Читать книгу Clinical Guide to Fish Medicine - Группа авторов - Страница 150

There is some evidence that fish can select for certain nutrients when given dietary choices, particularly for macronutrients such as protein (da Silva et al. 2016). When fish could self‐select between protein (from casein and gelatin), lipid (from fish oil/soybean oil mix), and carbohydrate (from dextrin), selection varied by wild‐type feeding strategy. More carnivorous species selected for higher protein intake of 55–62% protein, 16–23% carbohydrate, and 16–22% lipid (Sánchez‐Vázquez et al. 1999; Rubio et al. 2003; Almaida‐Pagán et al. 2006). More omnivorous species selected lower protein intake levels: Nile tilapia ~45% protein, 32% carbohydrate, and ~22% lipid; and goldfish ~22% protein, 45% carbohydrate, and ~32% lipid (Sánchez‐Vázquez et al. 1998; Fortes‐Silva et al. 2011). Selection of lipid sources has also been demonstrated: tilapia selected flaxseed or fish oil‐based diets (sources of omega‐3 fatty acids) in preference to soybean oil‐based diets (omega‐6 fatty acids) (Fortes‐Silva et al. 2010). There is less evidence of selection for appropriate nutrient intake of vitamins or minerals in fish. An important caveat is that low quality food items may not allow for selection to occur, because of an inability to modify intake levels to meet nutrient needs (e.g. low‐protein diet), a net loss of nutrients (e.g. increased synthesis of microbial protein resulting in a net protein loss), and/or ingestion of toxins that may limit intake. An excellent discussion of these factors and the dietary choices of the herbivorous butterfish (Odax pullus) is presented by Baker et al. (2016).