Fatty Acid Analysis and Stability of Selected Edible Oils Used in Homemade Pet Diets

ABSTRACT

Background

Edible oils often are included in recipes for home‐prepared pet diets to supply essential fatty acids, but there may be discrepancies between database values and oil profiles. Furthermore, storage time and conditions influence quality.

Hypothesis/Objectives

Determine the fatty acid profiles of commonly used oils and characterize fatty acid oxidation under recommended storage conditions.

Samples

Fourteen products were purchased and stored according to label instructions, representing 2 brands each of walnut, corn, canola, and flaxseed oils, and 3 each of safflower and sunflower oils.

Methods

Samples were collected at baseline and at 6 and 12 months and stored at −80°C until analysis. Aliquots were analyzed for fatty acid profile at baseline and 12 months, and at all 3 timepoints for free fatty acidity, peroxide value, and induction time.

Results

Linoleic acid concentrations exceeded the United States Department of Agriculture (USDA) Food and Nutrient Database for Dietary Studies (FNDDS) values except for 2/3 sunflower and 1/3 safflower oil samples. Peroxide value was static for 3/14 products and significantly increased at 6 or 12 months for 11/14 products. Induction time was static for 2/14 products and significantly decreased at 6 or 12 months for 12/14 products.

Conclusions and Clinical Importance

Sunflower and safflower oils are not reliable sources of linoleic acid. Cold storage appeared to better maintain oil quality. Oils for home‐prepared pet foods should be carefully selected to ensure nutritional adequacy and refrigerated to maintain quality, especially those high in polyunsaturated fatty acids, high omega‐6:omega‐3 ratios, or both.

Abbreviations

ALA

alpha linolenic acid

FFA

free fatty acidity

FNDDS

food nutrient database for dietary studies

GC‐FID

gas chromatography flame ionization detector

LA

linoleic acid

MUFA

monounsaturated fatty acids

PUFA

polyunsaturated fatty acid

USDA

United States Department of Agriculture

1. Introduction

The formulation of home‐prepared diet recipes for pets is a computer‐dependent process and typically integrates one or more food databases of nutritional profiles, including the United States Department of Agriculture (USDA) Food Data Central database [1]. Edible plant oils are commonly used to supply dogs and cats with linoleic acid (LA), the essential omega‐6 polyunsaturated fatty acid (PUFA), as well as alpha linolenic acid (ALA), an essential omega‐3 PUFA [2]. However, some products may not meet the label claims of fatty acid content or database entries may not reflect their composition. Plant breeding practices as well as technologies related to oil processing and genetic engineering generally have favored the development of seed and nut oils lower in PUFA to increase stability during heating [3, 4, 5, 6]. Therefore, nutrient amounts as reflected by database values may not match what is commonly available to pet owners.

Another important consideration is the quality and stability of nutrients in home‐prepared pet diets. Importantly, because of their chemical structure, PUFA are uniquely sensitive to degradation over time caused by oxidation, which negatively impacts quality in terms of fatty acid stability as well as palatability (rancidity). This effect may result in losses of essential nutrients, formation of harmful chemical components, and general quality degradation. Oil oxidation also may result in negative health effects described in people [7]; to date, similar research has not been performed for pets. The production of various harmful chemical components as well as oxidation damage in edible oils used for high heat frying and similar applications are well described [8, 9, 10, 11], but such changes also have been documented under more moderate environmental conditions for vegetable oils [12, 13]. Standardized quality variables are well accepted for edible oils, including analysis for free fatty acidity (FFA), peroxide values, and induction time [14, 15, 16, 17, 18, 19, 20]. Free fatty acidity is a parameter of hydrolysis, is associated with oxidation susceptibility and rancidity, and is expressed as % oleic acid/total fatty acids. Peroxide value is a measurement of hydroperoxide content as an indicator of primary oxidation status; it is expressed as mEq O₂/kg oil. Induction time is a measurement of time until oxidative reaction, which correlates with shelf life and is expressed as hours, where higher values indicate more stable products.

Our objectives were to analyze and quantify the fatty acid profiles of selected edible oil products and compare the values with those declared by the label and as represented in the USDA Food Data Central database and by the Codex Alimentarius International Food Standards for Named Vegetable Oils [1, 21]. We also aimed to determine the stability of selected edible oil products as measured by FFA, induction time, and peroxide values at baseline and after 6 and 12 months of storage.

2. Materials and Methods

Fourteen edible oil products were purchased from local grocery stores and online. Two brands were purchased each of walnut, corn, canola, and flaxseed oils, and three each of safflower and sunflower oils. The safflower and sunflower oils included one product each with a label claim for high LA content.

Samples were collected from each product container at baseline and at 6 and 12 months. All samples were kept in freezer storage at −80°C until analysis, which was completed within 8 weeks of the final time point. In between sample collections, products were maintained in a temperature‐controlled laboratory inside an enclosed cabinet (n = 10; 21.9°C–22.6°C) or refrigerated if specified on the label (n = 4; 2.5°C–5.5°C).

Fatty acid profiles were determined in duplicate samples at baseline and 12 months. The sample preparation followed the International Olive Council official method (COI/T.20/Doc. no. 24–2001): approximately 30 mg of oil sample was dissolved in 3 mL hexane before 0.2 mL of 2 M methanolic potassium hydroxide was added. The upper layer then was filtered through a polytetrafluoroethylene membrane for analysis on a gas chromatography flame ionization detector (GC‐FID). The instrument condition was as described previously [22]. Briefly, the separation was achieved on a 90 m × 250 μm × 0.25 μm DB‐FastFAME capillary column (Agilent Technologies) with a helium carrier gas at 1.9 mL/min. The injection volume was 1.0 μL with a split ratio of 30. Gas chromatography inlet temperature was 260°C; GC oven program initially was held at 75°C for 1 min; then ramped at 35°C/min to 200°C and held for 14 min followed by a ramp of 2.5°C/min to 210°C and held for 5 min before ramping up to 230°C at 12°C/min and held for 20 min; flame ionization detector (FID) temperature was 260°C. The detector gas consisted of hydrogen (40 mL/min), air (400 mL/min), and nitrogen make‐up gas (25 mL/min). Peak identification was performed using a 37‐component fatty acid methyl ester reference standard mix (Sigma‐Aldrich). Concentrations of fatty acids were compared to the entries in the USDA FoodData Central database, focusing on comparisons to the entries in the Food Nutrient Database for Dietary Studies (FNDDS), because these are most complete and regularly updated [1].

Quality and stability parameters were evaluated at baseline, 6 and 12 months, including FFA (American Oil Chemists' Society [AOCS] official method Ca 5a‐40), peroxide value (AOCS official method Cd 8b‐90), and induction time (AOCS official method Cd 12b‐92; temperature at 110°C; air flow rate at 20 L/h). Where relevant, fatty acid composition as well as quality and stability parameter values were compared to thresholds established by Codex Alimentarius International Food Standards for Named Vegetable Oils or the United States Pharmacopeia Food Chemical Codex [21, 23]. Codex standards are voluntary and not legally binding, except when incorporated into food regulations of specific jurisdictions, and they have been included in various global trade agreements.

2.1. Statistics

All data are expressed as mean ± SD. One‐way analysis of variance followed by Tukey and Dunnett multiple comparisons were applied using XLSTAT (Microsoft Excel 2023/XLSTAT, Version 2023.3.0, Addinsoft Inc., Denver, CO, USA) to evaluate significant differences in the evolution of each quality parameter (FFA, peroxide value, and induction time) during storage for each oil sample, as well as the significance of quality parameters at each time point (T0, T6, and T12) among different oil samples. For all comparisons, differences were considered significant at a value of p < 0.05. Fatty acid composition and quality parameters were processed for principal component analysis to visualize the correlations between oils and chemical parameters at T12.

3. Results

3.1. Product Details

No products included antioxidants in the ingredient declaration. The “best by” dates for 3 products fell between the 6‐ and 12‐month timepoints (two sunflower and one flaxseed). Label claims included non‐genetically modified (9/14 products), organic (5/14 products), refined (3/14 products), pure (4/14 products), cholesterol‐free (4/14 products), high heat or a specific listed smoke point (6/14 products), and fatty acid (FA) content claims (specific FA amounts, FA categories such as “n3” or trans fat, or qualitative “high in” claims; 11/14 products). Other miscellaneous claims included gluten‐free, vegan, kosher, neutral flavor, heart‐healthy, bisphenol A‐free, hexane‐free, chemical‐free, “pure and unrefined”, “great for skin, hair, and frying”, and cold or expeller pressed. Costs for products ranged from $0.003 to $0.047 per mL (mean, $0.021 per mL).

3.2. Fatty Acid Profiles and Comparisons to Database Values, Label Claims, and Codex Standards

Analysis values for LA and ALA as well as the respective FNDDS values are presented in Table 1. The concentrations in all samples were relatively static between the timepoints.

TABLE 1.

Analyzed percent linoleic acid (LA) and alpha‐linolenic acid (ALA) concentrations of 14 selected edible oils at baseline (T0) and after 12 (T12) months of storage, with comparison to the USDA food nutrient database for dietary studies (FNDDS).

Description	LA analysis T0	LA analysis T12	LA FNDDS	ALA analysis T0	ALA analysis T12	ALA FNDDS
Walnut oil a	63.1 ± 0.0	63.0 ± 0.0	52.9	12.8 ± 0.0	12.8 ± 0.0	10.4
Walnut oil	61.8 ± 0.0	61.7 ± 0.0		12.7 ± 0.0	12.6 ± 0.0
Sunflower oil b	6.2 ± 0.1	6.0 ± 0.0	20.6	0.1 ± 0.0	0.1 ± 0.0	0.16
Sunflower oil	5.4 ± 0.0	5.3 ± 0.0		0.0 ± 0.0	0.0 ± 0.0
Sunflower oil a , b	61.6 ± 0.0	61.3 ± 0.0		0.1 ± 0.0	0.1 ± 0.0
Corn oil	54.1 ± 0.0	54.1 ± 0.0	51.9	1.2 ± 0.0	1.2 ± 0.0	1.04
Corn oil	54.9 ± 0.0	54.8 ± 0.1		0.9 ± 0.0	0.9 ± 0.0
Canola oil	19.4 ± 0.0	19.3 ± 0.0	17.8	7.7 ± 0.0	7.6 ± 0.0	7.45
Canola oil	19.0 ± 0.0	18.9 ± 0.0		7.8 ± 0.0	7.8 ± 0.0
Safflower oil	10.8 ± 0.0	10.7 ± 0.0	13.7	0.0 ± 0.0	0.0 ± 0.0	0.15
Safflower oil	15.1 ± 0.0	14.8 ± 0.0		0.1 ± 0.0	0.1 ± 0.0
Safflower oil	74 ± 0.0	73.7 ± 0.0		0.1 ± 0.0	0.1 ± 0.0
Flaxseed oil a	16.8 ± 0.0	16.8 ± 0.0	14.3	51.1 ± 0.0	51.1 ± 0.0	53.4
Flaxseed oil a , b	15.8 ± 0.0	15.8 ± 0.0		50.1 ± 0.0	50.0 ± 0.0

Note: Values are means ± SD of duplicate samples for each product at each timepoint. Two brands each of walnut, corn, canola, and flaxseed oil were assessed, and three brands each of sunflower and safflower oil.

^a Stored in refrigerator per label instructions.

^b Label “best by” date fell between T6 and T12.

Of the edible oils tested, only flaxseed is a substantial source of ALA (> 50% by weight), but both samples contained ALA in concentrations that were 4.3%–6.4% below FNDDS values. The ALA content of corn, sunflower, and safflower oil samples was negligible in our analyses as well as in the database entries (concentrations of up to approximately 1% by weight). Walnut and canola oils provide only modest amounts of ALA (7.5%–13% by weight), and all four products at both time points exceeded the respective FNDDS values for ALA.

All walnut, corn, flaxseed, and canola oil samples exceeded the LA values in the respective FNDDS entries. One safflower oil product with a label claim for high oleic acid content fell below the database value for LA, whereas the other two safflower oils met the entry (for the “high heat” product) or well exceeded the amount (for the “high linoleic acid” product).

In contrast, compared with the FNDDS entry, two of the sunflower oil products were 70% and 74.3% below the LA concentration; both had claims for high oleic acid content. The third sunflower oil product had a claim for a specific LA amount per serving but did not meet the label claim (analyzed amount 8.3 g LA per serving vs. label claim of 9 g LA per serving) but the concentration of LA was almost three times higher than the FNDDS entry value.

There were several instances of label content claims not corresponding to analyzed fatty acid profiles, which affected nine products. Most discrepancies were minor, including one canola oil sample containing 1.1 g ALA per serving versus the label claim of 1.2 g ALA per serving. In addition, one sunflower oil product claimed 9 g per serving and contained 8.6 g per serving. In other cases, larger discrepancies existed between label claims and analyses for fatty acid categories (saturated fat, PUFA, and monounsaturated fatty acids [MUFA]). For example, both walnut oils were below the claims for saturated fat per serving (5.8%–8% below claims). Also, two sunflower oils, one canola, and one safflower oil were below their respective label claims for PUFA per serving (6%–44% below claims). One walnut oil and one safflower oil were below their respective label claims for MUFA per serving (6% and 21% below claims). The label of one safflower oil product did not provide PUFA or MUFA information and could not be further evaluated.

The fatty acid concentration ranges specified in the Codex matched the analyzed values for all oils except one safflower oil product that exceeded the range for oleic acid and was under the minimum for LA [21]. This oil was likely a “high‐oleic” product not labeled as such.

3.3. Quality Parameters

Free fatty acidity, peroxide value, and induction time assessments are presented in Table 2. According to the Codex Alimentarius thresholds, FFA upper limits are 0.3% oleic acid in refined oil and 2% oleic acid in most cold‐pressed and virgin oils [21]. As shown in Table 2, most oils tested in this study had FFA below the 0.3% limit (for refined oils) with one exception of a sunflower oil at 0.65% (although labeled as “unrefined”). Although product labels only specified that 3/14 products were refined, it is reasonable to conclude that most of the oils in the study were refined unless otherwise stated. As expected, FFA did not change significantly over time in any sample.

TABLE 2.

Quality parameters as determined in 14 selected edible oils at baseline (T0) and at 6 (T6) and 12 (T12) months of storage. ¹

	Free fatty acidity (% oleic acid/total fatty acids)			Peroxide value (meq O2/kg oil)			Induction time (hours)
	T0	T6	T12	T0	T6	T12	T0	T6	T12
Walnut oil 2	0.05 ± 0.01	0.07 ± 0.01	0.05 ± 0.01	3.41 ± 0.01c	5.79 ± 0.07b	9.45 ± 0.26a	3.68 ± 0.1a	3.23 ± 0.02ab	2.91 ± 0.18b
Walnut oil	0.02 ± 0.01	0.03 ± 0.01	0.03 ± 0	4.48 ± 1.51b	13.95 ± 3.68b	27.19 ± 2.42a	2.99 ± 0.27a	2.63 ± 0.29ab	1.88 ± 0.17b
Sunflower oil 3	0.03 ± 0	0.04 ± 0	0.04 ± 0.01	2.16 ± 0.09c	4.51 ± 0.21b	6.5 ± 0.12a	15.77 ± 0.08a	11.02 ± 0.11c	13.57 ± 0.06b
Sunflower oil	0.03 ± 0.01	0.04 ± 0.01	0.03 ± 0	2.51 ± 0.49a	3.79 ± 0.63a	4.93 ± 1.07a	19.45 ± 0.05a	16.77 ± 0.37b	7.27 ± 0.37c
Sunflower oil 2 , 3	0.65 ± 0.01	0.67 ± 0.01	0.65 ± 0	1.69 ± 0.4c	9.4 ± 0.45b	27.47 ± 3.01a	5.26 ± 0.08a	3.99 ± 0.11b	3.53 ± 0.01c
Corn oil	0.04 ± 0.01	0.05 ± 0.01	0.05 ± 0.01	0.55 ± 0.02c	1.49 ± 0.13b	2.43 ± 0.13a	11.15 ± 0.04a	8.64 ± 0.28b	7.77 ± 0.03c
Corn oil	0.03 ± 0.01	0.04 ± 0.01	0.04 ± 0	0.73 ± 0.1c	1.86 ± 0.24b	3.22 ± 0.59a	11.59 ± 0.15a	9.19 ± 0.17b	7.42 ± 0.24c
Canola oil	0.02 ± 0 b	0.04 ± 0.01	0.04 ± 0	0.63 ± 0.04c	3.94 ± 0.07b	11.43 ± 0.19a	8.97 ± 0.34a	5.93 ± 1.15b	6.06 ± 0.2ab
Canola oil	0.05 ± 0.01	0.05 ± 0.02	0.07 ± 0.01	0.93 ± 0.03a	1.13 ± 0.16a	4.9 ± 1.74a	11.04 ± 0.04a	8.99 ± 0.01b	7.98 ± 0.02c
Safflower oil	0.02 ± 0	0.03 ± 0.01	0.02 ± 0	1.3 ± 0.05b	3 ± 0.65a	3.99 ± 0.19a	13.65 ± 0.51a	10.62 ± 1.29a	9.94 ± 1.03a
Safflower oil	0.04 ± 0.01	0.04 ± 0.01	0.04 ± 0	2.02 ± 0.36b	4.75 ± 0.18b	15.46 ± 1.13a	10.16 ± 0.48a	7.7 ± 0.02b	5.73 ± 0.07c
Safflower oil	0.03 ± 0.01	0.04 ± 0.01	0.03 ± 0.01	3.28 ± 0.3c	10.79 ± 0.28b	21.75 ± 0.25a	3.48 ± 0.08a	2.58 ± 0.04b	2.01 ± 0.18c
Flaxseed oil 2	0.13 ± 0	0.14 ± 0.01	0.13 ± 0	0.94 ± 0.11a	1.08 ± 0.6a	1.56 ± 0.91a	2.18 ± 0.03a	1.97 ± 0.01b	2 ± 0.08ab
Flaxseed oil 2 , 3	0.27 ± 0	0.27 ± 0.01	0.27 ± 0.01	0.65 ± 0.04c	2.42 ± 0.1b	3.27 ± 0.2a	2.27 ± 0.01a	2.05 ± 0.11a	2.03 ± 0.02a

¹ Values are means ± SD of duplicate samples for each product at each timepoint. Two brands each of walnut, corn, canola, and flaxseed oil were assessed, and three brands each of sunflower and safflower oil. Different letter superscripts in a row indicate significant changes over time (p ≤ 0.05).

² Stored in refrigerator per label instructions.

³ Label “best by” date fell between T6 and T12.

The Codex Alimentarius International Food Standards for Named Vegetable Oils has peroxide value thresholds for products claiming to be “refined” (up to 10 meq O₂/kg oil) or “cold pressed or virgin” (up to 15 mEq O₂/kg oil). In our study, peroxide value at baseline ranged from 0.55 ± 0.02 to 4.48 ± 1.5 mEq O₂/kg oil among tested samples, which all were well below the limits. Peroxide values were static over time for 3/14 products (one high oleic sunflower oil, one canola oil, and one flaxseed oil specifying cold storage and within “best by” date). Two of three products with a refined claim met the Codex standard at all timepoints, whereas one walnut oil product with a refined claim but not specifying cold storage exceeded the standard at both 6‐ and 12‐month timepoints (Table 2). Two products with a cold pressed claim met the Codex standard for peroxide values at all three time points, but a third well exceeded the threshold at 12 months (unrefined sunflower oil out of “best by” date).

Induction times at baseline ranged from 2.18 ± 0.03 to 19.45 ± 0.05 h and were static over time for only 2 products (one high oleic, refined safflower oil, and one flaxseed oil specifying cold storage and past the “best by” date by the 12‐month time point). The remainder of the products had shorter induction times by 6 months (10/14 products, 8 of which were significantly shorter again at 12 months) or 12 months (2/14 products). There are no regulatory or otherwise generally accepted thresholds for induction values. Usually, longer induction times correspond to higher oil stablity [24].

Principal component analysis is a multivariate technique for visualizing patterns of relationships among related data; it retains most of the variation in the data but allows for assessment of sample groupings based on similarities [25]. The principal component analysis performed on the 12‐month data generated a few overarching observations (Figure 1). There was an association between oils with high PUFA and saturated fatty acid content with shorter induction time, and between oils with high MUFA and longer induction time. Oils with a higher LA:ALA ratio also had higher peroxide and FFA values. Figure 1 shows one sunflower oil and one safflower oil that do not cluster with the other oils of this type, and these are the products with high LA claims. Other than those exceptions, oils of the same type tended to cluster together.

FIGURE 1.

Principal component analysis biplot of fatty acid composition and oxidative stability in 14 selected edible oils at 12 months of storage. Black dots: Specific oil samples (active observations); black vectors: The magnitude and direction of each variable's influence on the oil samples (active variables; monounsaturated fatty acids, induction time, omega‐6/omega‐3, free fatty acidity, peroxide value, polyunsaturated fatty acids, saturated fatty acids). Longer vectors imply stronger associations, and the angle between vectors reflects correlations.

4. Discussion

We aimed to assess selected edible oils commonly used in recipes for home‐prepared pet foods. Many recipes for home‐prepared pet diets rely on specific fat sources to deliver adequate amounts of essential fatty acids, including LA, the essential omega‐6 fatty acid for dogs and cats. However, sunflower and safflower oils, traditionally high in LA, have shifted to variations that are richer in oleic acid to allow for higher heating without impacting quality [3, 4]. Some formulators may use these oils in amounts that presume high LA concentrations, although commercial availability of such products is very limited. In addition, because nutritionists may limit the amount of vegetable oil in home‐prepared pet recipes to leverage more palatable components or to achieve overall fat restriction, even minor divergence from the expected composition could influence nutritional balance. Pet owners are at risk of using oils that do not provide appropriate amounts of fatty acids if they do not receive guidance regarding the correct product to use. Another potential issue is the possibility of fraud by dilution with other oil types, and this issue has been well described for olive oil and avocado oil. Whether it is an important problem for the oil types assessed in our study is unknown, but detection methods have been investigated for several oils of economic interest, including walnut oil and flaxseed oil [26, 27].

The products highest in LA were all corn and walnut oils as well as one of three safflower oils, and all samples tested exceeded the respective database value. Edible oil choices for home‐prepared pet diets are influenced by negative public perceptions, persuasive marketing, or presumed health impacts. Consumer selections often are influenced by the idea that certain edible oil products are not desirable or healthful. In addition, marketing terms such as organic or pure may impact consumer acceptance. Flax, sunflower, and safflower oil products were among the most expensive in our study, whereas corn and canola oils were the least expensive, but reliably matched the USDA entries.

Safflower oil products were variable in LA content, with one product falling below the USDA database value and another markedly exceeding it. Likewise, sunflower oils were highly variable in LA, and should not be considered a reliable source of LA. Only one sunflower oil tested in our study exceeded the FNDDS entry for LA and, although it was not specifically labeled as “high linoleic”, it did specify 9 g of LA per serving. Availability on the market is also a practical challenge. Few options with high LA claims were available, and the FNDDS entry for sunflower oil does not match most commercial products. In addition, one sunflower oil product that failed to meet the USDA database value also had the highest discrepancy between the label claim for PUFA content and the analysis (44%). Both formulators and consumers should have assurance that they are recommending and purchasing a product that provides a defined and adequate concentration of fatty acids, especially the essential nutrient LA. Given that three of the six total safflower and sunflower oils evaluated here did not match the USDA entry values for LA and had label claim discrepancies, these cannot be confidently recommended as a source of essential fatty acids in home‐prepared diet recipes.

Overall, label claims for fatty acid content and stated marketing terms were often inaccurate and possibly confusing. Nine of the 12 products assessed here had at least minor discrepancies between content claims and analyzed concentrations. In addition, some marketing claims regarding chemical composition or nutritional value are meaningless. For example, there is no regulatory constraint concerning oxidation and quality parameters on the use of the terms “refined” or “pure” despite the Codex definition for the former. Similarly, there is no regulatory definition for “cold pressed” in the United States although European Union rules are limited to certain temperature guidelines; however, “expeller pressed” means refined. One product in our study used the terms “cold processed” and “low temperature pressed” instead. In addition, one product claimed to be both “pure and unrefined”, which are terms with opposite meanings.

Most products were acceptably stable over the storage period, with an apparent benefit to cold storage which attenuates PUFA oxidation, as demonstrated by a shorter induction time in high‐PUFA oils. Oxidation of PUFA impacts not just palatability but also nutritional value. However, the results of quality assessments were not entirely predictable based on fatty acid content and saturation.

5. Limitations and Conclusions

This evaluation included a limited range of types and brands of edible vegetable oils and evaluated stability and quality using few parameters. In addition, our storage conditions were likely superior to what the products would be subjected to in the home environment. For example, oil products were kept at very stable temperatures with minimal light exposure and were not opened daily, which minimized oxygen exposure. Handling of edible oils by consumers at home is likely to be highly variable and may not always be consistent with best practices or manufacturer guidance. These factors were not explored in our study and should be characterized in the future.

To help ensure stability and minimize negative impacts on the overall nutritional value of the pet's diet, edible oils should be used within the expiry date and not exposed to excessive air and light. We recommend storing edible oils in refrigeration regardless of label instructions to help ensure stability over time. Oils used to supply essential fatty acids in home‐prepared pet foods should be selected carefully by a qualified and experienced recipe formulator, with preference for products that are less expensive, more reliable, and more stable.

Disclosure

Authors declare no off‐label use of antimicrobials.

Ethics Statement

Authors declare no institution animal care and use committee or other approval was needed. Authors declare human ethics approval was not needed.

Conflicts of Interest

The authors declare no conflicts of interest.