ARTICLE 74 FEED & ADDITIVE MAGAZINE October 2023 Therefore, it is necessary to optimize the extrusion temperature and pressure according to the ingredient. In addition to that, other nutrients in the ingredients also have an important role in the degree of gelatinization. It was also reported that high lipid content in the diet acted as a lubricant and reduced the duration of gelatinization. However, a higher temperature processing might solve this issue, but it would also lead to a chance of increasing lipid oxidation like long-chain PUFA and vitamin C destruction in the diet. Thus, higher temperature gelatinization potentially reduces the nutritional quality of aquafeed with high lipid content. The inclusion of PG starch has a positive influence on the overall feed quality. The inclusion of PG tapioca starch at 10% increased the feed quality compared to native tapioca starch. INFLUENCE OF STARCH GELATINIZATION ON GROWTH AND DIGESTIVE EFFECTS Starch gelatinization generally increases with the degree of digestibility but the influence of growth on the aquatic animals is highly variable. In addition, growth enhancement will also depend upon several factors like species-specific differences, starch type, the ratio of gelatinized starch to native starch, etc. The ratio of pre-gelatinized starch to native starch has been considered a significant contributor. For instance, better growth was reported when the ratio of PG potato to native potato at 1:1 or 1:2 than individual ingredients in Onchorhynchus mykiss. The same effect was observed in Seabream and European seabass at a 1:1 ratio. Similarly, when it comes to starch type, many findings reported a contradictory effect on growth. For example, gelatinized wheat inhibits growth compared to other gelatinized starch sources due to limited influence on gelatinization in O. mykiss and Cyprinus carpio. Later some authors reported its efficiency in increased digestibility in spite of its above adverse effects. But in the case of pre-gelatinized corn-fed seabream, native starch showed poor growth compared to PG corn starch. IMPACT OF STARCH GELATINIZATION ON ENZYMES ACTIVITY The study on the effects of starch gelatinization in enzyme modulation is limited. It was reported that amylase activity occurs when the complex starch source is used as an ingredient and required to metabolize easily digestible gelatinized starch. For example, PG corn starch has increased amylase activity compared to PG wheat or native wheat starch. The reason might be due to the presence of easily digestible or low amylose content in the ingredient. Similarly, trypsin activity was increased in Clarias gariepinus when fed with PG tapioca starch. In addition, protein sparing effect was observed with the decreased protease enzyme activity and increased amylase activity when fed with PG corn flour in Labeo rohita. This effect was detected by the enhanced activity of enzymes (aspartate and alanine aminotransferase) responsible for gluconeogenesis and glycolysis. IMPACT OF STARCH GELATINIZATION ON WATER QUALITY The fish waste production either as ammonia or feces is correlated with the amount of feed given and its utilization. There are indications that dietary PG starches can potentially minimize water quality deterioration due to gelatinized starches being better digested and in rare cases, reduce feed intake. It has been observed that fecal production was reduced by PG corn starch as a result of better digestibility of
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