Pet Food Evaluation and Quality Control

Pashu Sandesh, 23 Feb 2024

Maskare Rahul Mahavirprasad1*, Monika Karnani2, Sheela Choudhary3 and Manju4

1*M.V.Sc. Scholar, Department of Animal Nutrition, PGIVER, Jaipur 

2Assistant Professor, Department of Animal Nutrition, PGIVER, Jaipur 

3Professor and Head, Department of Animal Nutrition, PGIVER, Jaipur

4Assistant Professor, Department of Animal Nutrition, PGIVER, Jaipur 

Abstract: Pet food production has increased as a response to the increase in the population of dogs and cats in the world, where 50% of households own at least one dog and this indicates more responsible ownership in terms of feeding pets. Part of the process of making dry pet food involves a thermal process called extrusion, which is capable of eliminating the microbial load. However, extrusion can compromise nutritional quality to some extent by denaturing proteins, oxidizing lipids and reducing digestibility. The objective of this study was to evaluate the quality and safety of dry pet food and to assess the effect of the extrusion process on digestibility and the quality of proteins, amino acids and fatty acids. Pet food samples were collected before and after extrusion and were used to evaluate Good Manufacturing Practices (GMP), based on Central American Technical Regulation (RTCA). Feed safety was surveyed by analysing Escherichia coli, Listeria spp., Staphylococcus aureus, Salmonella spp., aerobic mesophilic microorganisms, yeast and fungi counts. The extrusion process effectively reduced pathogenic microorganisms and showed no effect on the digestibility of dog food, however, it could reduce the availability of some nutrients (e.g., amino acids, fatty acids). Finally, it can be confirmed that the correct implementation of GMP allows feed manufacturers to deliver a product of optimum texture, smell, nutritional composition and safety.


Keywords: Quality assurance; Pet food; good manufacturing practices


Introduction: People's lives are significantly impacted by their dogs, especially the mental and physical health of their owners, who now view their animals as "family members." Appropriate nutrition is essential to satisfy the needs of pets effectively, ensuring their good health and long-term well-being. Commercial dry pet food has become a standard as pet owners feed their animals with more awareness of the meal's quality. Health, safety and quality standards to assure feed and food safety are getting more and more strict because of the intimate interaction between animal feed and food intended for human consumption. This relationship is built on a comprehensive production system that goes by the phrase "from farm to fork."Good manufacturing practices” (GMP) serve as the cornerstone in the food sector to mitigate the risk of physical, chemical, and biological hazards emerging at any stage of the food production process. Temperatures between 80-150C are used during the conditioning and extrusion phases of making dry pet food. These temperatures offer the benefit of decreasing waste, extending product shelf life and enhancing carbohydrate digestion. On the other hand vitamin activity, lipid oxidative degradation and amino acid availability could all decrease during extrusion. Therefore, it's important to maintain standardized and ideal processing conditions to reduce negative effects on the finished product. Salmonella spp. and other harmful germs are also eliminated from the food by the temperatures attained during the extrusion process. Conversely, food drying and cooling procedures lower the temperature to roughly 20C and limit the moisture content to a maximum of 13g/100g respectively, giving the finished product the best storage conditions and preventing bacterial and fungal growth. Dry pet meals are a cost-effective substitute for wet food since they are simple for pet owners to store and handle and because they are a balanced diet, they should meet all of the animal's nutritional requirements in a few manageable amounts. Therefore, it is essential to assess the market value of pet food as well as the overall health of the food system. Here, we present the results of multiple tests to evaluate the quality of dog, cat and puppy food.



1. Analyzed Samples 

Sampling was carried out at different stages of the process (one area after the mixing process and another at the end of the processing line) within two pet food production establishments located in specific areas. A minimum of two samples of each production batch (i.e., four samples per batch— after mixing and two of the finished product) were sampled at least five times per establishment. Sampling was performed according to the procedure described in the Association of American Feed Control Officials (AAFCO) [1]. The number of samples was determined by a retrospective analysis and was proportional to the volume of the different types of pet foods found in the market (i.e., dog > puppy > cat food). For example, dry extruded dog food (n = 15), dry extruded puppy food (n = 10), and dry extruded cat food (n=5).  Samples consisted of commercially available presentations of pet foods (i.e., finished product samples). All samples were quartered and sieved to 1 mm particle size following AOAC. The number of samples was determined based on a retrospective analysis of the data surveillance program. The analysis considered the most common feedstuffs used in that particular area, target growth stage, import and export regulations, contamination risk, the productivity of the pet food industry and the risk for human and animal health associated with each food type. For example, some analyses were included during the retrospective analysis of puppy food that were not included in the adult food analyses, as young dogs may be more susceptible to certain nutrient deficiencies(Cortes-Herrera,2019).


2. Reagents and Quality Control Materials

For quality control purposes, proficiency test samples (dog food) and (dry cat food)from the AAFCO’s check sample program were used for all chemical/nutritional assays, including fatty acid, amino acid profiling, and water activity. Sample (dog food) from the quarterly mineral scheme was used as quality control for calcium, phosphorus and heavy metal analysis.


3. Evaluation of Good Manufacturing Practices (GMP) 

A GMP diagnosis was made based on the Central American Technical Regulation (RTCA). Quality begins with the selection of raw materials, GMP dictates that manufacturers must source ingredients from reputable suppliers who meet stringent quality standards. Through testing and evaluation of raw materials help ensure their safety and nutritional value. This is particularly crucial as pet food formulations often require a balance of various nutrients to meet specific dietary needs. Critical steps in GMP are proper handling and storage of raw materials. Facilities must be designed and maintained to prevent contamination and deterioration.


4. Food Safety: Heavy Metal Analysis 

The heavy metal analysis was performed using a methodology described by Granados-Chinchilla and coworkers [3]. Briefly, 300 mg of the sample was placed into the digestion vessel and mixed with 10 ml of HNO3. The mixture was microwave-digested using a 3-step temperature program. 

Step 1: temperature- 175C, pressure-30 bar, heating time-5min, hold time-5min, power-70%

Step 2: temperature-230C, pressure-30 bar, heating time-1min, hold time-10min, power- 90%

Step 3: temperature-50C, pressure-25 bar, heating time-1min, hold time-10min, power-0%. 

Limit of detection and quantification for arsenic (1.00 and 3.03µg/kg), cadmium (0.01 and 0.03µg/kg), mercury (0.02 and 0.06µg/kg) and lead(0.60 and 1.82 µg/kg) in dog food.


5. Nutritional Quality: Proximate Analysis 

Dry matter, crude protein, crude fibre and ash as well as calcium, phosphorus and pepsin digestibility of animal protein assays, were performed to assess the nutritional quality of the pet food.  Ether extract and water activity (aw) were calculated in extruded pet foods by acid hydrolysis.


6. Nutritional Quality: Fatty Acid Profiling 

A 250 g pet food sample was milled and sieved to 1 mm using an ultracentrifuge mill. After that,1 g of each feed sample was placed in a 50 ml glass beaker, where 5 ml of diethyl ether was added and mixed using an ultrasonic shaker for 5 minutes. Afterwards, a 200 µl aliquot was transferred to a GC 2 ml vial. Then, 800 µl of diethyl ether and 1000 µl of a previously prepared, 0.25 g/100 ml TMHA solution in methanol were added to the same vial. An aliquot of 2 µl of the resulting mixture was injected into the GC system. Qualitative analyses of the volatile compounds were carried out using a gas chromatograph. The carrier gas was helium at a constant flow rate of 0.3 ml/min. The oven temperature was kept at 50oC for 0.34 min and increased to 200 oC at a rate of 72.51 oC/min. The temperature was kept at 200oC constant for 0.17 min, increased to 230 oC at a rate of 8.7 oC/min and remained constant for 7.9 min for a total run time of 13.93 min. The split ratio was adjusted at 30:1. The injector, transfer line, ion source and quadrupole temperatures were set at 250, 250, 230 and 150 oC respectively. The mass range and the electron energy were set at 50-450 m/z and 70 eV respectively. Constituents were identified by matching their spectra with those in NIST library 14. Only hits with a match factor above 80% were considered. FAME mixtures (A mixture of 25 fatty acid methyl esters) were used as quality control comparing retention times and mass spectra with those found in the analyzed samples. Compounds used to check mass tuning included tetradecanoic (6.16 min; [M+] 227.6 m/z), pentadecanoic (6.72 min; [M+] 243.4 m/z), hexadecenoic (7.58 min; [M+] 256.3 m/z), octadecanoic (9.70 min; [M+] 285.5 m/z), cis-13-octadecanoic (10.21min; [M+] 285.7 m/z) acids. Enanthic acid was used as an internal standard and was concurrently monitored by simultaneous ion monitoring (SIM) mode with a total dwell time of 100 ms and cycles of 8.3 Hz. For compounds with no standard, identification should be considered tentative. 


7. Nutritional Quality: Amino Acid Profiling  

Feed samples were sieved to 1 mm, and 200 ± 1 mg subsamples were used for digestion. The sample was transferred into a 40 ml glass vial, mixed with 2 ml water (to achieve dispersion), and 6 ml of an HCl 10.6 mol/L aqueous solution. Immediately, the vial was capped with a septum and nitrogen was bubbled for 1 min into the solution through a needle. The resulting mixture was heated adiabatically for 23 h at 110 oC. The resulting hydrolysate was filtered by gravity through a grade 4 qualitative Whatman filter paper. Then, 130 µl of a borate buffer (50 mmol/L, pH = 10), 10 µl sample digest, 20 µl NaOH (3.6 mol/L), 10 µl OPA freshly prepared solution (10 mg o-phtalaldehyde is dissolved in 500 µl chromatographic grade ethanol and made up to volume with borate buffer in a 10 ml volumetric flask), 10 µl FMOC (10mg 9- fluorenyl methoxycarbonyl chloride is dissolved in 500 µl chromatographic grade acetonitrile and made up in borate buffer in a 10 mL volumetric flask), 320 µL ultrapure water were 5 of 25 sequentially mixed in an HPLC ready-to-inject vial. One microliter of the resulting mixture was injected into the LC system. The solvent system consisted of a 40 mol/L NaH2PO4 buffer adjusted at 7.8 pH (98% pure, solvent A) and acetonitrile, methanol and water (45:45:10, solvent B). Gradient mode was as follows: 0% B at 0 min, 0%B at 1.9 min, 57% B at 18.1 min, 100% B at 18.6 min, 100% B at 22.3 min, 0% B at 23.2 min, and 0% B at 26 min. Chromatographic separations were performed using an Agilent Technologies LC system equipped with a resolution column, an infinity quaternary pump, a column compartment, an automatic liquid sampler module and a fluorescence detector. A detection system was set at 340 nm (excitation) and 450 nm (emission) for all amino acids except proline for which 266 and 305 nm wavelengths were used, respectively. Ultrapure water was obtained using an A10 Milli-Q Advantage system and an Elix 35 system. The identity of each amino acid was assessed and each compound quantified an amino acid in 0.1 mol/L.


  1. Palatability Evaluation

Palatability is the perception derived at the time food is consumed and accounts for the flavour and the animal’s perception of the appearance, temperature, size, texture, consistency and perhaps prior experiences (Kitchell, 1978). There are two different methods of palatability evaluation


A. The Single Bowl Test

In the single-bowl test, food is weighed and offered to the animal. The amount of food consumed is based on the difference between the first meal offered and the leftovers after a predetermined time. This is repeated over several days, usually five days or more, and can be observed under standard feeding conditions alone or for numerous feedings each day. Frequently, the meal is changed to something else, and the process is repeated. In this instance, intake in a switchback design can be compared between the phases. It is possible to utilize several dogs or cats for experiments, balancing them over time to remove any effects from the surroundings. The findings show whether the animal rejects a new diet when given no other option or whether it consumes more or less of one food throughout several periods. This test has the advantage of closely simulating the home environment, where the animal is fed a single diet and has no choice but to comply. It works well for recognizing goods that have an off flavour, smell, or texture and/or may give rise to certain digestive issues if consumed over an extended length of time. This test yields no information about preference, level of like, or any other hedonic feature of the food; instead, it measures or infers "acceptance." Additionally, dogs and cats adapt to new or different diets in various ways, and this technique does not account for these changes based on species.


B. The Two bowl Test

With this approach, the animal is given two meals at the same time, each in its dish. There is a choice, in contrast to the single bowl test. The food bowls are simultaneously placed in front of the animal for consumption after allowing the animal to smell the food. The technician will keep track of which of the two foods was nibbled first and which was approached first.  This “first bite” is commonly assumed to be related to the aromatic characteristics of the food. The animal is given the bowls for a predetermined amount of time, usually 15 to 30 minutes, or until one of the bowls is finished. Each bowl of food should contain enough food to meet the animals' daily caloric needs. After an overnight fast, the test is given in the morning. To find out which bowl was devoured more than the other, the total amount of food in each of the two bowls is measured. As a result, preferences for Food A, Food B, neither, or a combination of the two could emerge. It is best if the animals can show that each bowl was tried by sniffing and even choosing from it.


Quality control

Pet food quality control procedures are supervised and enforced by several organizations. These groups create rules, define benchmarks, carry out audits, and guarantee that safety and quality standards are met.

1. Association of American Feed Control Officials (AAFCO):

It is an organization of volunteer state, federal, and international entities that offers a platform for the creation and execution of standardized rules about animal feed. States can use the model regulations and ingredient definitions established by AAFCO as a guide for creating their regulations.


2. Food Safety and Standard Authority of India (FSSAI):

The FSSAI is the primary regulatory body in India responsible for overseeing the safety and quality of food products, including pet food. FSSAI sets standards for pet food ingredients, labelling, and packaging, ensuring that pet food manufacturers comply with these standards.


3. Bureau of Indian Standards (BIS):

In India, the BIS is a national standards organization that might be involved in establishing guidelines for pet food. If appropriate, its standards include recommendations for many areas of pet food production, such as ingredient safety and quality.



4. Food and Drug Administration (FDA):

The FDA is a federal organization tasked with safeguarding and advancing public health, which includes controlling pet food. Food safety regulations in India are implemented and enforced at the state level by inpidual FDAs or similar authorities in each state. Within their jurisdiction, state FDAs have the authority to audit and inspect pet food production facilities.



Pet food quality assurance and evaluation are essential to guaranteeing the general health, safety, and welfare of companion animals. From sourcing ingredients to packaging, all of the extensive procedures used in the manufacture of pet food are created to adhere to strict guidelines and standards. Pet food's nutritional purity is guaranteed by strict quality control procedures. The provision of a full and well-balanced meal for pets is guaranteed by precise formulation, thorough ingredient analysis and respect for nutritional guidelines. The safety of pet food is enhanced by ongoing inspection and testing for microbiological and chemical pollutants. Tight quality control procedures reduce dangers to pets by assisting in the identification and resolution of possible problems. Palatability for dogs and cats is the measure of intake of food that indicates acceptance or the measure of preference for one food over another.



1. Association of American Feed Control Officials (AAFCO). Feed Inspector’s Manual, 5th ed.; Association of American Feed Control Officials Inspection and Sampling Committee: Champaign, IL, USA, 2014; 220p

2. Cortés-Herrera, C.; Artavia, G.; Leiva, A.; Granados-Chinchilla, F. Liquid Chromatography Analysis of Common Nutritional Components, in Feed and Food. Foods 2019, 8, 1. [CrossRef]

3. Granados-Chinchilla, F.; Prado-Mena, S.; Mata-Arias, L. Inorganic contaminants and composition analysis of commercial feed grade mineral compounds available in Costa Rica. Int. J. Food Contam. 2015, 2, 8. [CrossRef]

4. Kitchell, R.L. Taste perception and discrimination by the dog. Adv. Vet. Sci. Comp. Med. 1978,22, 287–314. [PubMed]