Available via license: CC BY-NC-ND 4.0
Content may be subject to copyright.
Received: 23 September 2020
Accepted for publication: 20 June 2022
Slov Vet Res 2022; 59 (3): 137–47
DOI 10.26873/SVR-1216-2022
UDC 591.53:616-008.71: 598.121/.128
Original Research Article
Introduction
Chelonians are commonly kept pets.
Overweight, accelerated growth rate and
metabolic bone disease of nutritional origin are
common as a result of inadequate nutrition and
housing (1, 2, 3, 4, 5). The natural diet of aquatic
chelonians consists of several animal species,
and seasonality is strong in the case of tortoises
(6, 7, 8, 9, 10, 11, 12, 13). Captive chelonians
should be fed a natural diet to achieve a growth
rate similar to that of free-ranging animals (2,
3, 7, 15). The energy expenditure of reptiles is
only 25–35% that of mammals (16). Feeding
frequency and quantity must also be mentioned,
EVALUATION OF COMMERCIAL TORTOISE AND TURTLE FEEDS
Nikoletta Hetényi*, Emese Andrásofszky
Department of Animal Nutrition and Clinical Dietetics, Institute for Animal Breeding, Nutrition and Laboratory Animal Science, University of
Veterinary Medicine, 1078, István u. 2, Budapest, Hungary
*Corresponding author, E-mail: hetenyi.nikoletta@univet.hu
Abstract: Captive chelonians should be fed a natural diet to achieve a growth rate similar to that of free-ranging animals. A wide
range of commercially formulated foods dedicated to chelonians is available. Feeding commercial foods has the advantage of
convenience. On the other hand, species-specific information on the nutritional requirements of chelonians is not available yet.
The aim of this study was to analyse and evaluate commercial pellets and feeds for chelonians. Commercial pellets (ntortoise = 7,
nturtle = 7, from 6 companies) dedicated to carnivorous aquatic tur tles and herbivorous terrestrial tortoises, and other aquatic tur-
tle feeds (lyophilised beef heart, dried aquatic inver tebrates, and whole frozen fish) were bought in pet shops. Whole frozen fish
served as a reference feed for carnivorous aquatic turtles. The chemical composition as well as calcium (Ca) and phosphorus
(P) contents were determined. Single-sam ple t-test was used with the label information as null hypothesis and the results of own
parallel analyses for crude protein (CP), ether extract (EE), crude fibre (CF), Ca and P. The labelling of some of the pellets was defi-
cient as nutritive values, Ca or P data were missing (tortoise pellets: 4 out of 7; turtle pellets: 5 out of 7). The label data differed sig-
nificantly (p<0.05) from the results of our own analysis for 13 out of the 14 pellets. None of the tor toise pellets met the requirements
of the animals completely. Because of the inadequate Ca:P ratio only one turtle pellet could be accepted. Accordingly, none of the
commercial pellets can be recommended as main or only feed.
Key words: nutrition; pellet; metabolic bone disease; chelonian
as periodic starvation is common in the natural
habitat of chelonians.
A wide range of commercially formulated
foods dedicated to chelonians is available.
Feeding commercial foods has the advantage of
convenience. On the other hand, species-specic
information on the nutritional requirements of
chelonians is not available yet. Because of this,
the composition of commercial pellets is not
necessarily adequate for the target species. The
formulation of pellets varies from manufacturer
to manufacturer (14, 17). Controlled animal
trials evaluating the effects of such feeds are also
missing.
The aim of this study was to analyse and
evaluate commercial pellets and feeds for che-
lonians.
138138 N. Hetényi, E. Andrásofszky
Material and methods
Commercial pellets (n=14, from 6 companies,
tortoise: A = Nutrin-Aquarium Tortoise Sticks;
B1 = Sera Raffy Vital Herbivor; B2 = Sera Reptil
Herbivor, C1= JBL Herbil; C2 = JBL Agivert; D =
Exo Terra European Tortoise Adult; E1 = Tetra
Tortoise; turtle: C3 = JBL Agil; C4 = JBL Tortil;
JBL = Rugil; E2 = Tetra ReptoMin Sticks; E3 =
Tetra ReptoMin Energy; E4 = Tetra ReptoMin
Baby, F = Panzi) dedicated to carnivorous aquatic
turtles and herbivorous terrestrial tortoises,
and other aquatic turtle feeds including whole
frozen sh (European smelt; Osmerus eperlanus)
and dried aquatic invertebrates (Baltic prawn
[Palaemon adspersus] and dried freshwater crab
[Gammarus roeseli]) were bought in pet shops.
The whole frozen sh served as a reference feed
for carnivorous aquatic turtles.
The chemical composition as well as calcium
(Ca) and phosphorus (P) content of the pellets,
lyophilised beef heart, dried aquatic invertebrates
and whole frozen sh were determined according
to the AOAC (16) prescriptions (10 analyses/pellet
for nutrients and 2 analyses/pellet for Ca and P).
All statistical tests were conducted using R
3.5.1 software (R Development Core Team, 2009,
Vienna, Austria). Single-sample t-test was used
with the label information as null hypothesis and
the results of own parallel analyses for crude
protein (CP), ether extract (EE), crude bre (CF),
Ca and P. The level of signicance was p < 0.05.
Results
The nutrient content of tortoise and turtle
pellets is shown in Tables 1 and 2. In the case of
tortoise pellets our own data differed signicantly
(p<0.05) from the label information on several
occasions. The CP contents were signicantly
higher (A, B2, D and E1) or lower (B1 and C2) than
those indicated on the label. This can be explained
by the ingredients of animal origin (sh and sh
derivatives, molluscs and shellsh) in 3 products
(B1, D and E1) and the presence of alfalfa meal
(A) or algae (B2). Compared to the declared value,
CF was signicantly higher in 4 pellets (A, C1, C2
and E1) and lower in 3 pellets (B1, B2 and D). The
EE was signicantly lower in 4 and higher in 3
pellets than the data on the label. The crude ash
(CA) content was also signicantly lower than the
declared value, with the exception of two samples
(A and C2). The nitrogen-free extracts (NFE) varied
between 48.2–71.2% and the two cereal grain free
pellets (C1 and E) had the lowest carbohydrate
content).
The Ca and P contents of tortoise and turtle
pellets are shown in Tables 3 and 4. Four tortoise
feed labels did not declare Ca and P contents. From
the remaining 3 pellets, two had signicantly lower
(B2 and C1) and one signicantly higher (B1) Ca
level than the declared value. The P concentrations
were also signicantly lower than those declared
on the label (B1, B2 and C1). The Ca:P ration was
approximately the same in all pellets.
Feed CP %
label1
CP %
own2
CF %
label
CF %
own
EE %
label
EE%
own
CA %
label
CA %
own
NFE %
own
A10.0 12.9±0.17* 14.0 16.3±0.37* 2.0 1.4±0.15* 6.0 6.0±0.08 63.4
B1 18.1 16.6±0.21* 9.3 3.0±0.32* 3.4 1.9±0.23* 8.0 7.3±0.14* 71.2
B2 14.8 20.5±0.24* 13.3 4.9±0.29* 4.8 3.3±0.08* 6.3 5.5±0.16* 65.8
C1 14.0 14.2±0.08 20.0 21.5±0.52* 2.0 2.6±0.24* 14.0 13.2±0.35* 48.2
C2 12.5 10.9±0.12* 22.0 24.9±0.48* 2.5 1.9±0.18* 8.5 9.6±*0.25 52.7
D9.0 13.8±0.22* 26.0 19.8±0.59* 2.0 2.5±0.28* 10.0 7.7±*0.12 56.2
E1 9.0 12.2±0.16* 22.0 24.5±0.65* 0.5 2.2±0.32* 10.0 7.8±*0.04 53.3
Table 1: Nutrient content of the complete tortoise pellets on dry matter basis
Capital letters indicate the different manufacturing companies. A = Nutrin-Aquarium Tortoise Sticks; B1 = Sera Raffy Vital Her-
bivor; B2 = Sera Reptil Herbivor, C1= JBL Herbil; C2 = JBL Agivert; D = Exo Terra European Tortoise Adult; E1 = Tetra Tortoise.
CP = crude protein, CF = crude bre, EE = ether extract, CA = crude ash, NFE = nitrogen-free extract, 1label information; 2own
analysis; NA = not available; *signicant difference (p<0.05)
139139
Evaluation of commercial tortoise and turtle feeds
Table 2: Nutrient content of the turtle pellets and feeds on dry matter basis
Feed CP %
label1
CP %
own2
CF %
label
CF %
own
EE %
label
EE%
own
CA %
label
CA %
own
NFE %
own
C3 40.0 36.8±2.51* 0.5 2.4±0.28* 7.00 6.9±0.22 8.0 7.6±0.16 46.4
C4 NA 38.5±3.04 NA 3.2±0.22 NA 5.8±0.24 NA 8.1±0.05 44.4
C5 NA 30.2±1.67 NA 1.6±0.23 NA 3.9±0.15 NA 6.9±0.08 57.4
E2 39.0 36.2±3.25* 2.0 0.5±0.18 4.5 2.7±0.07* NA 11.6±0.17 49.0
E3 47.0 55.9±2.34* 4.0 0.05±0.04 7.0 5.8±0.18* 15.0 11.7±0.22* 26.5
E4 45.0 46.9±3.58* 2.0 0.05±0.05 8.0 5.5±0.04* NA 11.6±0.1 35.9
F25.0 27.3±1.28* 2.0 0.9±0.18 1.50 0.4±0.12* 7.0 3.1±0.04* 68.3
LBF NA 64.7±3.64 NA NA NA 10.0±0.31 NA 10.3±0.26 NA
Shrimp NA 70.7±0.15 NA NA NA 2.3±0.12 NA 17.3±0.28 NA
Gammarus NA 49.4±0.14 NA NA NA 5.2±0.24 NA 19.2±0.24 NA
Fish** NA 67.7±0.16 NA NA NA 12.9±0.28 NA 16.2±0.14 NA
Capital letters indicate the different manufacturing the companies. C3 = JBL Agil; C4 = JBL Tortil; JBL = Rugil; E2 = Tetra Rep-
toMin Sticks; E3 = Tetra ReptoMin Energy; E4 = Tetra ReptoMin Baby, F = Panzi. NA = not available; 1label information; 2own
analysis; LBF = lyophilised beef heart, *signicant difference (p<0.05), ** whole frozen sh, European smelt (Osmerus eperlanus);
CP = crude protein, CF = crude bre, EE = ether extract, CA = crude ash, DM = dry matter
Table 3: Calcium and phosphorus content of complete tortoise pellets on dry matter basis
Feed Ca %
label1
Ca %
own2
P %
label
P %
own
Ca:P
own
ANA 1.3±0.06 NA 0.4±0.02 3.2:1
B1 1.5 2.3±0.01* 0.6 0.5±0.01* 4.6:1
B2 2.5 1.2±0.04* 0.7 0.3±0.02* 4:1
C1 2.1 1.3±0.03* 0.6 0.4±0.02* 3.2:1
C2 NA 1.1±0.02 NA 0.4±0.01 2.7:1
DNA 1.2±0.05 NA 0.4±0.02 3:1
E1 NA 1.0±0.02 NA 0.2±0.01 2:1
Capital letters indicate the different manufacturing companies. A = Nutrin-Aquarium Tortoise Sticks; B1 = Sera Raffy Vital Her-
bivor; B2 = Sera Reptil Herbivor, C1= JBL Herbil; C2 = JBL Agivert; D = Exo Terra European Tortoise Adult; E1 = Tetra Tortoise.
1label information; 2own analysis; NA = not available; *signicant difference (p < 0.05)
Table 4: Calcium and phosphorus content of turtle pellets and feeds on dry matter basis
Feed Ca %
label1
Ca %
own2
P %
label
P %
own
Ca:P
own
C3 NA 1.5±0.04 NA 1.1±0.01 1.4:1
C4 NA 1.6±0.04 NA 0.9±0.02 1.8:1
C5 NA 1.5±0.03 NA 1.0±0.02 1.5:1
E2 3.3 3.6±0.06 1.2 1.4±0.01 2.6:1
E3 NA 2.4±0.05 NA 1.3±0.01 1.8:1
E4 3.2 3.6±0.04 1.3 1.5±0.01 2.4:1
FNA 0.3±0.01 NA 0.4±0.00 0.7:1
LBF NA 2.5±0.05 NA 2.0±0.02 1.2:1
Shrimp NA 3.9±0.03 NA 1.3±0.01 3:1
Gammarus NA 5.0±0.02 NA 1.5±0.02 3.3:1
Fish* NA 5.1±0.02 NA 3.3±0.01 1.5:1
Capital letters indicate the different manufacturing companies. C3 = JBL Agil; C4 = JBL Tortil; JBL = Rugil; E2 = Tetra ReptoMin
Sticks; E3 = Tetra ReptoMin Energy; E4 = Tetra ReptoMin Baby, F = Panzi. NA = not available; 1label information; 2own analysis;
LBF = lyophilised beef heart; *whole frozen sh, European smelt (Osmerus eperlanus)
140140 N . Hetényi, E. Andrásofszky
In the case of the turtle pellets our own data
differed signicantly (p<0.05) from the label
information on several occasions. The labelling
of products was also very poor, lacking the
declaration of nutritive value and mineral content
in 2 pellets and 3 other commercial feeds. The CP
was signicantly lower in two pellets (C3 and E2)
and higher in three pellets (E3, E4 and F) than the
label information. The CP content of lyophilised
beef heart, shrimp, Gammarus and sh was the
highest. The CF levels were signicantly lower than
the declared values with one exception (C3). The
EE was approximately the same as the label data
for one pellet (C3) but signicantly lower in the case
of the others. The EE content of lyophilised beef
heart and sh was much higher than that of the
other feeds. The CA was signicantly lower than
the declared value in two pellets (E3 and F). The
NFE contents varied between 26.5–68.3%. Three
pellets with >45% NFE contained cereal grains as
the main ingredient (C3, C5, F). In two pellets (E2
and E3) cereal grains were not mentioned but it
was not specied what ‘ingredient of plant origin’
meant. Pellet E2 had 49% NFE content which
presumably means cereal grain content. Pellets
C4 and E4 also listed cereal grains but not as a
main ingredient.
The Ca and P contents were not declared in
4 pellets and 4 other commercial feeds. Both
of the remaining 2 pellets had higher Ca and
P concentrations than indicated on the label.
Shrimp, Gammarus and whole sh had much
higher Ca content than the other feeds. The P
level of dried invertebrates was similar to that of
the pellets while lyophilised beef heart and sh
contained more P. The Ca:P ratio showed bigger
differences than that of the tortoise pellets.
One pellet (F) had a very disadvantageous ratio
(0.7:1) which can be explained by the extremely
low (0.3±0.01%) Ca content. The Ca:P ratio of
lyophilised beef heart and sh was similar to that
of the pellets with one exception (F), while shrimp
and Gammarus had much higher Ca:P ratios.
Discussion
The diet for captive chelonians should resemble
their wild diet. Herbivorous reptiles cover their
energy requirement mainly by carbohydrates
(50–75% DM), of this 15–40% is the CF. Protein
represents 15–35% and fat is less than 10% (14).
This composition highly depends on the tortoise
species. For captive tortoises it is better to reduce
the protein intake and increase the bre in order
to reduce the growth rate. This diet may include
garden weeds (e.g. dandelion, chickweed), dark
leafy greens (e.g. mustard green, turnip top,
kale, rugula, corn salad) and a small amount of
vegetables (19). Tortoises fed with a diet containing
less than 80% grasses and weeds in the summer
tend to develop pyramidal growth syndrome (20).
Fruits should be avoided or reduced to a minimum
(<5%) because of their high carbohydrate content
(14, 19). Some species may receive higher amount
of fruits which ts their natural diet (e.g. red-
footed tortoise [Chelonoidis carbonaria]; 21).
The natural diet of herbivorous chelonians is
low in CP (approx. 15% DM; 13); however, they
occasionally ingest protein of animal origin (8, 12,
22). Excess protein intake leads to accelerated
growth rate, renal failure, gout and it is also
associated with pyramidal growth syndrome (1,
15, 23, 24, 25). Captive chelonians may have even
lower protein intake to reduce their growth rate.
Five pellets met the CP requirement while one (B1)
had a slightly higher level. The 20.5% CP content
of pellet B2 seems to be too high for pet chelonians
and thus it is not recommended.
Little is known about the fat requirement of
tortoises, but it should be around 3% DM (23).
The EE contents were generally lower than
indicated on the label, but they probably cover the
requirement. However, it is not known whether
the 1.4% EE content of pellet A is sufcient if the
pellet is used as the only feed.
The carbohydrate content should be around
45.5–52.3% (23). Most feeds met this requirement
with three exceptions. Pellets A and B2 had
approximately 10% higher NFE content while
B2 had a much higher NFE concentration than
optimal. Carbohydrate overload also accelerates
the growth rate. It is also important to mention
that some species such as the steppe tortoise
(Testudo horseldi) have very low activity and
spend very little time foraging (<15 min per day;
27). Thus, these chelonians can satisfy their
energy requirement with a modest feeding effort.
In nature, herbivorous tortoises consume a wide
range of plant species (10, 12, 13, 23, 27, 28, 29).
These are typically high in CF (15–40% DM) and
calcium. The high CF content of diets for captive
reptiles is important for reducing the feed intake
and thus the growth rate (28, 30, 31, 32). Captive
141141
Evaluation of commercial tortoise and turtle feeds
reptiles grow much faster than free-ranging ones
(2, 3, 15, 25, 33, 34). In the diet of Galapagos giant
tortoises (Geochelone nigra), CF may reach 30–
40% on DM basis which might be the case in other
herbivorous chelonians as well (29). In the diet of
captive desert tortoise (Gopherus agassizii) the CF
level can be 25–30% (35). Some species (e.g. the
Bolson tortoise [Gopherus avomarginatus]) feed
on droppings of rabbits which are high (30% DM)
in undigested bre (36) and can serve as a source
of trace elements as well. Herbivorous chelonians
rely on gut microbes to ferment dietary bre and
produce volatile fatty acids (14, 37, 38). It seems
that they can digest cellulose and hemicellulose
as efciently as herbivorous mammals (32, 39).
Pellets A, B1 and B2 did not contain an adequate
amount of CF. Four pellets (C1, C2, D and E1)
reached the recommended minimum level but
pellet D contained much less CF than the declared
value (19.8 vs. 26% DM).
The natural diet is rich in Ca and tortoises feed
on soil, bones, or faeces of carnivores to full their
Ca requirement (12, 36, 40, 41, 42). Tortoises
have high Ca tolerance which can be explained
by the fact that these animals grow until death
(43). Higher Ca intake also leads to enhanced Ca
digestibility (44, 45). In 6 pellets (A, B2, C1, C2,
D and E1) the Ca concentration was around 1%
which seems to be too low.
The optimal Ca:P ratio of tortoise diets is much
higher (3.1–5.8:1 or even higher; 46) than the
general recommendations for mammals (Ca:P =
2:1). According to experimental data this ratio
may reach 6:1 without causing adverse effects
(1.29% Ca on a dry matter basis; 44). In the diet
of wild juvenile and adult desert tortoises the Ca:P
ratio of needlegrasses (Achantherum spp.) is 22:1
and 13:1, respectively, while desert dandelion
(Malacothrix spp.) forbs have a ratio of 9:1 and
14:1, respectively (9). In some plant species the
Ca:P ratio may reach 32.4:1 (Cardus australis;
13). Five pellets reached or exceeded the minimum
recommendation for Ca:P and two pellets (C2 and
E1) were below that.
Carnivorous aquatic chelonians have much
higher protein and fat requirements than
herbivores while their bre and carbohydrate
requirements are much lower (12, 47). Whole
frozen sh can be a reference feed which is
available in pet shops. Freezing has the advantage
that it eliminates parasites. It is advised to feed a
variety of sh species to avoid the possible long-
term negative effects of the exclusive feeding of
one species. For example, smelt may have high
thiaminase activity and can induce thiamine
deciency (48). Whole sh should be fed frequently
to most freshwater turtles and should be the main
feed for piscivorous species (14, 47, 48 49, 50,
51). Besides that, other whole vertebrates and
invertebrates such as shrimp or Gammarus can
be offered. Carnivorous reptiles mainly cover their
energy requirements from protein (25–60%) and
fats (30–60%), which highlights the importance
of these nutrients. Carbohydrates have the
lowest importance with less than 10% DM (12).
Many of the freshwater turtles are opportunistic
carnivores or omnivores, as they undergo an
ontogenetic shift in their diet as they mature (6,
11, 14, 51, 52, 53, 54, 55, 56, 57, 58). This dietary
shift can be explained by the hypothesis that
larger turtle species are less able to meet their
metabolic requirements on a carnivore diet, have
greater capacity to store fats and can cover their
energy requirements on a plant diet as well. Diet
change is also linked to changes in physiological
needs and specic requirements (51, 59, 60).
Specialities can be mentioned as adult pond
sliders (Trachemys scripta) become predominately
herbivorous; the animal to plant matter ratio in
their diet is 77:23 (54). Carbohydrates are more
important for omnivorous reptiles (20–75% DM),
while fats represent 5–40% and protein is between
15–40% (14).
The CP levels of pellets were much lower
than those of sh or dried invertebrates. The
recommended protein level for Chinese softshell
turtle (Pelodiscus sinensis) is 39.0–47.7% DM (61,
62, 63, 64, 65, 66, 67, 68). In red-eared terrapins
(Trachemys scripta elegans) a growth rate equal
to the natural one was obtained with 25–40% CP
(50). When turtles are kept as pets and not as
farmed animals the protein concentrations may be
lowered to prevent fast growth rate (69), but exact
recommendations are missing. Sudden overfeeding
with protein may lead to dysbiosis and diarrhoea
while prolonged overfeeding results in obesity (49).
This is why overfeeding with whole sh should be
avoided by applying adequate feeding frequency.
Juveniles and breeding females have much higher
protein requirements (53, 66, 68), the latter may
reach 61–66% (69). Too low (<30%) protein intake
of growing turtles may lead to reduced growth
rate (50, 64, 70). The animal:plant protein ratio
of the diet should be around 3:1 (61). With one
142142 N . Hetényi, E. Andrásofszky
exception (F), these commercial pellets may cover
the requirements of slow-growing adults as these
turtles may be fed moderate CP levels of around
26%. Pellets C5 and E4 were dedicated to young
growing animals. Product E4 with its 46.9% CP
content may cover the requirement but product
C5 with 30.2% seems to be inadequate.
Because of packaging and storage, it is better
to have pellets with lower EE content, but this
macronutrient is important in the energy supply
of carnivorous and omnivorous turtles (14). As
Table 2 shows, the EE levels of pellets were much
lower than that of the frozen sh (12.9% DM).
The recommended EE level for Chinese softshell
turtle in commercial farms is around 4.2–8.8%
(74, 64, 65, 66, 67, 68, 70, 71, 72). High-fat diets
(13.9% EE) should be avoided as they lead to
the accumulation of lipids in the liver and liver
injury (65). The optimal EE intake for pet turtles
is not known but presumably it may be lower.
Accordingly, it seems that most of the pellets can
cover the EE requirements. Pellet F with 0.4% EE
content is an exception. Although it is called a
‘complete feed’, it does not cover the requirement
of the animals. Based on the EE content of whole
sh, especially the European smelt, moderate and
not exclusive feeding is recommended as part of a
balanced diet.
The NFE requirement of turtles may vary
according to their specic requirements. If we
calculate with 39–46% CP, 9% EE and 4% CF for
carnivorous turtles, then the NFE is approximately
41–46%. This seems to be adequate for carnivores
(61, 64) and the optimal starch content for farmed
juvenile soft-shelled turtle is around 30% (71).
Opportunistic carnivores may have higher NFE
requirements.
Little is known about the CF requirements
of carnivorous or opportunistic carnivorous
chelonians. Feeds of animal origin do not contain
CF, thus it may only be important for opportunistic
carnivores. On the other hand, bre has a satiating
effect which helps to avoid overfeeding and may
have a benecial effect on the gut microbiota of
pet turtles. For juvenile soft-shelled turtles 2–8%
CF seems to be adequate (71).
The Ca and P contents of the pellets and
lyophilised beef heart were much lower than
those of Gammarus and whole sh. Imbalanced
diets having low Ca content lead to metabolic
bone disease of nutritional origin in aquatic
turtles as well (73). However, excess Ca intake
(2.24% DM) may have a negative impact on the
growth rate of aquatic turtles (74). On the other
hand, the optimal Ca and P intake for Chinese
softshell turtle is 5.7% and 3.0%, respectively
(75). These data are very similar to the Ca and
P levels of European smelt. Metabolic bone
disease of nutritional origin can be prevented
by providing 1.16–2.95% Ca and 0.92–2.56% P
in the diet (74). Shrimp, Gammarus and whole
sh are good Ca sources. As aquatic turtles
feed underwater, dusting the feed with dietary
minerals and vitamin supplements does little
to cover the requirements. Therefore, the diet
should have optimal Ca and P content.
According to studies on Chinese softshell turtle,
the Ca:P ratio should be approximately 2:1. This
can be reached with 5.7% Ca and 3.0% P (60). The
lower Ca:P ratio may lead to shell malformations or
lower growth rates. This recommended ratio was
reached only in pellets E2 and E4. The Ca:P ratio
of European smelt is lower than 2:1 but close to
the 1.9:1 ratio recommended for Chinese softshell
turtle (75). Shrimp and Gammarus have much
higher Ca:P ratio than the minimum requirements;
thus, they can be fed in combination with whole
sh to increase the Ca:P ratio.
Conclusion
As a general recommendation, we suggest
not to buy any commercial feed that does not
have detailed nutritional values. For herbivorous
tortoises a good-quality pellet should be low
in protein (10–15%), high in crude bre (18–
20%) and its Ca:P ratio should be >3:1. Avoid
feeds containing proteins of animal origin.
According to the nutritional values determined
by our own analysis, products C2 and E1 can
be accepted but their Ca:P ratios were far from
the requirements. Thus, none of the commercial
feeds is recommended for use as main feed.
The nutrient content of the pellets should be
checked very carefully, as label information is
not necessarily precise. For carnivorous turtles
the nutrient content of articial feeds should be
close to the nutritive value of whole sh or the
recommendations. This means 25–50% protein
(for young growing animals >30%), 4–8% EE and
a Ca:P ratio of >2:1. Based on their CP and EE
levels, four pellets (C3, C4, E3 and E4) can be
accepted, but because of the inadequate Ca:P
ratio only pellet E4 can be recommended.
143143
Evaluation of commercial tortoise and turtle feeds
Based on the nutritive value of the pellets it
is not advised to use them as the only or main
feedstuff. Different chelonian species may have
widely varying requirements, and thus a diet
universally suitable for all of them cannot be
formulated. Greater emphasis should be put on
the proper labelling of products.
Acknowledgments
The authors declare that they have no conicts
of interest. The authors declare that they
have no afliations with or involvement in any
organization or entity with any nancial interest
in the subject matter or materials discussed in
this manuscript.
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147147
Evaluation of commercial tortoise and turtle feeds
VREDNOTENJE KOMERCIALNIH ŽELV IN KRME ZA ŽELVE
N. Hetényi, E. Andrásofszky
Izvleček: Želve v ujetništvu je potrebno hraniti z naravno krmo, da dosežejo podobno stopnjo rasti kot živali v prosti reji. Na voljo
je širok izbor komercialno pripravljene hrane za želve. Prednost hranjenja želv s komercialno hrano je priročnost, vendar podatki
o prehranskih potrebah za posamezne vrste želv še niso na voljo. Namen te raziskave je bil analizirati in ovrednotiti komercialne
pelete in krmo za želve. V trgovinah za živali smo od 6 podjetij kupili komercialne pelete (npeleti za vodne želve = 7, npeleti za kopenkse želve = 7) za
mesojede vodne in rastlinojede kopenske želve ter drugo kr mo za vodne želve (liofilizirano goveje srce, posušene vodne nevre-
tenčarje in zamrznjene cele ribe). Zamrznjene cele ribe smo uporabili kot referenčno krmo za mesojede vodne želve. Določili smo
kemično sestavo in vsebnost kalcija (Ca) ter fosforja (P). Za ničelno hipotezo smo uporabili T-test enega vzorca s podatki na etiketi
in rezultate lastne paralelne analize za surove beljakovine (an gl.
crude proteins, CP
), ekstrakt etra (angl.
ether extract, EE
), surovo
vlaknino (angl.
crude fibre, CF
), Ca in P. Oznake nekaterih peletov so bile pomanjkljive, saj so manjkali podatki o hranilnih vred-
nostih, Ca in P (npeleti za kopenske želve = 4 od 7, n
peleti za vodne želve
= 5 od 7). Podatki na etiketi so se bistveno razlikovali (p < 0,05) od rezultatov
naše analize pri 13 od 14 vrst peletov. Nobeni peleti za kopenske želve niso v celoti izpolnjevali potreb živali. Zaradi neustreznega
razmerja Ca : P smo kot ustrezno določili le eno izmed 7 vrst peletov za vodne želve, zaradi česar nobenih od komercialnih peletov
nismo določili kot priporočljivih za glavno ali edino krmo za želve.
Ključne besede: prehrana; peleti; presnovna bolezen kosti; želve
