Appropriate Fat Supplementation in High‐Starch Diets Involved in the Modification of Fatty Acids Profile, Amino Acids Composition, and Antioxidant Capacity of Adult Nile Tilapia ( <i>Oreochromis niloticus</i> ) Muscle

Tilapia industry has faced great challenges due to the replacement of high-quality protein sources by a high proportion of starch. Meanwhile, the level of dietary fat is gradually reduced with the increase of oil price. High starch diets have been proved to have negative effects on flesh quality in previous studies, but the effects of fat remain unclear. The objective of the present study was to ascertain whether fat level is a requisite factor in the flesh quality of adult fish under conditions of high-starch diet feeding. The study involved adult Nile tilapia (<i>Oreochromis niloticus</i>) with an initial body weight (IBW) of 168.58 ± 2.01 g, which were fed a standard (CON) diet, a high-starch-low-fat (HSLF) diet, and a high-starch-moderate-fat (HSMF) diet for 10 weeks. The results demonstrated that the high starch diets significantly decreased the hardness, chewiness, springiness, and gumminess of muscle. HSLF diet led to a significant reduction in the weight gain rate (WGR), accompanied by an increase in crude fat content and a decrease in glycogen content in the muscle. The HSLF diet resulted in a reduction in the levels of polyunsaturated fatty acids (PUFAs), essential amino acids (EAAs), and flavor amino acids (FAAs) in the muscle tissue. Furthermore, it influenced muscle texture by reducing collagen content, fiber density, and sarcomere length. The muscle antioxidant capacity was diminished by affecting the total antioxidant capacity (T-AOC), catalase (CAT) activity, and superoxide dismutase (SOD) activity, as well as the expression levels of related genes (<i>SOD</i>, <i>CAT</i>, and nuclear factor erythroid 2 like 2 (<i>nrf2</i>)). In contrast, the HSMF diet did not have a detrimental impact on growth performance, yet it did result in a significant increase in glycogen content, hydroxyproline (Hyp), PUFAs, EAA, and FAA in muscle tissue. Moreover, the HSMF diet was observed to markedly elevate the antioxidant capacity of the muscle. It can be concluded that high-starch diet can significantly affect flesh quality by affecting the texture and muscle nutrients, as well as decreasing antioxidant capacity. Nevertheless, the inclusion of an adequate quantity of fat may prove an effective means of counteracting these unfavorable outcomes.