Comparison of the Retention Rates of Synthetic and Natural Astaxanthin in Feeds and Their Effects on Pigmentation, Growth, and Health in Rainbow Trout (Oncorhynchus mykiss)

Abstract

The coloring efficiency and physiological function of astaxanthin in fish vary with its regions. The aim of this study was to compare the retention rates of dietary astaxanthin from different sources and its effects on growth, pigmentation, and physiological function in Oncorhynchus mykiss. Fish were fed astaxanthin-supplemented diets (LP: 0.1% Lucantin^® Pink CWD; CP: 0.1% Carophyll^® Pink; EP: 0.1% Essention^® Pink; PR: 1% Phaffia rhodozyma; HP: 1% Haematococcus pluvialis), or a diet without astaxanthin supplementation, for 56 days. Dietary astaxanthin enhanced pigmentation as well as the growth of the fish. The intestinal morphology of fish was improved, and the crude protein content of dorsal muscle significantly increased in fish fed with astaxanthin. Moreover, astaxanthin led to a decrease in total cholesterol levels and alanine aminotransferase and aspartate aminotransferase activity in plasma. Fish fed on the CP diet also produced the highest level of umami amino acids (aspartic acid and glutamic acid). Regarding antioxidant capacity, astaxanthin increased Nrf2/HO-1 signaling and antioxidant enzyme activity. Innate immune responses, including lysozyme and complement systems, were also stimulated by astaxanthin. Lucantin^® Pink CWD had the highest stability in feed and achieved the best pigmentation, Essention^® Pink performed best in growth promotion and Carophyll^® Pink resulted in the best flesh quality. H. pluvialis was the astaxanthin source for achieving the best antioxidant properties and immunity of O. mykiss.

Keywords: antioxidant status; astaxanthin; coloring; flesh quality; immunity; trout.

Figure 1

Comparison of pigmentation in the dorsal muscle of Oncorhynchus mykiss fed on an experimental diet for 56 days ((A) Visual color inspection; (B) Salmon color fan value). The color value of fresh fillet in Oncorhynchus mykiss fed on experimental diets. Values are presented as mean ± SE, n = 12. Different letters represent statistical differences (p < 0.05).

Figure 2

Long-chain fatty acid levels in the abdominal muscle of Oncorhynchus mykiss fed with the experimental diets for 56 days. Values are presented as mean ± SE, n = 4. The superscript letters indicate a significant difference at p < 0.05.

Figure 3

The intestinal histology of Oncorhynchus mykiss was fed with experimental diets for 56 days. Magnification 200×.

Figure 4

Effects of different diet treatments on the intestinal morphometry of Oncorhynchus mykiss. Values are presented as mean ± SE, n = 12. The superscript letters indicated significant differences at p < 0.05.

Figure 5

Effects of different diet treatments on the plasma parameters of Oncorhynchus mykiss. Values are presented as mean ± SE, n = 12. The superscript letters indicated significant differences at p < 0.05.

Figure 6

Effects of different diet treatments on antioxidant parameters in Oncorhynchus mykiss. Values are presented as mean ± SE, n = 12. The superscript letters indicate significant differences at p < 0.05.

Figure 7

Effects of different diet treatments on the expression of antioxidant-related genes in the liver of Oncorhynchus mykiss. Values are presented as mean ± SE, n = 12. The superscript letters indicated significant differences at p < 0.05.

Figure 8

Effects of different diet treatments on the expression of immune-related genes in the liver of Oncorhynchus mykiss. Values are presented as mean ± SE, n = 12. The superscript letters indicated significant differences at p < 0.05.