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Last updated January 1, 2014

Chemical Analysis of Six Commercial Adult Iguana, Iguana iguana, Diet

Charles A. Hurty (1), Duarte E. Diaz MS (2), Jennifer L. Campbell MS (2), Greg A. Lewbart MS, VMS, DACZM (1)

Abstract
Reptile keeping is one of the most rapidly expanding areas in the pet industry. In response to this trend, several pet food companies have formulated specialized diets and supplements that cater to the unique nutritional needs of different reptile species. Since nutrition is a key variable of captive reptile husbandry, we investigated the nutrient composition of six commercially available adult iguana, Iguana iguana, feeds that are intended for use as principle diets. We compared the results of our analyses to the nutrient information provided on packaging labels and to available information on the suggested nutrient recommendations for iguanas. Crude protein contents ranged from 13.2 1% dry matter (DM) to 27.15% DM with two of the six diets containing a lower protein than indicated on the label. Crude fat content ranged from 1.46 ± 0.44% DM to 10.25 ± 0.05% DM with three of the six diets having fat contents below the amount stated on labels. The acid detergent fiber (ADF) content, a measure of insoluble fiber, ranged from 5.42 ± 0.54% DM to 13,95 ± 0.27% DM. Great variety in concentrations of iron (Fe), copper (Cu), calcium (Ca), phosphorus (P), zinc (Zn), magnesium (Mg), and manganese (Mn) was demonstrated.

KEY Words: green iguana, Iguana iguana, nutrition, diet, reptile, husbandry, feeds

 Introduction
With the recent release of various dinosaur-theme movies, such as Disney's Dinosaur and Speilberg's Jurassic Park, many individuals have become curious and enamored with reptiles (Allen and Oftedal, 2001). As a result, the number of reptilian pets has swelled, establishing reptile keeping as a rapidly growing segment of the pet industry. However, even with a history of more than four thousand years of keeping reptiles in captivity, the provision of good husbandry continues to consistently challenge reptile enthusiasts (Frye, 1973). Supplying an appropriate environment and offering complete and balanced nutrition are arduous tasks that often result in frustration for pet owners (Cooper, 1990, Campbell, 1991, Baer, 1994, Donoghue. 1995, 1996, Allen and Oftedal, 2001). Often the loss of the exotic reptilian pet can be traced to nutritional problems. In some cases completely inappropriate diets are offered; for example, a carnivorous species is fed a diet suited for a herbivore, resulting in nutritional disorders due to long term maintenance on a diet that is lacking in one or more vital nutrients (Allen and Oftedal, 2001).

Concomitant with the expanding popularity of reptile keeping, pet food companies have sought to meet the growing demands of reptilian pet owners. Designer reptile diets claiming to offer balanced, complete nutrition have been introduced to the market. It may he premature for these companies to make such claims since standardized nutrient requirements that would define a complete and balanced diet have neither been established nor recognized (Donoghue, 1995, 1998). Without the scrutiny of a regulatory agency to monitor feed composition and advertising claims, some of the diets being produced and marketed for the reptile pet may not be nutritionally complete (Donoghue, 1995, 1998. 1999, Donoghue and Langenberg, 1996). While formulated diets can greatly benefit owners and their pets by providing necessary nutrients to an intended species, they may also threaten the health status of the animal if certain nutrients are not included or are present in improper amounts (Lawton, 1996, Allen and Oftedal, 2001). During our initial investigation of iguana products, we identified more than 25 diets labeled specifically for adult iguanas.

We selected six adult iguana diets from pet stores in the Raleigh, North Carolina area, analyzed their contents, and compared our data to the product labels and to various suggested nutrient recommendations for iguanas. Our primary concern is the investigation of quality control of various diets marketed for adult iguanas. We are neither making an attempt to outline suggestions for formulating diets, nor making judgments about the nutritional soundness of these diets.

Materials and Methods
Samples were finely ground through a Wiley Mill (Arthur H. Thomas, Philadelphia, PA) using a 2mm screen. Duplicate samples were weighed, freeze-dried, and percent moisture was calculated. The samples were then incinerated in a muffle furnace at 550°C (1020°F) overnight and total ash was measured. Crude fat (CF) was determined by extraction with petroleum ether. Samples were analyzed for dry matter (DM) (AOAC, 1990), neutral detergent fiber (NDF) and acid detergent fiber (ADF) (Van Soest 1967, modified by Ankom Technologies, Fair Park, NY) and crude protein (CP) (AOAC, 1990). Calcium, phosphorous, potassium, magnesium, zinc, iron, manganese and copper minerals were analyzed using an inductively coupled plasma (ICP) optical emission spectrometry (Perkin-Elmer, Norwalk, CT) by the method described in Boss and Fredeen (1997). Gross energy was analyzed by adiabatic bomb calorimetry (IKA® Works, Inc. Model c5000, Wilmington, NC) (McLean and Tobin, 1987).

Results
The six diets demonstrated much variety in chemical composition (Table 1). The Kaytee, Zoo Med, and Tetra/Terrafauna diets were found to contain only 46%, 37%, and 49% of the minimum fat level stated on their guaranteed analysis, respectively. The Fluker Farms diet and the Kaytee diet contained less protein than the minimum protein levels indicated on their product labels (13.3% DM and 14.0% DM, respectively). The other four feeds exceeded the guaranteed minimum crude protein level stated on the label. All six diets contained an amount of moisture consistent with packaging label values. The three diets (Zoo Med, Tetra/Terrafauna, and Fluker Farms) that listed ash amounts had ash levels that agreed with the product label amount

Table 1. Dry matter nutrient composition of dry formulation commercial adult green iguana diets. Endorsement of the diets by the authors should not be implied.

The mineral concentrations of the six dry commercial adult iguana diets are presented in Table 2. Only one company (Fluker Farms) listed information concerning mineral content of the iguana diet. Copper content of the Fluker Farms diet was consistent with the packaging label. The information in Table 2 will be considered in the discussion.

a. KT Adult iguana, Fortified Daily Diet, Kaytee Products, Inc., Chilton, WI 53014.

b. All Natural Adult Iguana Food, Zoo Med Laboratories. Inc., San Luis Obispo, CA 93401.

c. Reed's Iguana Food, Tetra/Terrafauna, TetraSales USA, Blacksburg, VA 24060.

d. Adult Iguana Food, Maintenance Formula, RepCal Research Labs, Los Gatos, CA 95031.

e. Fluker's Fruit Formula Iguana Diet, Fluker Farms/Laboratories, Port Allen, LA 70767.

f. T-Rex Iguana Dry Formula, Adult Fruit & Flower Formula, T-Rex Products, Inc., Chula Vista, CA 91911.

g. Recommendations from Allen and Oftedal. 2001.

h-i. Recommendations from Donoghue and Langenberg, 1996

N/A = no available recommendation.

These recommendations should not necessarily be utilized to formulate diets, but do provide references for comparison. These ranges include recommendations for growing green iguanas.

Discussion
Nutrient analysis of the six iguana diets indicated that most of the diets contained levels of nutrients similar to or in excess of guaranteed minimal values. Analysis also revealed that large differences exist between the studied diets (Table 2). It has yet to be determined if such considerable differences between these feeds are biologically significant. For example, 98 ppm zinc in an adult iguana diet may have the same biological and physiological significance as a diet with 170 PPM zinc. However, further information is needed to determine if 759 PPM of iron is either toxic or interferes with other mineral metabolism when fed for long periods because levels between 750 to 1250 PPM can be considered potentially harmful iron concentrations for ruminants and poultry (Underwood and Suttle, 1999).

The Zoo Med feed contained 27.15% .DM crude protein, which is a level of dietary protein that is recommended for growing, juvenile iguanas. Such a diet may be inappropriate for adult iguanas, which do not require such high levels of protein. More may not necessarily be better.

Table 2. Since the calcium-phosphorus ratio (Ca:P) has been linked to the development of metabolic bone disease in iguanas, it is one of the nutritional parameters that has been repeatedly investigated and explored (Scott, 1992, Burgmann, et al, 1993, Donoghue, 1995. 1998, Frye, 1995). Recommended Ca:P ratios range from 1:1 to 3:1 (Frye, 1995, Donoghue and Langenberg, 1996, Donoghue, 1999a, Allen and Oftedal, 2001).

Table 3 offers the Ca:P ratios of the six dry iguana diets that were analyzed. It is also important to consider the actual amounts (% DM) of calcium and phosphorus in the diet. While the ratio may fall within suggested guidelines present in the literature, amounts actually present in the diet may fall short of the published recommendations (see Table 2).

Conclusion
The goal of this project was to evaluate quality control and nutritional claims of six commercial diets. The extraordinary degree of product diversity should be noted. While many companies market their product as a complete and balanced diet for pet iguanas, it is important for veterinarians and pet owners to be aware that nutritional requirements have not yet been defined for adult iguanas. More research is required, and until such investigation takes place, we must realize that the diets formulated for adult iguanas may or may not be nutritionally complete. The importance of performing laboratory analyses of the accuracy of feed tags and of the appropriateness and quality of adult iguana diets cannot be stressed enough.

Further investigation of the more than 25 adult iguana diets should include an analysis of vitamin content. Since reports of failure to thrive among captive iguanas are frequently attributed to hypovitaminoses and hypervitaminoses, it would be prudent to determine the vitamin levels present in adult iguana foods (Cooper, 1990, Scott, 1992, Burgmann, et al, 1993, Baer, 1994, Donoghue and Dzanis, 1995, Frye. 1995, Lawton, 1996, Donoghue, 1998, 1999a). Furthermore, actual feeding trials designed to determine the nutrient requirements of iguanas are required before completeness and balance of reptile diets can be determined.

References

Allen ME, Oftedal OT. 2001. The nutritional management of a herbivorous reptile, the green iguana (Iguana iguana), in Jacobson ER (ed.): Biology, Husbandry, and Medicine of the Green Iguana. Krieger Pub Co, Malabar, FL, in press.

Association of Official Analytical Chemist. 1990. Official Methods of Analysis. 5th edition, AOAC, Washington DC.

Baer DJ. 1994. The nutrition of herbivorous reptiles. In Murphy JB, Adler K, Collins JT (eds): Captive Management and Conservation of Amphibians and Reptiles. SSAR, Ithaca, NY: 83-90.

Boss BB, Fredeen KJ. 1997. Concepts, instrumentation, and techniques in inductively coupled plasma optical emission spectrometry. The Perkin-Elmer Corporation. Norwalk, CT.

Burgmann PM, McFarlen J, Thiesenhausen K. 1993. Causes of hypocalcemia and metabolic bone disease in Iguana iguana, JSEAM, 2:63-68.

Campbell TW. 1991. Husbandry concerns for pet reptiles. Vet Tech, 12(9):664-666.

Cooper JE. 1990. Feeding exotic and pocket pets. J Sm Anim Prac, 31(10):482-488.

Donoghue S. 1995. Growth of juvenile green iguanas (Iguana iguana) fed four diets. J Nutrition, 124:2626S-2629S.

Donoghue 5. 1998. Nutrition of pet amphibians and reptiles. Sem Avian Exot Pet Med. 7(3):148-153.

Donoghue S, Dzanis D. 1995. Evaluating commercial diets. Proc ARAV, 74-78.

Donoghue S, Langenberg J. 1996. Nutrition. In Mader DR (ed): Reptile Medicine amid Surgery. WB Saunders Co, Philadelphia, PA: 148-174.

You don't need to be a vet to join the Association of Reptilian and Amphibian Veterinarians, nor need to be a member to attend their annual conferences or buy a copy of their conference proceedings. For more information, please visit their website at www.arav.org.

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