Abstract

Chemical analysis is an integral part of a good quality control program to ensure the nutritional value of feedstuffs. Establishing a quality control program may begin with identifying feeds to be analyzed based on their overall impact with the animal collection and instituting a regular schedule for sampling feeds for chemical analysis. The types of analyses to be performed are selected based on the type of feed to be analyzed and any nutritionally related problems. Specific protocols should be developed and followed for obtaining representative samples. A number of factors must be considered when choosing a laboratory to perform the specified analyses. Proper implementation of a quality control program, using chemical analysis as a tool, will produce results essential to maintaining high standards of nutritional care for captive zoo animals.

Purpose of Quality Control

If it looks good and the animals eat it, it must be okay, right? This may sound nonsensical, but all too often this type of criteria is applied when determining the quality of feeds and food items used in zoo animal diets. While the appearance and palatability of a feed or food item are important, the chemical analysis more accurately determines the value of these items to captive animals. In addition to chemical analysis, use of feed microscopy may be, on occasion, appropriate to evaluate feed quality.

Feeds should be systematically and regularly analyzed for a number of reasons. Manufactured feeds may not meet specifications due to inattention to detail during mixing or due to mechanical problems during the manufacturing process. While feeds may meet minimum nutrient level specifications, some nutrients may be included at higher inappropriate levels. Another reason for conducting routine feed analyses is to determine if unauthorized ingredient substitutions have been made. Often this is best accomplished by microscopic analysis. It is crucial to analyze foods such a frozen fish, to monitor the wide fluctuations in some nutrients (e.g., fat) which may occur on a seasonal, regional or species-specific basis. Fluctuations in nutrient composition also occur in forages based on season, region produced and species of plant, and in whole prey items such as rodents and insects due to variation in developmental stage or differences in the diet fed to prey items.

Development and implementation of a quality control program is essential to ensure the nutritional quality of feeds and food items used in captive animal diets. Chemical analysis is an integral part of such a program. A schedule for sampling and analysis should be established for all feeds, especially those that represent a significant part of the zoo’s budget and those used in large quantities.

Identifying Feeds for Analysis

One of the first steps in instituting a quality control program is to identify primary feeds; that is feeds that are used in large quantity and fed to a number of different animals throughout the collection. For most zoos, these would include forages, fish, herbivore pellets, dog food and primate diets. Since the quality of the primary feeds will have a greater impact on a larger proportion of the collection, these feeds should be analyzed more often than the specialty feeds. Primary feeds should be analyzed at least four times per year. Specialty feeds, those that are fed to a small proportion of the collection, should be analyzed at least twice per year. If problems are encountered, they can be analyzed more frequently.

In general, it is not economically feasible or necessary to set up a regular schedule of sampling and chemical analysis for produce items (e.g., fresh fruits and vegetables), since produce inventory typically has a rapid turnover, usually 1 wk or less. In addition, produce items should contribute minimally to an individual animal diet, with the majority of nutrients supplied by a nutritionally complete feed. Therefore, the produce portion should not significantly impact the overall nutrient composition of the diet and slight variations in produce nutrient content are of less concern.

Choosing the Types of Analyses Performed

The analyses performed depend on the type of feed item and the reasons for sampling the item. Typically, chemical analysis of feeds should include proximate analysis (dry matter, crude protein, ether extract, and ash), gross energy, and fiber fractions (neutral detergent fiber, acid detergent fiber, and acid lignin). Analysis for major minerals (calcium, phosphorus, sodium, potassium and magnesium) as well as trace minerals (iron, copper, manganese, selenium, and zinc) is also important. For some feeds, it may be important to analyze for various vitamins, but cost may be a consideration. Analyzing for other specific nutrients may be necessary if there is evidence of a specific health problem with a possible nutritional link. Routine analyses which should be performed, based on type of feed, are listed below in order of priority:

• Forages—proximate analysis, fiber fractions, gross energy, major and trace minerals.
• Dry/semi-moist/moist feeds—proximate analysis, gross energy, fiber fractions, major and trace minerals.
• Fish—proximate analysis, gross energy, fat soluble vitamins, major and trace minerals.
• Meats—proximate analysis, gross energy, major and trace minerals, vitamins A and E.
• Whole prey—proximate analysis, gross energy, major and trace minerals, vitamins A and E.

Selecting the Representative Sample

The goal when sampling feeds for analysis is to obtain a small portion that is representative of the entire lot (batch, catch, load, etc.) of a particular feed or food item. Obtaining a representative sample is critical because it is frequently the initial sampling step that introduces the greatest variability and most affects the reliability of the analysis results. Ideally, every new lot should be sampled and sent for analysis. Also, the larger the sample size, the more reliable the results. However, the constraints of time, cost, and facilities available for collecting samples and analyzing data usually do not allow for the ideal situation. It is important to establish a plan for sampling and chemical analysis to improve the reliability of results.

Protocol for Sampling Forages for Nutritional Analysis

Hay should be sampled using a core forage sampler.

1.  A composite of cores from 15–20 bales should be collected from each lot, of each hay type to be sampled.

2.  The cores should be taken by drilling into the center of the end of the bale.

3.  The complete length of the sampler should be drilled into the bale of hay.

4.  The sample should be placed in a plastic bag, sealed and labeled with the type of hay, the date the sample was taken, and the name of the zoo.

5.  The samples should be stored in a cool, dry place.

Protocol for Sampling Dry/Semi-Moist/Moist Feeds for Nutritional Analysis

Dry/semi-moist/moist feed samples should consist of at least 500 g.

1.  Samples should be taken from at least 10 containers (bags, boxes, cans) of feed. Samples consisting of at least 100 g should be collected from the center of each container and combined.

2.  A 500 g sample should be held for analysis and the remainder discarded.

3.  The sample should be placed in a plastic bag, sealed and labeled with the type of feed, manufacturer’s name, date code or lot number, the date the sample was taken, and the name of the zoo.

4.  Dry feed samples should be stored in a cool, dry place. Samples of semi-moist/moist feeds should be placed immediately into freezer storage.

5.  All opened dry/semi-moist feed containers, which do not require refrigeration, or freezing after opening must be closed and sealed. Open containers of semi-moist/moist feeds, which require refrigeration or freezing, should be used immediately or discarded.

6.  For dry feeds delivered in bulk and placed in hoppers, random sampling of feeds should take place on days when the hopper is being filled.

Protocol for Sampling Fish and Other Frozen Feeds for Nutritional Analysis

Fish

1.  Frozen fish samples should consist of at least 1 kg for each species.

2.  For IQF fish, samples should be taken from at least five, randomly selected cases, for each species of fish.

3.  Bulk frozen fish should be sampled by cutting sections from blocks using a band saw. Samples should be taken from each of five randomly selected cases of fish. Cases should be opened and the block of fish cut into two approximately equal sections. One of the two sections should have a strip (approximately 5 cm wide) cut from the original outer side and from the inner, newly cut side. Total sample size obtained should be at least 3 kg from the five cases, this should be thoroughly mixed, a 1-kg sample held for analysis and the remainder discarded.

4.  Sampled fish should be placed immediately into large, thick plastic bags that have been prelabeled with species of fish, lot number and date of catch, the date the sample was taken, and the name of the zoo. The bags should be placed immediately into freezer storage.

Other Frozen Feeds

1.  Other frozen feeds, such as tubes of carnivore diets, should be sampled by cutting approximately ¼ kg off the end of each of 5, randomly selected tubes, using a band saw.

2.  Sampled feeds should be placed immediately into large, thick plastic bags that have been prelabeled with type of feed, manufacturer’s name, date code or lot number, the date the sample was taken, and the name of the zoo.

Protocol for Sampling Whole Prey for Nutritional Analysis

Vertebrate Prey

1.  Frozen or fresh vertebrate prey samples should consist of a minimum of 10 animals, not to exceed 1 kg total weight for each species.

2.  Sampled prey should be placed into large, thick plastic bags that have been prelabeled with species, the date of shipment, the date the sample was taken, and the name of the zoo. The bags should be placed immediately into freezer storage.

Invertebrate Prey

1.  Frozen or fresh invertebrate prey samples should consist of a minimum of 100 g for each species; protocol for sampling marine invertebrates is the same as fish.

2.  Sampled prey should be placed into large, thick plastic bags that have been prelabeled with species, the date of shipment, the date the sample was taken, and the name of the zoo. The bags should be placed immediately into freezer storage.

Choosing a Laboratory

Once appropriate samples have been collected and are ready for chemical analysis, there are numerous laboratories from which to choose, including commercial, university and hospital laboratories. There are even a few zoos with nutrition laboratories. However, all laboratories are not equal in their abilities or experience in analyzing different types of feeds and food items. For example, a lab specializing in hay analysis may not be familiar with procedures for sample preparation and analysis of fish or whole prey items. Cost is certainly a consideration when choosing a laboratory for performing analyses. It is important to note that inexpensive analyses are no bargain if the results produced are not reliable. Therefore, prospective laboratories should be critically evaluated before sending samples for analysis. Questions to ask include:

1.  Does the laboratory have experience performing the type of analysis requested on the specific type of feed to be analyzed?

2.  Do they use AOAC (Association of Official Analytical Chemists) approved methods or methods which are proven/accepted and referenced in current literature?

3.  Are they willing to provide detailed references on the methods used?

4.  Are they familiar with differences in method of sample preparation depending on the type of food sample being analyzed?

5.  Do they regularly check the accuracy of results by running duplicate samples and/or do they participate in the National Institute of Laboratory Standards and have their own quality control programs?

Professionals in the nutrition field may be a resource to be consulted for recommendations on laboratories and accepted analytic methods. For more specific information on analytic and sampling techniques the following literature may also be referenced:

1.  AOAC. 1997. Chapter 4: Animal feed. In: Official Methods of Analysis. Volume I, 16th ed., 3rd revision. Association of Official Analytical Chemists International, Gaithersburg, MD, Pp. 4-1.

2.  Christen, G.L. 1994. Sampling and sample preparation. In: Introduction to the Chemical Analysis of Foods. Nielsen, S.S. (ed.), Jones and Bartlett Publishers, Inc., Boston, MA, Pp. 39–50.

3.  Nielsen, S.S. 1994. Introduction to food analysis. In: Introduction to the Chemical Analysis of Foods. Nielsen, S.S. (ed.), Jones and Bartlett Publishers, Inc., Boston, MA, Pp. 3–10.

4.  Pomeranz, Y. and C.E. Meloan. 1994. Sampling. In: Food Analysis Theory and Practice. 3rd ed. Chapman and Hall, New York, NY, Pp. 16–25.