| In this experiment,feed with 0 and 150 mg/kg astaxanthin was used,the effects of astaxanthin on the growth and body color of Paramisgurnus dabryanus were studied by means of microscopic observation and molecular biological methods,so as to lay a theoretical foundation and provide a reference for astaxanthin as a colorant in practical production.A total of 600 two kinds of body color Paramisgurnus dabryanuswith(11.25±0.16)g were randomly divided into 4 groups with 3repetitions per group and 50 fish in each repetition.Fish in the four groups were fed diets containing 0 and 150 mg/kg astaxanthin for 60 d,respectively.Samples were taken every 10 d for a total of 7 times.The results showed that: 1.Effect of astaxanthin on the growth of Paramisgurnus dabryanus with two body colorsAdding 150 mg/kg of astaxanthin into the feed can effectively promote the growth of common body color and golden yellow body color of Paramisgurnus dabryanus.However,the interaction between body color and astaxanthin had no significant effect on the final body weight(FBW),weight gain(WG)and specific growth rate(SGR)of Paramisgurnus dabryanus(P>0.05).The FBW of the two kinds of body color Paramisgurnus dabryanus increased from 0 to 60 days.And the sampling results showed that when the level of astaxanthinin was 150 mg/kg,the FBW of two kinds of body color Paramisgurnus dabryanus was significantly higher than that of 0 mg/kg group(P < 0.05).There was no significant difference in the FBW between two kinds of body color Paramisgurnus dabryanus(P>0.05).The WG of Paramisgurnus dabryanus with two body colors decreased from 0 to 60 days.When astaxanthin level was 150 mg/kg,the WG of the two kinds of body color Paramisgurnus dabryanus was significantly higher than that of astaxanthin 0 mg/kg group(P<0.05).There was no significant difference in the WG between the two sikn colors of fish.The SGR of the two kinds of Paramisgurnus dabryanus decreased from 0 to 60 days.When astaxanthin level was 150 mg/kg,the SGR of the two kinds of body color Paramisgurnus dabryanus was significantly higher than that of astaxanthin 0 mg/kg group(P<0.05).There was no significant difference in the SGR between the two sikn colors of fish.2.Effect of astaxanthin on pigment cells in skin of Paramisgurnus dabryanusAccording to the microscopic observation results showed,the dominant pigment cell of common body color Paramisgurnus dabryanus is melanocyte,the dominant pigment cells of golden yellow body color Paramisgurnus dabryanus are xanthophore and allophore.In 0-60 days,when the astaxanthin level was 150 mg/kg,the number of melanocytes decreased gradually and was more dispersed,and it was lower than 0 mg/kg astaxanthin group.However,the number of xanthophore and allophore increased gradually and were more densely distributed,it was higher than astaxanthin 0 mg/kg group.3.The effect of astaxanthin on the pigment content in the skin of Paramisgurnus dabryanus with two body colorsAdding 150 mg/kg astaxanthin to the diet that can effectively regulate the skin color of common body color and golden yellow body color Paramisgurnus dabryanus.At 0 and 10 days,the interaction between body color and astaxanthin level had no significant effect on the carotenoid content in the skin tissue of common body color and golden yellow body color of Paramisgurnus dabryanus,but it had significant effect on carotenoid content at 20,30,40,50 and 60 days(P<0.05).In 0-60 days,when the level of astaxanthin was 0 mg/kg,the carotenoid content of common body color Paramisgurnus dabryanus with the skin tissues that presented a trend of increased first and then decreased,while the carotenoid content of golden yellow body color Paramisgurnus dabryanus with the skin tissues presented a trend of gradual decrease first and then gradual.When the level of astaxanthin was 150 mg/kg,the carotenoid content of common body color and golden yellow body color Paramisgurnus dabryanus with the skin tissues that presented a trend of increased first and then gradually.There was a significant difference for the carotenoid content in the skin tissues of the two body colors of Paramisgurnus dabryanus,and the carotenoid content in the group with astaxanthin 150mg/kg was significantly higher than that 0mg/kg group with the two body colors of Paramisgurnus dabryanus(P<0.05).Adding 150 mg/kg astaxanthin to the diet,the melanin content was lower than that of the 0 mg/kg group in the skin tissues of two body colors of Paramisgurnus dabryanus.And at the 0 and 60 d,the interaction between body color and astaxanthin level had no significant effect on the melanin content in the skin tissues of Paramisgurnus dabryanus,but there were significant effect for the melanin content on 10,20,30,40 and 50 days(P<0.05).In 0-60 days,when the level of astaxanthin was 0 mg/kg,the melanin content of common body color Paramisgurnus dabryanus with the skin tissues that presented a trend of increased first and then decreased,while the melanin content of golden yellow body color Paramisgurnus dabryanus with the skin tissues presented a trend of decreasing.When the level of astaxanthin was 150 mg/kg,the melanin content of common body color Paramisgurnus dabryanus with the skin tissues that presented a trend of gentle first and then decreasing,while the melanin content of golden yellow body color Paramisgurnus dabryanus with the skin tissues that presented a trend of decreasing first and then gentle.There was a significant difference for the melanin content in the skin tissues of the two body colors of Paramisgurnus dabryanus,the melanin content in the group with astaxanthin 150mg/kg was significantly lower than that 0mg/kg group of the two body colors of Paramisgurnus dabryanus(P<0.05).4.Effects of astaxanthin on the m RNA expression levels of Sox10,Agouti,Mc1 r,Mitf,Tyr,Tyrp1 and Tyrp2 in the skin and muscle tissues of the two body colors of Paramisgurnus dabryanus.The results showed that Sox10,Agouti,Mc1 r,Mitf,Tyr,Tyrp1 and Tyrp2 genes were all expressed in the skin and muscle tissues of the two body colors of Paramisgurnus dabryanus.When adding 0 mg/kg astaxanthin,the Sox10,Agouti,Mitf,Tyr,Tyrp1 and Tyrp2 m RNA expression levels were significantly different between the common body color and golden yellow body color Paramisgurnus dabryanus(P < 0.05),but the Mc1 r m RNA expression level was not significant difference between the two kinds of body colors Paramisgurnus dabryanus.When adding 150 mg/kg astaxanthin,the Sox10,Agouti,Mitf,Tyr,Tyrp1 and Tyrp2 m RNA expression levels were significantly different between the common body color and golden yellow body color Paramisgurnus dabryanus(P < 0.05),but the Mc1 r m RNA expression level was not significant difference between the two kinds of body colors Paramisgurnus dabryanus.The m RNA expression levels of Sox10,Agouti,Mitf,Tyr,Tyrp1 and Tyrp2 in the 150 mg/kg astaxanthin group were significantly different from those the 0 mg/kg in the skin and muscle tissues of the two body colors of Paramisgurnus dabryanus(P < 0.05),but the Mc1 r m RNA expression level was not significantly different.According to the above results,The addition of astaxanthin 150 mg/kg to the diet of paraloach can improve its final body weight,average weight gain rate and specific growth rate,It can also increase the content of carotenoids in the skin of fish,Melanin content decreased,In addition,it can regulate the m RNA expression of Sox10,Agouti,Mc1 r,Mitf,Tyr,Tyrp1 and Tyrp2 in fish skin and muscle,but has no effect on the expression of MC1 R gene. |
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