Meal and Crumbles
Fine particle or meal type feeds for small fish are usually prepared by pelleting the ingredient mixure and subsequently reducing the size of the pellets by crumbling or grinding. Initial grinding of the ingredients prior to pelleting to a very small particle size (≤ 0.5 mm) is important. Firm bonding of the pellet is necessary so that during regrinding, the pellet is reduced into homogeneous small particles and not disintegrated. The particles from the reground pellets are separated into various sizes by creening. If supplemental fat is included in the diet, ith should be added after pelleting or after screening. Some meal type dies are not pelleted. The disadvantage of this procedure is that the water-soluble nutrients, such as some of the vitamins, dissolve very quickly after the feed is put into the water. Loss of water-soluble nutrients due to leaching is high with small particle diets, whether prepelleted or not, and heavey fortification of water-soluble vitamins (two or three times the minimum requirements) is recommended. Fat-soluble vitamins should be added in a fat or oil carrier. The addition of fat to the surface of meal and crumble particles improves water stability, helps them to float, and reduces leaching of watersloluble nutrients.