Dietary supplementation of Aurantiochytrium sp. significantly improved growth, feed utilization, skin lightness, muscle protein synthesis capacity, and whole-body protein in juvenile African sharptooth catfish (Clarias gariepinus)

Cultivated Aurantiochytrium sp. FIKU018 contained 64.0% crude lipid, 22.6% crude protein, and 4.47% crude ash, on a dry matter basis. This ingredient has been supplemented in artificial diets across a number of aquatic animal species. However, no studies have evaluated this dietary supplement for African sharptooth catfish (Clarias gariepinus) aquaculture. In this study, isonitrogenous, isolipidic, and isoenergetic diets were formulated containing different grade levels of dried Aurantiochytrium sp. (0, 2, 4, 6, 8, and 10%). These diets were given to triplicate groups of juvenile African sharptooth catfish (1.68–1.70 g body weight) for six weeks. At the end of the feeding trial, fish in all treatments had similar survival rates, ranging from 88.9% to 97.2% (P > 0.05). The growth performance (weight gain = 68.5 g) and feed utilization (feed conversion ratio = 1.47 g feed g gain−1, protein efficiency ratio = 1.94 g gain g protein−1) indicated a suitable level of 6% dried Aurantiochytrium sp. in diet. Based on broken-line analysis indicated an optimal supplementation level of 6.41% would produce the highest weight gain. This preferred treatment significantly improved skin lightness, muscle protein synthesis capacity, and whole-body crude protein (P < 0.05) without causing effects on fillet color parameters, digestive enzyme activities, and myosin and actin in white muscle (P > 0.05). Our observations suggest that 6.41% is the optimal dietary supplementation level of Aurantiochytrium sp. for juvenile African catfish. The supplemented diet that produced the best results can be used in the cultivation of African sharptooth catfish, and could support the use of dried Aurantiochytrium meal as an alternative feed supplement for other aquatic animals.