Fillet color is a key quality trait for salmon and trout markets globally . Due to a multiplicity of factors, such as duration of growing cycles and biosecurity, challenges with fish pigmentation have been highlighted over recent years . The formulation of nature-identical astaxanthin, a liposoluble molecule, into a product form is a critical factor for stability in storage, feed application, and utilization by the fish . The digestion and absorption of dietary astaxanthin from the gut is one of the limiting factors in the pigmentation process. Prior to absorption, astaxanthin must be solubilized in the intestinal lumen. Our new research shows that the particle size of astaxanthin within formulations plays a key role in the bioavailability of astaxanthin for pigmentation.
Three test formulations containing differently sized astaxanthin particles were tested for their pigmentation efficacy in rainbow trout. Fish receiving formulations containing smaller astaxanthin particles deposited more astaxanthin than counterpart fish receiving a formulation containing a larger astaxanthin particle size. These results indicate that the size of the astaxanthin particles presented in the digestive tract drives astaxanthin solubilization and absorption by the fish digestive tract. This study highlights the importance of astaxanthin formulation properties for optimal pigmentation.