Among the various quality indicators for feed, freshness undoubtedly stands as the primary golden standard—it directly determines the bioavailability and safety of nutrients. Freshness encompasses both the freshness of raw materials (such as the oxidation level of fishmeal and the peroxide value of fish oil) and the preservation state of the finished product. Deterioration in freshness can lead to vitamin inactivation, fatty acid rancidity, and toxin formation.
Key indicators that follow closely include:
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Effective Protein Content and Amino Acid Balance: The proportion of utilizable protein within crude protein and whether the ratios of essential amino acids like lysine and methionine align with koi growth requirements.
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Effectiveness of Functional Ingredients: For example, the phycocyanin content in spirulina and the isomer form of astaxanthin (natural left-handed isomer is superior to synthetic).
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Processing Technology and Stability: Extrusion technology affects starch gelatinization (preferably >85%) and pellet disintegration time (should not disintegrate after 2 hours of immersion in still water), as well as vitamin retention rates during high-temperature processing.
Other factors such as the stability of vitamin premixes, the chelated forms of trace elements, and the formulation of antioxidant systems (e.g., vitamin E, tea polyphenols) are also essential. Ultimately, high-quality feed should achieve comprehensive ecological benefits, including "high digestibility (>90%), low ammonia excretion, and minimal water pollution."
