The Extru-Technician, Summer 2017
Density Pellet density determines whether the feed oats on the surface of the water or sinks Some species will only eat feeds that oat Others prefer to feed on pellets as they descend while still others wait for feed to reach the oor of the pond or pen Of note several species are adaptable accepting oating feeds in some parts of the world while sinking feeds are used in others Not only does the bulk density need to be in the correct range but individual pellets need to have uniform density as well Moisture Good control over drying is critical not only to meet storage requirements but also for economic and formulation considerations Durability Feed needs to be durable enough to meet manufacturing and logistical challenges Challenges can include not only handling during the manufacturing process but also during transportation and storage It is important to understand the effect of durability on the digestive process In some cases durability can adversely affect digestibility 4 Summer 2017 Palatability Pellets need to have these physical characteristics to ensure acceptability Taste may affect performance as well In addition to all this feed must be uniform from pellet to pellet If 99 percent of the batch is perfect that leaves one percent that the animals may never eat Put another way for every 100 pounds of feed added to the water one pound is pure waste with little purpose other than to tax ltration systems and provide a medium for pathogens During manufacturing lack of consistency comes about in many ways These include improper machine settings that lead to variation throughout the batch or changing conditions at start up and shut down Even if the process is off spec for just a few moments the entire batch may be contaminated It is also important to understand extrusion equipment is only part of the process Size reduction grinding mixing dosing coating conveying and packaging equipment all have How processing affects nutrition Feed manufacturing can alter the digestibility of ingredients and change nutrient bioavailability The bene ts of cooking and extrusion include reducing pathogens and making it easier for small sh to access foods they otherwise would not be able to consume However there are drawbacks Heat grinding and post extrusion drying can damage amino acids vitamins and carotenoids the naturally occurring pigments that give sh their color Manufacturers can mitigate the drawbacks by Reducing heating and grinding to the minimum needed to form safe pathogen free and digestible feeds Adding heat sensitive ingredients to the aquafeed after extrusion and drying Good candidates include oils probiotics enzymes and certain micronutrients Manufacturers should ensure the pellets have a structure that allows these coatings to adhere throughout storage and transportation For example salmon feed manufacturers have developed exceptional control over pellet cell structures that combined with the use of vacuum infusion ensure diets will not leach oil Feed needs to be sized correctly and durable enough to meet manufacturing and logistical challenges A shs environment affects both nutritional needs and which feed characteristics to prioritize
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