In 2020, over half of the new canine diet consultation requests for The University of Georgia’s Clinical Nutrition Service were for a homemade diet formulation (JM Parr, DVM, College of Veterinary Medicine, University of Georgia, unpublished data, 2020). As dog owners become more interested in pet nutrition, they may choose to prepare a homemade diet. Common reasons for owners to turn to homemade diets include their desire for increased control over their dogs’ diet and the ingredients, mistrust of commercial pet food companies, belief that their dog dislikes commercial diets, and desire for increased bonding with their dog.1–4 Many times, homemade diets are simply the preferred option for owners. Homemade diets may also be used to nutritionally manage a variety of diseases if a commercial therapeutic diet is not available (eg, back-ordered diets) or does not meet the pet’s nutritional needs (eg, comorbidities, texture/aroma preferences).
To support the physiologic needs of healthy dogs, a cooked homemade diet should be formulated based on annual Association of American Feed Control Officials (AAFCO) and/or National Research Council (NRC) recommendations.2 When 200 homemade canine recipes were evaluated using computer-based and laboratory analysis, few recipes met NRC or AAFCO recommendations for canine adult maintenance,5 demonstrating the need for recipes to be acquired from trained formulators.3 Furthermore, when nutritional adequacy was evaluated in 27 adult dogs and 8 growing dogs consuming homemade diets, diets were found to be below AAFCO recommendations for multiple micronutrients.6 It is important when formulating homemade diets to combat the potential for nutritional deficiencies and toxicities through ongoing veterinary guidance and expertise with formulation software.3 Specifically, the authors recommend that homemade diet recipes should be formulated by either a Board-Certified Veterinary Nutritionist or a PhD nutritionist with advanced training in canine nutrition. Nutritionists typically formulate a diet using dog-specific multivitamin and multimineral supplements.2,3
Even if a homemade diet is formulated to be complete and balanced, it is crucial that the diet is prepared accurately to ensure that all nutrient requirements are met. Unbalanced homemade diets often result in vitamin and mineral deficiencies, leading to disease.7–9 For example, Tal et al7 documented that dietary calcium and vitamin D deficiencies can lead to nutritional secondary hyperparathyroidism and rickets in a growing puppy. It is common practice for North American Board-Certified Veterinary Nutritionists to prepare homemade diet recipes using weight measurements based on the United States Department of Agriculture’s national nutrient database known as FoodData Central (available at: https://fdc.nal.usda.gov/). This database uses food weight to determine nutrient content. Partridge et al10 suggested that using nutrient databases based on food weight may not provide accurate estimates of nutrient intake when volumetric measurements are used.
Most dog owners that feed dry commercial food use a measuring cup or food scoop.11 As such, owners may continue to use volumetric measurements when cooking a homemade diet for their dog due to ease and familiarity. Prior research12 has demonstrated that repeatedly measuring dry dog food with measuring cups results in significant inaccuracy. Significant over- and underestimation of dry dog food also occurs with measuring devices such as dry food measuring cups, graduated liquid measuring cups, and commercial food scoops.13 Thus, measuring ingredients using volumetric devices may be inaccurate, resulting in incomplete and/or unbalanced diets. No studies have determined the comparative accuracy and precision of volumetric versus weight-based measuring devices when preparing a cooked homemade diet. The purpose of this study was to determine the accuracy and precision of preparing cooked homemade diets for dogs by measuring ingredients by either volume (measuring cups and spoons) or weight (digital gram scale with a syringe for measuring oil only). It was hypothesized that measuring ingredients by weight would result in a diet that more precisely and accurately represented the expected nutrient profile.
Materials and Methods
Study procedure
Between June 2021 and July 2021, 21 members of the University of Georgia College of Veterinary Medicine community were recruited to participate in the present study by preparing a balanced homemade adult (maintenance) dog diet (Table 1). Participants were randomly assigned to prepare the diet either with measuring cups and measuring spoons (using what participants had available at home) or with a digital gram scale (calibrated scales were provided) and 20-mL syringe (for measuring oil only). Participants completed 2 repetitions of the diet preparation. Individuals who had fed a homemade diet to their dog in the past 12 months were excluded to ensure the study population represented owners who were less familiar with homemade diet preparation.
Cooked homemade diet recipes for dogs utilizing weight and volume measurements.
| Measurement | ||
|---|---|---|
| Ingredient | Weight4 | Volume4 |
| Cooked, boneless, skinless chicken thighs1 | 202 g | 1 and 1/3 cup2 |
| Cooked, long grain, white rice | 494 g | 3 cups |
| Cooked cauliflower3 | 78 g | 5/8 cup |
| Cooked broccoli3 | 49 g | 3/8 cup |
| Shredded raw carrots | 42 g | 3/8 cup |
| Canola oil | 16.5 mL | 5 and 1/4 teaspoon |
| BalanceIT canine supplement | 13 g | 5 and 1/4 teaspoon |
Bake chicken until an internal temperature of 165 °F has been reached (approximately 18 to 20 minutes at 450 °F). Do not add any seasoning or oil.
Estimated based on weighing 7 ounces of cooked chicken 10 times using a digital gram scale, placing the chicken in a measuring cup, and averaging the volume.
Add frozen vegetables to a microwave safe bowl, add a small amount of water, and cook for 4 to 5 minutes on high. Strain water once heated.
400 mL of water was added to each individual diet sample for homogenization prior to analysis.
Participants were given 2 pages of homemade diet instructions (Supplementary Appendix S1). The instructions mimicked recipes given to new clients preparing homemade diets at the University of Georgia College of Veterinary Medicine. The homemade diet was formulated by a Board-Certified Veterinary Nutritionist (JMP) to be complete and balanced for an adult dog based on AAFCO guidelines. Online formulation software (BalanceIT; available at: https://secure.balanceit.com/ez/index.php?rotator=NewEz) was utilized for the formulation. Participants were instructed to buy ingredients at a local grocery store. Then, participants were to prepare the diet in their own kitchen. Participants were provided with a small bag of a canine vitamin and mineral supplement (BalanceIT) and any necessary resources (eg, digital gram scale and 20 mL syringe) that they did not already have at home. Participants prepared the diet twice using the same instructions. The second diet was to be prepared 5 to 10 days after the first. Participants stored the diet sample at 4°C until submission, which was up to 3 days after preparing the recipe. The submitted diet samples were homogenized using a kitchen blender which required the addition of 400 mL of water (included in moisture analysis). Samples were frozen at –20°C for storage before being sent for analysis.
Laboratory analysis
The 42 diet samples were shipped on ice overnight to an ISO 17025 and National Environmental Laboratory Accreditation Program-accredited laboratory (Midwest Laboratories) for analysis, which was completed within 1 week. The samples underwent a proximate analysis (moisture, crude protein, acid hydrolysis fat [also known as crude fat], crude fiber, and ash) with the following minerals analyzed: phosphorus, potassium, magnesium, calcium, sodium, iron, manganese, zinc, and copper.
For moisture, analysis was based on Association of Official Agricultural Chemists (AOAC) 930.15.14 Samples were homogenized, weighed, and then placed in a 135°C convection oven for 2 hours. Samples were cooled in a desiccator and then reweighed. Loss in weight was reported as percent moisture. Analysis of protein was based on AOAC 990.03.14 Samples were placed in a combustion instrument to determine the amount of nitrogen. Nitrogen values for each sample were multiplied by a factor of 6.25. These values are reported as the crude protein. Fat was analyzed using acid hydrolysis based on AOAC 954.02.14 Samples were treated with ethanol and hydrochloric acid for fat analysis. Separate treatments of ethyl ether and petroleum ether were used to extract fat. Ethers were collected in a preweighed beaker. Ethers from each sample were then evaporated and dried at 70°C to remove the remaining ether and moisture. Material remaining in the beaker for each sample are reported as crude fat. Fiber was analyzed based on American Oil Chemists’ Society Ba 6a-05.15 Samples were weighed and placed in a sealed membrane bag. Bags were placed in a container that treats samples with a variety of chemicals to dissolve the minerals, which then leach out of the bags. Samples were repeatedly washed and rinsed in the bags, and then the bags were dried and reweighed. The material that remained in each bag was reported as the crude fiber. Ash analysis was based on AOAC 942.05.14 Samples were weighed and then placed in a 600°C muffle furnace to evaporate moisture and burn off organic material. Samples were removed and the remaining material was reported as ash. Mineral analysis (phosphorus, potassium, magnesium, calcium, sodium, iron, manganese, copper, and zinc) was based on AOAC 985.01.14 Samples were first prepared using a wet ash procedure that requires mineral acids and heat. Analysis of samples involved inductively coupled plasma analysis, during which sample extracts were nebulized and introduced into high-temperature plasma. This energizes the electrons of the dissolved minerals. As the energized electrons of the minerals return to ground state, the energy is released as light. Emitted wavelengths and light intensities were used to identify and quantify the minerals in the sample.
Nitrogen-free extract (NFE) is a calculated value that estimates the total amount of carbohydrates in the diet by excluding ash, crude fat, crude protein, and crude fiber. Ash is the inorganic material that is left in the diet samples after the water and organic matter have been burned off. The ash content of the diet is representative of the total mineral content of the diet samples.16 Although crude fiber values were acquired for the diets, values were not compared to the expected total dietary fiber in the recipe. Crude fiber has been shown to be a poor indicator of fiber concentration and composition in canine diets and underrepresents the total dietary fiber.17
Metabolizable energy calculations
Metabolizable energy (ME) values for each sample were calculated according to the NRC predictive equations for metabolizable energy in dog food.18
Formulas were as follows:
NFE = 100 - (%moisture + %crude protein + %crude fat + %ash + %crude fiber)
Gross energy (GE)(kcal/g) = (5.7 X g crude protein) + (9.4 X g crude fat) + (4.1 X [g NFE + g crude fiber])
Percentage energy digestibility = 91.2 - (1.43 X % crude fiber in dry matter)
Digestible energy (DE)(kcal/g) = (GE X percentage energy digestibility/100)
ME (kcal/g) = DE - (1.04 X g protein).
Nutrient values for each diet sample were compared to the expected nutrient profile values of the BalanceIT diet formulation on an energy density basis (EDB) and a dry matter basis (DMB). Energy density values were calculated as the grams of nutrient per 1,000 kilocalories (kcal) of food. This is more accurate given that dogs require calories in proportion to balanced nutrients. On the other hand, a dry matter value excludes moisture and gives the percentage of nutrient in the diet, which is another common method for comparing pet foods, especially those with vastly different moisture contents (eg, canned vs dry foods).
Statistical analysis
All analyses were performed using standard software (SAS version 9.4; SAS Institute Inc). A significance threshold of .05 was used. Differences were calculated by subtracting expected values from measured values for each analyte on an EDB and DMB in appropriate units. Differences were averaged over both replicates before analysis with t tests. There was 1 participant with only 1 diet preparation included in the analysis due to suspected exclusion of vitamin and mineral supplements during 1 diet preparation. Analyses were performed for each analyte on an EDB (grams per 1,000 kcal as fed) and a DMB (%) separately.
Histograms and Q-Q plots of differences for each method confirmed the assumption of normality was reasonable for each analyte. F tests were used to compare precision (standard deviation of differences) between methods. Since there was significant inequality of variances between methods for several analytes, Welch’s t tests were used to compare accuracy (mean difference) between methods. When variances were equal, Welch’s t test P values were of minimal difference from Student’s t test P values.
Accuracy was determined by measuring the average difference of measured from expected. Precision was determined by comparing the difference in standard deviation between the 2 methods.
Results
Forty-two total diet samples were analyzed; one sample was deficient in nutrients (2.4% of samples). This diet sample was deficient in magnesium, calcium, manganese, copper, and zinc per the NRC recommended allowance for adult dogs for maintenance on an EDB and phosphorus, potassium, magnesium, calcium, sodium, manganese, copper, and zinc on a DMB. It was also deficient in potassium, magnesium, calcium, manganese, copper, and zinc per AAFCO recommendations for adult dogs for maintenance on a DMB and phosphorus, potassium, magnesium, calcium, manganese, copper, and zinc on an EDB. Because this diet had multiple deficiencies, it was suspected that this participant neglected to include the vitamin and mineral supplements in this diet sample. For this reason, this diet sample was excluded from data analysis. The other 41 diet samples met current AAFCO and NRC recommendations for adult dogs for maintenance (97.6% of samples). A total of 22 diet samples were prepared by weight measurement tools (ie, using digital gram scales and syringes for measuring oil only) and 19 diet samples were prepared by volume measurement tools (ie, using measuring cups and measuring spoons).
The macronutrients crude protein, crude fat, and NFE were determined for all diet samples. Diet samples that were prepared by weight measurement tools resulted in significantly more precise amounts of crude protein, crude fat, and NFE on both an EDB and a DMB compared to the diet samples prepared by volume measurement tools (Table 2).
Averaged differences between measured and expected for nutrients on an energy density basis and dry matter basis for volume (n = 10 participants; 19 diet samples) and for weight (11 participants, 22 diet samples).
| Energy density basis | Dry matter | |||||
|---|---|---|---|---|---|---|
| Analyte/Method | Mean ± SD | F test | Welch’s t test | Mean ± SD | F test | Welch’s t test |
| Crude protein | ||||||
| Volume | 10.46 ± 10.28 g/1,000 kcal | 0.052 | 0.796 | 1.98 ± 4.57% | 0.045 | 0.708 |
| Weight | 9.87 ± 5.52 g/1,000 kcal | 1.52 ± 2.41% | ||||
| Crude fat | ||||||
| Volume | 2.55 ± 4.37 g/1,000 kcal | 0.002 | 0.177 | −0.06 ± 2.15% | 0.002 | 0.178 |
| Weight | 0.17 ± 1.56 g/1,000 kcal | −1.21 ± 0.76% | ||||
| Nitrogen-free extract | ||||||
| Volume | −6.14 ± 2.11 g/1,000 kcal | 0.010 | 0.457 | −6.01 ± 5.59% | 0.053 | 0.296 |
| Weight | −5.42 ± 0.89 g/1,000 kcal | −3.84 ± 3.02% | ||||
| Crude Fiber | ||||||
| Volume | 3.29 ± 0.62 g/1,000 kcal | 0.073 | 0.531 | 1.37 ± 0.26% | 0.063 | 0.420 |
| Weight | 3.14 ± 0.36 g/1,000 kcal | 1.29 ± 0.14% | ||||
| Ash | ||||||
| Volume | 6.95 ± 0.70 g/1,000 kcal | 0.141 | 0.037 | 2.71 ± 0.19% | 0.013 | 0.014 |
| Weight | 5.89 ± 1.23 g/1,000 kcal | 2.24 ± 0.50% | ||||
| Phosphorus | ||||||
| Volume | 0.21 ± 0.19 g/1,000 kcal | 0.848 | 0.109 | 0.02 ± 0.07% | 0.778 | 0.055 |
| Weight | 0.05 ± 0.17 g/1,000 kcal | −0.05 ± 0.07% | ||||
| Potassium | ||||||
| Volume | 0.41 ± 0.46 g/1,000 kcal | 0.022 | 0.564 | 0.08 ± 0.18% | 0.025 | 0.433 |
| Weight | 0.23 ± 0.16 g/1,000 kcal | 0.00 ± 0.06% | ||||
| Magnesium | ||||||
| Volume | 0.05 ± 0.06 g/1,000 kcal | 0.197 | 0.792 | 0.01 ± 0.02% | 0.213 | 0.608 |
| Weight | 0.03 ± 0.02 g/1,000 kcal | 0.00 ± 0.01% | ||||
| Calcium | ||||||
| Volume | 0.45 ± 0.36 g/1,000 kcal | 0.898 | 0.101 | 0.11 ± 0.14% | 0.936 | 0.072 |
| Weight | 0.14 ± 0.34 g/1,000 kcal | −0.03 ± 0.14% | ||||
| Sodium | ||||||
| Volume | 0.02 ± 0.08 g/1,000 kcal | 0.799 | 0.554 | −0.01 ± 0.03% | 0.914 | 0.391 |
| Weight | −0.01 ± 0.05 g/1,000 kcal | −0.02 ± 0.02% | ||||
| Iron | ||||||
| Volume | 3.92 ± 4.03 mg/1,000 kcal | 0.446 | 0.020 | 5.40 ± 17.70 ppm | 0.673 | 0.016 |
| Weight | −1.16 ± 4.22 mg/1,000 kcal | −16.93 ± 17.12 ppm | ||||
| Manganese | ||||||
| Volume | 0.46 ± 0.65 mg/1,000 kcal | 0.578 | 0.415 | 0.36 ± 2.39 ppm | 0.797 | 0.333 |
| Weight | 0.20 ± 0.57 mg/1,000 kcal | −0.83 ± 2.32 ppm | ||||
| Copper | ||||||
| Volume | 0.99 ± 0.50 mg/1,000 kcal | 0.907 | 0.609 | 3.19 ± 2.00 ppm | 0.901 | 0.537 |
| Weight | 0.80 ± 0.41 mg/1,000 kcal | 2.31 ± 1.67 ppm | ||||
| Zinc | ||||||
| Volume | 7.06 ± 6.36 mg/1,000 kcal | 0.577 | 0.130 | 14.12 ± 24.88 ppm | 0.763 | 0.082 |
| Weight | 2.23 ± 4.54 mg/1,000 kcal | −7.22 ± 18.59 ppm | ||||
| Moisture | ||||||
| Volume | 8.41 ± 2.70 g/1,000 kcal | 0.078 | 0.740 | |||
| Weight | 7.79 ± 1.46 g/1,000 kcal | |||||
| Dry Matter | ||||||
| Volume | −8.41 ± 2.70 g/1,000 kcal | 0.069 | 0.740 | |||
| Weight | −7.79 ± 1.46 g/1,000 kcal | |||||
| Metabolizable energy | ||||||
| Volume | −0.41 ± 0.11 kcal/g | 0.128 | 0.838 | |||
| Weight | −0.39 ± 0.07 kcal/g | |||||
Differences were averaged over both replicates before analysis. The P values for the F test evaluated standard deviations between the preparation methods and indicate the precision of the methods. The P values for the Welch’s t test evaluated means and indicate the accuracy of the methods. P < .05 was considered significant.
For potassium, diet samples prepared by weight measurement tools resulted in significantly more precise amounts of potassium on both an EDB and a DMB (Table 2). The other macrominerals in the diet samples (phosphorus, magnesium, calcium, and sodium) did not differ significantly in accuracy or precision between the 2 different measurement tools.
On a DMB, volume measurement tools resulted in diet samples with more precise amounts of ash. However, diet samples that were prepared with weight measurement tools resulted in more accurate amounts of ash on both an EDB and a DMB (Table 2).
The amount of iron in the diet samples was more accurate when prepared with weight measurement tools on an EDB; however, on a DMB, volume measurement tools resulted in more accuracy (Table 2). Other microminerals (manganese, copper, and zinc) did not differ significantly in terms of accuracy or precision between the 2 different measurement tools.
Values for metabolizable energy were calculated for each diet sample. These energy values did not differ significantly based on the measurement method on an energy density basis (Table 2).
Discussion
The current study demonstrated that using digital gram scales results in greater accuracy and precision for diet samples in terms of macronutrients on both an EDB and DMB when compared to using measuring cups and measuring spoons. This finding supports the hypothesis that measuring ingredients by weight results in diet samples that more precisely and accurately represent the expected nutrient profile. Ultimately, accuracy is important for cooked homemade diets to ensure the diet matches the intended nutrient profile and energy density, whereas precision ensures that the cooked homemade diet will be the same each time it is made by the owner (ie, a consistent diet).
The finding that weight measurement tools resulted in significantly greater precision (ie, consistency) in terms of macronutrients also supports the authors’ current recommendations to have owners utilize digital gram scales when preparing cooked homemade diets for dogs. While the current study focused on adult maintenance diets for healthy dogs, precision is critical in terms of macronutrients when preparing diets for therapeutic purposes, especially when the amounts of specific macronutrients are critical for a patient (ie, crude fat for dogs with familial hyperlipidemias or lymphangiectasia; crude protein for dogs with hepatic encephalopathy or end-stage chronic kidney disease [CKD]). A short communication19 from 2014 analyzed 6 cooked homemade diet samples prepared by 6 different veterinary nurses. The recipe utilized was previously published for dogs with CKD.20 The communication’s author concluded, “Veterinarians should not have confidence in the use of homemade diets prepared by pet owners for the management of CKD in their dogs, or for any other clinical condition.”19 However, there were several challenges with the instructions provided, resulting in weighing raw meat with or without packaging, using both kitchen scales and butcher scales, and adding oil before or after cooking. These challenges likely impacted macronutrient precision. Additionally, it was unclear if digital or analog scales were used by the participants. Although this study utilized weight measurement tools to prepare diet samples, instruction details were not sufficient to result in consistent nutrient profiles. Therefore, cooked homemade diet recipe instructions must provide sufficient detail and even consider use of images and/or videos as visual aids to assist with consistent preparation.
According to the statistical analysis (n = 41), the amount of ash in the diet was significantly more accurate in diet samples prepared with weight measurement tools, suggesting that volume measurement tools may result in inaccurate amounts of minerals in homemade cooked diets. In the present study, these inaccuracies did not lead to deficiencies for adult dogs as compared to current AAFCO and NRC recommendations. However, certain life stages and disease states have more stringent dietary mineral recommendations. For example, growing puppies require diets with optimal calcium and phosphorus amounts that do not fall below minimums or exceed maximums to promote proper growth and development.7 Per the current AAFCO recommendations, calcium and phosphorus should also be supplied in an appropriate ratio ranging from 1.0 to 2.0 parts calcium to 1.0 parts phosphorus for growth and adult maintenance.21 Furthermore, nutritional management is considered a mainstay of canine CKD treatment based on prior research in spontaneous chronic renal failure in dogs.22 Based on the authors’ experience, dog owners may pursue a homemade cooked diet for several reasons, of which losing interest in commercial diets (including dry, canned, and/or fresh food diets) formulated for CKD is routinely noted. Typically, a diet formulated for end-stage CKD will have modified amounts of phosphorus along with other nutrient modifications that are beyond the scope of this paper.23,24 In the aforementioned short communication19 from 2014, phosphorus was the only micronutrient analyzed and revealed a range of 0.17% to 0.46% DMB and 0.88 to 2.42 grams/1,000 kcal EDB. This variation was likely compounded by vague supplement instructions, which were to “Add a low-phosphorus mineral and vitamin supplement.”20 Given it is crucial that the amount of each mineral is accurately maintained when cooked homemade diets are prepared, weight measurement tools should be utilized both when measuring vitamin/mineral supplements and other ingredients.
Certain results differed on an EDB versus a DMB for some nutrients. Iron values were more accurate in the diet samples prepared with volume measurement tools on a DMB, contradicting the results found on an EDB, where the amount of iron was more accurate when prepared with weight measurement tools. This discrepancy could be due to the relatively small number of diet samples tested and/or limitations of the standard mineral testing methods. Diet samples were compared on both a DMB and EDB, both of which are standard methods for comparison in the commercial pet food industry. DMB is useful when comparing 2 diets with vastly different moisture contents, such as extruded dry food (less than 20% moisture) versus canned food (more than 65% moisture) versus a cooked homemade diet (greater than 20% moisture). The diet samples used in this study all had similarly high moisture contents comparable to canned foods (74.5% to 84.2%), especially given the 400 mL of water added to each diet sample for homogenization. Because dogs are fed based on daily caloric requirements, the EDB can determine the amount of nutrient per calorie fed.25 Thus, EDB is more relevant when evaluating and comparing diets.25 Iron values were more accurate for weight measurement tools on an EDB, suggesting that weight measurement tools should be utilized to improve the accuracy of iron as fed to an individual dog based on daily caloric requirements.
The single diet sample that was excluded from the study due to multiple deficiencies exhibits how important vitamin and mineral supplements are during cooked homemade diet preparation. Out of 2 diet preparations, it was suspected that a single participant forgot to include the supplement in 1 preparation resulting in a diet that was deficient in 7 minerals on an EDB and 6 minerals on a DMB per AAFCO adult maintenance recommendations. The same diet was deficient in 5 minerals on an EDB and 8 minerals on a DMB per the NRC adult maintenance recommended allowances. Long term, mineral deficiencies may be difficult to diagnose until the later stages, as is often the case with chronic calcium deficiency, which can result in bone demineralization and overall bone mass loss, leading to the potential for spontaneous fractures.26 If dog owners continuously exclude the vitamin and mineral supplement when preparing their dog’s cooked homemade diet, these undesirable outcomes may occur over time. Future studies could estimate how often dog owners forget to include the vitamin and mineral supplement when preparing these diets repeatedly over long periods of time. Oliveira et al4 reported that in a 2-year period, 30.4% of owners admitted to modifying a homemade diet recipe, with 28.3% of owners omitting the vitamin and mineral supplement entirely. The outlier in the present study highlights the importance of a vitamin and mineral supplement, and as such, veterinarians should convey the importance of using the correct supplement in the correct amount every time the diet is prepared.
One major limitation of the present study was the small sample size. Another important limitation was that all participants were from the University of Georgia College of Veterinary Medicine community, including staff and students. This could have resulted in some bias toward individuals more knowledgeable about veterinary nutrition. Although the participants bought ingredients from a variety of grocery stores, they were all located in Athens, GA. It has been shown that ingredients produced in different regions of the world result in different nutrient profiles.27 Therefore, if the participants were recruited from different regions of the world, the diet samples may have had more variety. Participants were also aware that they were preparing the diets for a research study. It is likely that dog owners from the general population, unaware of study participation, would prepare diets with even more variability. It is also likely that variability would increase if owners prepared these diets over longer periods of time, as was seen in the 2014 study by Oliveira et al.4 Furthermore, due to cost constraints, only a complete proximate analysis with minerals was performed for each diet sample. Therefore, the analysis of the diets was limited to the nutrients that were able to be measured. Future studies could investigate even more nutrients in cooked homemade diets, such as essential vitamins, amino acids, fatty acids, and choline.
In the future, a similar study could be conducted that includes cooked homemade diets for cats. Because cats are typically smaller than dogs and therefore have lower daily caloric requirements, cooked homemade diet recipes for cats typically include smaller measurement portions, which could potentially introduce more error. Furthermore, there are limited studies evaluating feline homemade diets overall.
Studies are also warranted to determine pet owner’s accuracy and consistency when preparing these diets over long periods of time. As stated previously, diet drift occurred in a study over a little less than 2 years.4 Additionally, in a 2016 survey-based study,28 only 13% of respondents (4 out of 30) precisely adhered to the homemade diet recipe based on the nutritional history collected. Longer-term studies are warranted. Additional studies could also evaluate the best instructional methods for cooked homemade diet recipes, including written instructions, images, or videos. These studies could help Board-Certified Veterinary Nutritionists and pet owners further improve the accuracy, precision, and adherence of cooked homemade diets.
In conclusion, volume measurement tools such as measuring cups and measuring spoons may lead to inaccurate and imprecise measurements of nutrients in a homemade cooked diet. Weight measurement tools, like digital gram scales, offer a more accurate and precise method to prepare these diets. As a result, veterinarians should advocate for the use of weight measurement tools when educating pet owners about cooked homemade diet preparation. Furthermore, pet owners preparing these cooked homemade diets should be instructed on the use of digital gram scales to increase adherence.
Supplementary Materials
Supplementary materials are posted online at the journal website: avmajournals.avma.org
Acknowledgments
The authors thank Melanie R. Parham for her assistance with diet collection and processing, Lisa Reno for assistance with project logistics, and Dr. Deborah Keys for statistical support.
This research project was funded by a grant from the University of Georgia (UGA) Department of Small Animal Medicine and Surgery. Grace Boothby received funding for her summer position through Georgia Veterinary Scholars Program from Boehringer Ingelheim. Funding for Dr. Parr’s position at UGA was provided as a gift by Nestlé Purina PetCare.
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