Color development and growth performance of Xiphophorus hellerii fed with experimental feeds incorporated with Tagetes erecta petal meal and whole meal of Euphausia sp

Abstract

The color intensity of ornamental fishes contributes greatly in determining the value, marketability and demand of the fish. Growth enhancement of fish, leading to reduction of the duration of culture period, could reduce production cost. Therefore, color manipulation and growth enhancement have become priorities of ornamental fish farmers. The use of suitable ingredients in feed formulation and feeding the fish have displayed the potential to achieve those goals ethically and effectively. Therefore, during the present study two experimental feeds were prepared by incorporating Tagetes erecta (marigold) petal meal (Treatment 01) and whole meal of Euphausia sp. (krill; Treatment 02) to the same ingredients used to prepare the control feed. Three groups of Xiphophorus hellerii (Swordtail fish) were maintained separately under equal conditions, except feeding with 03 different feeds, over 84 days. At the end of the experimental period, color intensity was measured using the red value scale in ImageJ software, where a lowest red value indicates strongest color intensity. The fish fed with Marigold feed exhibited the significantly lowest (p < 0.05) red value (117.37 ± 2.35), indicating the deepest intensity of red color and the highest red value (159.32 ± 2.92) was recorded for the control group (having the lowest color intensity. The highest percentage weight gain was recorded for the fish in Treatment 02 (78.90 ± 0.01%) followed by Treatment 01 (56.49 ± 0.01%) and the lowest weight gain (52.22 ± 0.04%) was observed in control treatment (p < 0.05). Significantly (p < 0.05) highest specific growth rate (SGR) (1.85±0.05%) was observed in treatment 02 followed by treatment 01 (0.99±0.01%) while the control treatment had the lowest (0.88 ± 0.06) SGR value. Percentage ash content in marigold petal incorporated feed was significantly higher (16.67 ± 0.31; p < 0.05) than those of control and krill meal based feed (both feeds had the same value; 13.33 ± 0.40). The food conversion ratio of treatment 01 (1.96 ± 0.08) was higher than those of treatment 02 (1.44 ± 0.21) and the control treatment (1.76 ± 0.10). Marigold petal incorporated feed had contributed to a more pronounced development of red color confirming that it could be used for red color enhancement in Swordtail fish. Krill meal had demonstrated that growth promotion in Swordtail fish could be achieved by incorporating krill meal into the feed.