology, and their reliance on dietary sources of sterols . Previous studies have shown that dietary sterol supplementation can improve growth parameters in juvenile L. vannamei . Despite its sterol-rich composition, lanolin may not provide a readily utilisable sterol source in its raw form. Further refinement, potentially including removal or reduction of specific sterol fractions, may therefore be necessary before lanolin can be considered a suitable lipid ingredient for shrimp feeds.
Acknowledgement:
This work was funded by the Farmed animal and Aquaculture SPARK Awards (Innovate UK Business Connect).
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