donoghue, vidal, kronfeld - 1998 - nutrition for health growth and morphometrics of green iguanas (...

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Nutrition for Health

Growth and Morphometrics of Green Iguanas (Iguana iguana) Fed FourLevels of Dietary Protein1,2

Susan Donoghue,3 Justin Vidal and David Kronfeld

Nutrition Support Services, Pembroke, VA 24136

EXPANDED ABSTRACT

KEY WORDS: iguanas dietary protein growth morphometrics

Green iguanas (Iguana iguana) are tropical, arboreal, diurnalectotherms (Iverson 1982). The lizards are herbivorous, utiliz-ing hindgut fermentation as well as hydrolytic digestion(McBee and McBee 1982); in the wild, they consume leaves,

blossoms and fruit (Allen et al. 1989). In captivity, they aretypically fed produce from groceries, including lettuce andother greens as well as fruits such as bananas. Without appro-priate supplementation, such diets are usually deficient inprotein and fiber as well as calcium and several micronutrients(Donoghue and Langenberg 1996).

A previous study examined commercial iguana diets andfound that growth was correlated with dietary fiber and protein(Donoghue 1994). The objectives of this study were to eval-uate further the dietary protein requirement and to assessmorphometric measures as indicators of growth and body con-dition in green iguanas.

Materials and methods. Animals. Yearling growing greeniguanas (n 12) were housed in 0.75 m 0.75 m 2.0 m

(l w h) vertical habitats furnished with tree branches,horizontal platforms, pools of water, full-spectrum fluorescentlights and incandescent basking lights. The room was main-tained on an 12-h light:dark cycle at temperatures of 2937Cdaytime and 2729C nighttime. Iguanas were misted dailywith water. The protocol complied with national standards forthe use and care of animals (NRC 1985).

The iguanas (8 males, 4 females) were matched by sex andsize, then assigned randomly to one of four diets. Each groupwas fed each diet in a switchback design. Accommodationperiods lasted 5 wk, and observation periods were 5 wk.

Each week the iguanas were weighed to the nearest gramand measured to the nearest mm. Measurements included body(snout-vent) length (SVL),4 total (snout-tail) length (STL),

head width, and circumferences around tail base, right thigh,mid-abdomen and mid-thorax (chest).

Diets. Diet ingredients were chopped romaine lettuce andalfalfa hay, grated apple and carrot, and premixes containing

soybean meal and micronutrients (Tables 1 and 2). Fourprotein levels [12.4, 21.8, 29.5 and 39.0% dry matter (DM)]were obtained by varying proportions of romaine, apple, carrotand soybean meal (Tables 1 and 2). Food was offered fresheach morning. At the beginning and end of the study, all dietswere analyzed by an independent forage testing laboratory(Northeast DHIA, Ithaca, NY) (Table 3). Metabolizable en-ergy (ME) values were calculated from these data, using 14.6kJ (3.5 kcal) ME/g crude protein and carbohydrate, 35.6 kJ(8.5 kcal) ME/g fat and 8.4 kJ (2.0) ME/g crude fiber (Table 3).

Data. Data were summarized as means and SEM, and ana-lyzed with the aid of a computer program (Statistix, Version4.1, Analytical Software, Tallahassee, FL). ANOVA was usedto evaluate effects of diet, iguana, and diet * iguana interac-

tion. Period was tested, found to be insignificant and deletedfrom the ANOVA. When the F-ratio was significant, meanswere compared by the least significant difference test. Linearand multiple regressions were used to test morphometric rela-tionships. Significance was inferred for P 0.05, a trend forP 0.10.

Results. All iguanas remained healthy throughout theduration of the trial, with the exception of occasional bitewounds inflicted during fights between males.

1 Presented as part of the Waltham International Symposium on Pet Nutritionand Health in the 21st Century, Orlando, FL, May 2629, 1997. Guest editors forthe symposium publication were Ivan Burger, Waltham Centre for Pet Nutrition,Leicestershire, UK and DAnn Finley, University of California, Davis.

2 Financial support was provided by Nutrition Support Service, Pembroke,VA.

3 To whom correspondence should be addressed.4 Abbreviations used: AG, abdominal girth; BW, body weight; DM, dry matter;

ME, metabolizable energy; STL, snout-tail (total) length; SVL, snout-vent (body)length; TBC, tail-base circumference; and TC, thigh circumference.

TABLE 1

Composition of four diets

Ingredient

Dietary protein, % dry matter (DM)

12 22 30 39

Romaine lettuce, g/kg 102 97 376 476Apple, g/kg 342 325 250 159Carrot, g/kg 512 487 250 159Alfalfa, g/kg 34 39 35 44Premix, g/kg1 10 52 89 162

1Details of premixes are provided in Table 2.

0022-3166/98 $3.00 1998 American Society for Nutritional Sciences. J. Nutr. 128: 2587S2589S, 1998.

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Dietary protein significantly affected growth, expressed aspercentage gain in body weight (P 0.0001; Fig. 1), chestcircumference (P 0.0051), snout-vent length (P 0.023;Fig. 1), snout-tail length (P 0.0049), head width(P 0.033), thigh circumference (P 0.010), and tail cir-cumference (P 0.012). No difference was found betweendiets containing 30 and 39% protein. Comparing 22 and 30%protein diets, the latter supported greater (P 0.05) gains inchest circumference and body weight (Fig. 1) and a trend (P 0.10) toward greater gains in head width and snout-ventlength (Fig. 1).

Body weight was related to linear measurements. Bodyweight (BW, g) was predicted best by snout-vent length (SVL,cm) and thigh circumference (TC, cm) as follows:

BW 61SVL 859 56 R2 0.923

P 0.0001 (1)

BW 17 6TC 811 54 R2 0.922

P 0.0001 (2)

Body weight was less well predicted by abdominal circumfer-ence (R2 0.898), head width (R2 0.870), chest circum-ference (R2 0.832), snout-tail length (R2 0.820) andtail-base circumference (R2 0.802), although all associationswere significant (P 0.0001).

The best-fitting multiple regression equation for the predic-tion of body weight (BW, g) used snout-vent length (SVL,cm), thigh circumference (TC, cm), abdominal girth (AG,cm), and (negatively) tail-base circumference (TBC, cm) asfollows:

BW 31.8SVL 73.0TC 25.6AG

29.0TBC 848 20 R2 0.971,

P 0.0001 (3)

TABLE 2

Composition of premixes

Dietary protein, % dry matter (DM)

Ingredient 12 22 30 39

Soybean meal, g/kg 0 787 894 936Dicalcium phosphate, g/kg 294 67 34 15Calcium carbonate, g/kg 60 24 22 20Minerals, g/kg1 415 84 39 27Vitamins, g/kg2 17 5 3 2Choline chloride, g/kg3 214 33 8 0

1 Guinea Pig Mineral Mix, ICN Biochemicals, Cleveland, OH. Mixcontains per kg: 221 g calcium carbonate, 301 g calcium phosphatedibasic, 224 g magnesium sulfate, 170 g potassium chloride, 74 gsodium chloride, 5.2 g ferric citrate, 2.4 g manganous sulfate, 1.5 g zinccarbonate, 0.59 g cupric sulfate, 0.32 g chromium potassium sulfate,0.03 g potassium iodide, 0.02 g sodium selenite.

2 Poult Pak, I. D. Russell Laboratories, Longmont, CO. Mix containsper kg: 9,900,000 IU retinyl palmitate, 4,400,000 IU cholecalciferol,11,000 mgdl--tocopherul acetate, 22 mg vitamin B-12, 110 mg biotin,8,800 mg riboflavin, 68,750 mg calcium pantothenate, 66,000 mg nia-

cin, 8800 mg menadione sodium bisulfite (source of vitamin K), 924 mgfolic acid, 4400 mg thiamin-HCl, 4400 mg pyridoxine-HCl, and 3300 mgascorbic acid.

3 ICN Biochemicals.

TABLE 3

Analyses of four diets fed to green iguanas

Dietary protein,% dry matter (DM)

SEM12 22 30 39

Protein, %DM 12.41 21.8 29.5 39.0 1.7Fat,%DM 2.6 2.0 2.6 1.9 0.5Carbohydrate,2 %DM 60.2 53.4 46.1 37.2 4.2Crude fiber, %DM 13.4 11.4 10.3 9.7 1.2Ash, %DM 11.2 11.4 11.4 12.2 0.8Energy (ME),3

kJ/g DM 12.8 12.8 13.0 12.8 0.2kcal/g DM 3.0 3.0 3.1 3.0 0.04

1 Mean of two assays.2 Carbohydrate was calculated by difference as nitrogen-free ex-

tract.3 Methods for calculating energy are presented in the text.

FIGURE 1 Growth of 12 green iguanas (mean andSEM) expressed

as percentage gain in body weight (upper panel) or snout-vent (S-V)

length (lower panel) was related to dietary protein (% dry matter).

Differences between a and b are significant (P 0.05); in the lower

panel, the difference between ab and b represents a trend (P 0.10).

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Discussion. Growth rate of yearling iguanas was depressedby lower levels of dietary protein. Our previous study of com-mercial iguana diets suggested that dietary protein and fiberaffected growth (Donoghue 1994). Observations of wild igua-nas indicated that the lizards selected plants with relativelyhigh fiber and protein, up to 33% (Allen et al 1989). In thisstudy, fiber was relatively constant, ranging from 10 to 13%DM (Table 3). The data (Fig. 1) indicate the adequacy of 30%dry matter in the form of mixed soybean, vegetable and fruitproteins.

Body weight was related to linear measurements, with SVLand TC appearing to be the best predictors. The green iguanais a cylindrically shaped animal with muscular thighs; thus itseems reasonable that measures of body length and musclemass would best predict body weight. Abdominal circumfer-ence ranked as the third best predictor of body weight. Thisassociation may reflect the influence of degree of fill in thehindgut, which is adapted for microbial fermentation (Iverson1982).

The best-fitting multiple regression equation for prediction

of body weight accounted for 97% of the variation in bodyweight. The empirical stepwise procedure selected one mea-sure of length (SVL) and three of girth (TC, AG and TBC)that would be dimensionally correct for a series of cylinders.

LITERATURE CITED

Allen, M. E., Oftedal, O. T., Baer, D. J. & Werner, D. I. (1989) Nutritional studies

with the green iguana. In: Proceedings of the Eighth Dr. Scholl Conference onNutrition in Captive Wild Animals, pp. 7381. Lincoln Park Zoological Gar-dens, Chicago, IL.

Donoghue S. (1994) Growth of juvenile green iguanas (Iguana iguana) fed fourdiets. J Nutr. 124: 2626S2629S.

Donoghue S. & Langenberg J. (1996) Nutrition. In: Reptile Medicine andSurgery, pp. 148174. W.B. Saunders, Philadelphia, PA.

Iverson, J. B. (1982) . Adaptions to herbivory in Iguanine lizards. In: Iguanas:Their Behavior, Ecology, and Conservation (Burghardt, G. M. & Rand, A. S.,eds.), pp. 6076. Noyes, Park Ridge, NJ.

McBee, R. H. & McBee, V. H. (1982) The hindgut fermentation in the greeniguana,Iguana iguana. In: Iguanas: Their Behavior, Ecology, and Conservation(Burghardt, G. M. & Rand, A. S., eds.), pp. 7783. Noyes, Park Ridge, NJ.

National Research Council (1985) Guide for the Care and Use of LaboratoryAnimals. Publication no. 8523 (rev.), National Institutes of Health, Bethesda,MD.

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