ISSUE FOCUS FEED & ADDITIVE MAGAZINE December 2024 27 ity from plant- and animal-derived food diets. Generally, animal-based ingredients are rich in selenium, whereas selenium levels in raw materials from vegetable origin are low. This can be explained, as selenium is not essential for plants. The selenium level in plant-derived ingredients depends on the selenium level of soil where the plant was grown, and can be very low and is highly variable between batches. Additionally, the bioavailability of trace elements from plant-based raw materials is often lower3. In contrast to plants, selenium is essential for animals, and meat-derived ingredients always contain a minimum amount of selenium. The selenium content varies depending on the part of the animal, with organs; such as the liver and kidneys containing higher levels compared to skeletal muscle tissue. Additionally, the animal’s origin impacts the selenium concentration, as fish-based ingredients usually contain higher amounts of selenium compared to products derived from land-based animals3. Pet food products containing more plant-based ingredients require additional selenium supplementation to meet the daily requirements of the animal and prevent selenium deficiency. Conversely, pet diets that are mostly based on organ-based or fish derived raw materials can fulfill the daily requirements, or even exceed the maximum levels, without additional selenium supplementation. The wide variation of selenium in raw materials makes it complicated to stay between minimum and maximum levels. But what are exactly the boundaries within which a pet nutritionist must adhere? WHAT ABOUT SELENIUM REQUIREMENTS The FEDIAF (2024) provides the minimum recommendations for selenium in growing and adult dogs and cats (Figure 2). In adults, the FEDIAF recommends nutrient levels based on the activity level of the animal. Less active animals have lower maintenance energy requirements (MER), and consequently a lower daily food intake. In order to meet the daily requirements, the selenium content in food for less active animals is higher. Although FEDIAF don’t specifically provide requirements for overweight animals, it can be seen that the MER for overweight dogs and cats is even below 95 kcal/ kg0.75 and 75 kcal/kg0.67 respectively. While weight loss diets often have a lower energy density, the daily amount of food provided to these animals is still less compared to normal sized pets. To reach the minimum daily recommendation, the level of selenium in a diet for overweight pets will become very A Total selenium (µg/L) GPX activity (µg/L) B 150 100 50 0 500 400 300 200 100 0 2.5 0 33.6 40.0 a a b b b b a a WD Flex VG VN WD Flex VG VN Figure 1. In a nutritional evaluation study, the selenium biomarkers in serum of people without meat in their diet are substantially lower, and relatively frequent below the limit of 50 µg/L (Klein, et al., 2023). (WD = omnivores; Flex = flexitarians; VG = vegetarians; VN = vegans)
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