Effects of dietary supplementation of turmeric (Curcuma longa) extract on growth, feed and nutrient utilization, coloration, hematology, and expression of genes related immune response in goldfish (Carassius auratus)

Abstract

To examine the effect of turmeric extract (TE) on the growth, feed and nutrient utilization, coloration, hematology, and expression of immunity genes in goldfish (Carassius auratus), a 10-week feeding trial was conducted. Goldfish (7.56 ± 0.01 g/fish) were subjected to four feeding treatments using diets containing 0 (control group, TE0), 1, 2, and 3 g/kg (TE1 – TE3, respectively) of TE. Dietary TE supplementation did not significantly affect growth performance measured every two weeks (∼ 1 g/week weight gain), feed intake, or nutrient utilization but significantly increased the value of a* in the head, abdominal, and tail regions. The TE3 group had significantly higher total carotenoids in serum compared to other groups. Also, TE supplementation increased the total carotenoid content in the fin, skin, and liver with significant differences between TE0 vs. TE3 and TE2 groups. Moreover, dietary supplementation of TE increased white and red blood cells, total protein, albumin, and globulin with linear and/or quadratic effects. LDL-cholesterol and triglycerides were significantly decreased by increasing TE supplementation with the opposite tendencies in HDL-cholesterol levels. Lysozyme and IL-10 transcripts were significantly increased in the TE supplemented groups. Conversely, IL-1β transcript levels were significantly decreased in the liver by TE supplementation, and no significant differences were observed for HSP70 gene expression among all tested groups. Plasma glucose and cortisol levels were linearly decreased in all TE groups, and a quadratic effect was observed for plasma glucose levels. Taken together, the results of this study indicate that supplementing 2–3 g/kg of TE in diets could improve coloration, strengthen immunity, and alleviate stress in goldfish.