# Comparison of Key Nutrient Content of Commercial Puppy Foods with Canine Dietary Requirements
## 1 Introduction
Throughout life, unsaturated fatty acids (UFAs) are present in cell membranes, influencing their flexibility. The higher their concentration, the more flexible the membrane becomes. However, increased amounts of saturated fatty  
Figure 1: Conversion of \(n-3\) fatty acids into LC–PUFAs, EPA and DHA, from their precursors based on [15; 16]. acids (SFAs) lead to the opposite effect, causing cell walls to become more compact [21]. Consuming DHA can have beneficial effects on the immune system during its development. This is particularly relevant for puppies that do not receive breast milk. DHA is believed to possess anti-inflammatory properties by reducing inflammation markers and increasing the number of phagocytes, albeit with decreased activity, as per one perspective [22]. During early growth stages, puppies mainly receive nutrients from their mother's milk, which contains these fatty acids [23]. Milk replacers can be used if necessary. However, some of them may lack or have a very low content of EPA and DHA, which are essential for this stage of life [24]. After transitioning to commercial food, puppies mainly rely on it for their LC-PUFA needs. According to the available literature, these LC-UFAs, including DHA and EPA, have been found to have beneficial effects on various systems, such as the nervous, immune, reproductive and digestive systems, as presented in Figure 2[19; 25; 26; 27; 28; 29; 30; 31; 32; 33; 34; 35; 36; 37; 38]. Although important, the amount of these fatty acids is not required to be declared on the label by manufacturers of complete feeds. Analytical constituents such as crude protein, crude fiber, crude fat, and crude ash are subject to mandatory declaration according to the EU regulation [3]. Other analytical constituents can be labeled on a voluntary basis. A complete pet food product labeled as such is, by law, balanced in such a way that it can serve as the animal's only source of nutrition without leading to nutrient deficiencies [3; 7]. Any unsuitable diet may have harmful health effects. The nutrition products industry is now facing the important challenge of identifying and reducing risks of unbalanced diets [53]. Therefore, it is necessary to evaluate the quality of the pet food, and a number of studies have been conducted to test dog food [54; 55; 56; 57]. One major issue is the imbalance in the manufactured products, including the lack of compliance of the composition with the FEDIAF nutritional guidelines [58]. The FEDIAF nutritional guidelines provide MRLs and maximum limits for nutrients. The levels given in the FEDIAF guide reflect the amounts of essential nutrients in commercial pet foods that are required to ensure sufficient and safe nutrition in healthy dogs when consumed over time. Minimum recommended levels include a safety margin to prevent deficiencies due to animal variations and nutrient interactions. For commercial dog and cat foods, it is recommended that the nutrient levels are at or above the levels listed in the tables and do not exceed the nutritional or legal maximum [7]. It is important that along with the amounts of protein and fat, commercial dog foods must provide enough essential amino acids and fatty acids. [PERSON] et al. [59] reported that 60% of commercial dry adult dog foods failed to meet at least one of the FEDIAF nutritional guidelines. [PERSON] et al. 's [60] study that aimed  
Figure 2: Potential effects of long-chain polyunsaturated fatty acids on various systems in growing and adult dogs based on [20; 32; 36; 39; 50; 51; 52]. to determine the elemental content of commercial adult dog foods found that all analyzed foods provided levels of macro- and micronutrients exceeding the recommended daily intake. Currently, it is difficult to choose the right food for puppies, because manufacturers usually do not declare the fatty acid content of a given food on the label. Furthermore, there is a lack of studies on puppies' food quality, especially when it comes to the nutritional adequacy of fatty acids.