compare the levels of macroelements (Ca, P, K, Na, Mg), microelements (Fe, Zn, Mn, Cu), heavy metals

Overview

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Key numbers

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1 Department of Monogastric Animal Sciences, Division of Animal Nutrition and Food, West Pomeranian
University of Technology in Szczecin, 29 Klemensa Janickiego, 71270 Szczecin, Poland;
2 Department of Agroecology and Crop Production, University of Agriculture in Krakow, 21 Mickiewicza,
minimum recommended levels for protein and fat. Eighteen tested dog foods (60%) did not meet at
Association (APPA) (1), in 2018 67% of U.S. households, i.e., an estimated 84.9 million homes, owned at
least one pet. In Europe this figure is estimated at 38% of all households (85 million homes) (2).
health and welfare. The European Pet Food Industry Federation (FEDIAF) (3) established nutritional
guidelines, based on the recommendations of the National Research Council (4) and scientific research.
the proper functioning of the muscular and nervous system of dogs (5). Potassium and sodium are
in the blood (6). Nutritional guidelines provide minimum and, in some cases, maximum recommended
Molecules 2020, 25, 5173; doi:10.3390/molecules25215173 www.mdpi.com/journal/molecules
Their quantities in dog food should be monitored and are verified in scientific research (7–13), as it is
important for animal heath safety (14–16).
While major macroelements and trace elements in pet foods are regulated by the US NRC (4),
documenting the presence of heavy metals in pet food (18–20). Higher levels than normal probably
over time (21). Contemporary pet food formulations use various foods as their main ingredients,
food sector (22,23). For many years the phrase “grain-free” has been widely used in pet food market.
animals as a foodstuff, or processed for food or industrial purposes (24). On the basis of the Encyclopedia
of Grain Science (24) grains include, among others, green beans, sugar peas, lupins, amaranth, and linseeds.
Most domestic dogs in industrialized countries are fed extruded dog food (25). The information
2.1. Basic Composition
FEDIAF (3), which are 18 g and 5.5 g/100 g of dry matter (DM) of food, respectively (Table 1).
The analyzed dog foods differed in the content of protein and ether extract (range 21.4–38.97 and
6.31–21.39 g/100 g DM, respectively). Crude fiber content varied in analyzed food and ranged from
2.9 to 15.14 g/100 g DM. Crude ash ranged from 4.8 to 9.92 g/100 g DM. Carbohydrate content (defined as
17.74 to 53.17 g/100 g DM. The metabolizable energy (ME) content in the dog foods also varied and
ranged from 347 to 415 kcal ME/100 g DM. Differences in protein, fat, fiber, ash, and NFE content were
had more crude protein (+19%), fat (+30%), fiber (+33%), and ash (+11%) than foods with cereals.
In turn, cereal foods had more NFE (+32%) than cereal-free dog foods.
Table 1. Nutrients (g/100 g DM) and energy value (kcal/100 g DM) content of the studied dry dog foods 1 .
No 2 Ether Extract Crude Fiber Crude Ash NFE 3 ME 4
2 92.85 fghi 28.14 ijkl 11.61 cdefg 5.59 cdefg 7.78 o 39.74 efg 376.0 defghi
3 92.86 ghi 24.40 cd 9.82 bcdef 5.71 defgh 7.74 o 45.21 hijk 366.8 cde
4 92.45 cde 29.42 lm 12.26 efgh 7.30 ghijk 5.92 cd 37.56 def 378.2 defghi
5 92.46 cde 25.71 def 8.02 ab 5.83 defghi 9.92 r 43.00 gh 347.0 a
6 92.45 cde 28.27 ijkl 14.74 hijklm 5.94 defghi 6.74 jk 36.77 de 392.8 jklmnop
7 93.60 k 26.05 efg 14.72 hijklm 4.12 abcde 6.07 cde 42.65 gh 407.2 pq
9 94.51 n 22.73 ab 9.82 bcdef 8.07 hijkl 4.93 a 48.96 jklm 375.1 cdefghi
12 97.39 r 38.07 o 16.49 klmno 4.32 bcdef 9.88 r 28.64 b 415.2 q
13 96.34 p 25.14 cde 11.81 efg 6.59 fghij 7.19 lmn 45.61 hijk 389.3 ijklmno
14 95.95 o 24.29 cd 11.84 efg 6.52 efghij 8.56 p 44.75 hij 382.7 fghijk
15 93.48 jk 28.91 jklm 8.89 abc 6.39 efghij 7.08 lm 42.23 gh 364.5 bcd

Methods (brief)

performed using an atomic absorption spectrometer. All the evaluated dry dog foods met the
metals in commercial pet food samples available in Turkey, although their concentrations appeared
However, Al, Sb, and U were present in some samples above the maximum levels established for humans.
samples provide a snapshot of European dry dog foods from different market segments.
analyzed dog foods is shown in Table 5. All samples were packaged in sealed bags. After opening,
from three packages of individual dog foods samples were collected, in order to obtain one representative
sample for chemical analysis. The samples were then ground into powder using a laboratory mill
samples were dried at 105 ◦ C to constant weight. Crude protein (N × 6.25) was identified by the Kjeldahl
digestion in concentrated sulfuric acid (H2 SO4 ) and perchloric acid (HClO4 ). Analyses for Ca, K,
Na, and Mg were performed using an atomic absorption spectrometer (Thermo Fisher Scientific iCE
(Carl Zeiss Jena, Germany). The absorbance value of the sample determined spectrophotometrically,
analyses was subjected to digestion in a nitric acid (HNO3 ) and perchloric acid (HClO4 ) mixture.
Analyses were performed using an atomic absorption spectrometer (Thermo Fisher Scientific iCE
cryogenic grinding and quantitation by ICP-MS, Part I. Spectroscopy 2011, 26, 46–68.
cryogenic grinding and quantitation by ICP-MS, Part II. Spectroscopy 2011, 26, 42–59.
gastric digestions. Food Chem. Toxicol. 2013, 55, 568–577. (CrossRef) (PubMed)
feeds using direct solid sample analysis by HR-CS GF AAS. Microchem. J. 2017, 133, 524–529. (CrossRef)
1. Tsanaktsidou, E.; Zachariadis, G. Titanium and chromium determination in feedstuffs using ICP-AES

Implications

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Update history

The five most recent substantive edits to this page, classified major (evidence or structure moved), correction (a published value or statement was wrong and has been fixed), or minor (narrative rewritten without changing the underlying evidence). Each description is derived from what the edit did to this page; the linked commit is the authoritative record, routine regeneration passes are excluded, and the full version history lives in git. When DOI minting comes online (see schema docs), each entry below will also link to a version-pinned DataCite DOI.

Commit	Date	Change	Description
3171d06	2026-08-02	major	1 section added
bc84bfc	2026-08-02	major	6 sections added; narrative text revised