Читать книгу Clinical Guide to Fish Medicine - Группа авторов - Страница 169

Diet analyses are an important part of monitoring the composition of food items offered to animals (Bernard and Allen 2002; Henry et al. 2010). Seafood, such as frozen or fresh fish, should be analyzed to monitor the wide fluctuations in nutrients that can occur on a seasonal, regional, or species‐specific basis. Dry feeds should be analyzed due to potential inconsistencies in manufacturing. A schedule for sampling and analysis should be established, especially for items that represent a significant part of the diet. Wherever possible, primary food items, especially seafood, should be analyzed once per year or ideally with each batch. Specialty feeds that are fed to a small proportion of the collection may be analyzed less frequently. If problems are encountered, analyses may be conducted more frequently.

The types of analyses performed depend on the type of food item and the reasons for sampling. Most analyses should include proximate composition:

 Moisture (or dry matter).

 Crude protein, fat by ether extract, and ash.

 Fiber (neutral detergent fiber [NDF], acid detergent fiber [ADF], and acid lignin), particularly for plant‐based or commercially prepared food items. Seafood is generally low in fiber, so this analysis is less important.

Other useful analyses include:

 Gross energy, which may be useful in understanding total calories and energy available to the animal.

 Macrominerals (Ca, P, Na, K, Mg).

 Trace and ultra‐trace minerals (Cu, Co, Fe, I, Mn, Se, Zn).

 Vitamins (vitamin A, B1 [thiamine], C, D3, E as α‐tocopherol, β‐carotene).

Food items may also be tested for microbiological loads, toxins, organic contaminants, or pesticide residues.

When sampling feeds for analysis, the goal is to obtain a small portion that is homogeneous and representative of the entire lot (e.g. batch or harvest). Food items should be submitted to the laboratory in the form that they are prepared and consumed by the animal (e.g. fillet versus whole fish, shell removed, and supplements added). The reader is referred to Bernard and Dempsey (1999) for greater details on obtaining a representative sample and selecting an appropriate laboratory. Once the nutritional analyses are received, the results should be compared to pre‐established criteria, previous analyses, “typical” nutrient composition of common food items, and the information presented in Tables A4.5–A4.8 (Dierenfeld et al. 1991; Bernard and Allen 2002; Henry et al. 2010). Consultation with a nutritionist is recommended to help identify deviations in nutrient composition.