Dietary canthaxanthin reduces xanthophyll uptake and red coloration in adult red-legged partridges

Effects of Dietary Inclusion of Canthaxanthin- and α-Tocopherol-Loaded Liposomes on Growth and Muscle Pigmentation of Rainbow Trout (Oncorhynchus mykiss)

Dietary inclusion of canthaxanthin, a common carotenoid pigment, has been long practiced in aquaculture to give the favorable flesh color in farmed salmonids. However, carotenoids are associated with limited solubility and poor physicochemical stability, and their dose in fish feed is widely regulated. In this study, we included canthaxanthin- and α-tocopherol-loaded liposomes into fish diets and evaluated the effects of supplemented fish feed on fish growth, color, nutrition, and canthaxanthin deposition in fillets of cultured rainbow trout (Oncorhynchus mykiss). The liposomes were fabricated using lecithin as phospholipids with the initial concentrations (IC = mcanthaxanthin/mlipids, % wt/wt) of canthaxanthin at 0.1%, 0.5%, and 1.0%. Particle size characterization showed that liposome mean sizes were 109.70 ± 6.36, 105.10 ± 8.41, and 109.20 ± 5.66 nm (mean ± SD; n = 3), respectively, corresponding with liposomes synthesized at canthaxanthin IC = 0.1%, IC = 0.5%, and IC = 1%. The polydispersity index (PDI) of all samples remained lower than 0.2. There were no significant differences in the mean size and PDI between blank lecithin liposome and canthaxanthin- and α-tocopherol-loaded liposomes. The encapsulation efficiency of canthaxanthin- and α-tocopherol-loaded liposomes decreased when increasing the concentration of canthaxanthin in lecithin liposomes, with EE% values of IC = 0.1%, IC = 0.5%, and IC = 1% being 85.3 ± 2.1, 72.9 ± 1.8, and 55.3 ± 2.6, respectively. For fish growth, at the end of the experiment, final weight was significantly higher in fish fed with diet supplemented with 1 g/kg canthaxanthin- and α-tocopherol-loaded liposomes (IC = 0.5%) in comparison to other experimental control groups. The difference in color of the salmon muscle was most apparent after two months of feeding. However, after three months, there was no noticeable change in the color score of the fish muscle, indicating saturation of color of the fish muscle. The above results suggest the potential of canthaxanthin- and a-tocopherol-loaded liposomes as the red pigment in fish aquaculture.

Microscopic changes in the digestive organs of domestic canaries poisoned with canthaxanthin

Intoxication of canaries with canthaxanthin has been recorded more and more often since the late 1990s. This problem is related to active use of this substance for changing or increasing the colouration of this species of bird. For determining morphological changes during canthaxanthin toxicosis, we formed one control and three experimental groups of domestic canaries, which were given canthaxanthin in different doses. The material for microscopic surveys was isolated from the digestive organs of the examined birds; from this material, histological sections were prepared and stained with hematoxylin and eosin. According to the results of microscopic analysis, we determined that the intoxication of the organism of canaries with canthaxanthin causes a certain complex of changes at the tissue level. We found that canthaxanthin intoxication leads to chronic pathological processes in the digestive organs, both the digestive canal and digestive glands (pancreas, liver). In the organs of the digestive tract (glandular stomach or proventriculus, muscular stomach or gizzard, and the intestine) we found chronic catarrhal inflammation, and also proliferative processes – cellular infiltration of the stroma, overgrowth of the connective tissue. In some cases we also found distrophic processes such as keratinization of the epithelium of the mucous membrane of the glandular stomach. In the pancreas, except for edema of the stroma, no pathological processes were observed. In the liver, we found different types of dystrophy – protein (granular, hydropic) and fatty (infiltrational). With introduction of the highest doses of canthaxanthin used in the experiment, we determined a tendency towards exacerbation of pathological processes, because, apart from the already mentioned changes, we recorded manifestations of alteration (necrotic processes, disorders in blood circulation). Therefore, we proved that irrational use of canthaxanthin in canary-keeping is a factor that can negatively influence the health of these animals. Using the data we obtained, use of canthaxanthin in the diet of canaries can be correlated with their diet, thus avoiding risk of bird diseases. There is scope for further studies on the impact of canthaxanthin on other organs and the systems of the organs at microscopic level, as well as conducting biochemical and morphological analyses of blood, which would allow the creation of a new complete clinical-anatomical description of this pathology.