Food Preparation
Safe food‐handling procedures should be implemented for animal diets. These include washing hands before putting on gloves to handle food; washing gloves, knives, cutting boards, and other utensils between food types to prevent cross‐contamination; and using properly cleaned and sanitized utensils and food containers (Henry et al. 2010). Cleaning (removal of visible food and debris) and sanitizing (reducing the number of micro‐organisms on cleaned surfaces to safe levels) are separate, sequential processes. Cleaning can be done with soap and warm water. The recommended method for sanitization is a high‐heat dishwasher (>71°C (160°F)). Chemical sanitization is an acceptable alternative and can include one of the following methods (Henry et al. 2010):
100 mg/L chlorine for >20 seconds.
25 mg/L iodine solution for >60 seconds.
200 mg/L quaternary ammonium compound for >60 seconds.
0.5% Virkon‐Aquatic® for 10 minutes.
After the sanitizing step, dishes should be rinsed. Chlorine may be deactivated using sodium thiosulfate. Dishes should be allowed to air‐dry and not towel‐dried.
Seafood
Given the perishable nature of seafood, food‐handling is crucial. Thawing should always be done in air under refrigeration at <4°C (39°F), never at room temperature. If rapid thawing is required, food items may be thawed in a sealed and closed container under cold running water. Incorrect thawing may result in nutrient losses, fat rancidity, microbial buildup, and loss of palatability (Crissey 1998; Henry et al. 2010).
Food should be inspected during preparation. Fresh and fresh‐thawed fish should have bright red gills, clear corneas (often with lens opacities), and firm elastic flesh with no breaks in the skin. Old or thawed and refrozen fish are dull in appearance, have opaque corneas, red‐bordered eyes, and soft flesh that leaves finger impressions and tears readily; these should not be fed (Crissey 1998; Henry et al. 2010).
All thawed seafood should be kept iced or refrigerated until feeding and should be used within 24 hours. Thawed food should never be refrozen. Periodic nutrient testing for quality control (see below) is encouraged, especially for fish that are high in fat.
Produce
Handling of vegetables, fruit, and forage should minimize bacterial contamination, especially in areas where other food items are prepared. Vegetables and produce should be washed and inspected for signs of spoilage, pests, and environmental damage. Individual standards should be developed for each produce or vegetable type (Henry et al. 2010).
Pelleted and Flake Feeds
Dry feeds should be inspected for foreign material, dust, mold, evidence of pests, color, smell, and product uniformity.
Gel Foods
Gel diets are generally prepared on site by mixing a dry meal base with hot water. It is critical to follow manufacturers' directions regarding ratios of dry product:water, water temperature, and mixing time to ensure proper hydration of any gelling agents and to ensure food safety (e.g. heat inactivation of micro‐organisms). If a facility is using an in‐house recipe, data on heat inactivation of common micro‐organisms may be of use (e.g. Ericsson et al. 2002). If medications or other supplements are added to gel foods, it is important to consider the temperature to which the compound can be exposed while maintaining activity. For example, it may be preferable to inject a medication into a single piece of cooled gel food, rather than adding a medication to hot gel food during the preparation process. Once prepared, gel diets should be stored and handled as raw foods.
Quality Control
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.
Nutritional Support
Changes in feeding frequency or amount may be indicative of a problem such as inappropriate feeding, inappropriate environmental conditions, or disease (see Section B). Action should be taken to rule out or resolve any environmental stressors and to identify any disease issues.
Feeding can be encouraged by using food that is of the highest quality, appropriate for the species, of a size that can be processed by the individuals, and fed at appropriate times of day. This is easily confirmed if other members of the species are readily consuming the diet. Changing the feed items or delivery method may encourage feeding. This can include changing from pole feeding to toss feeding and/or changing where in the system or water column food is offered. If social stressors are a factor (e.g. tank‐mate displacement), isolating individuals for directed feedings can be helpful.
Appetite Stimulants
Fish primarily detect food through olfaction and sight; however, appearance, feel, and taste are key factors in determining whether food will be consumed (Lall and Tibbetts 2009). Compounds present in the diet may act as feeding‐stimulants