Originally published in Aquafeed
In the autumn 2013 edition of Aquafeed, Dr. Nabil Said of Insta-Pro International discussed the new MS3000 Medium Shear Extruder for making high-quality, shaped, aquafeed pellets (see Aquafeed, autumn 2013, volume 5, issue 3, pages 41-45). In it, he described the market conditions that led to the development of a low cost, easy to operate, and rugged equipment solution for small to medium scale fish feed producers. Also mentioned is that the new MS3000 Medium Shear Extruder is based upon existing high shear extrusion technology.
Current market conditions in the aquafeed industry have renewed interest in using high shear, dry extrusion to recycle aquatic co-products for use in fish diets. This is important for several reasons. The aquaculture industry is rapidly growing around the world, and the demand for fish meal (a major ingredient in aquafeeds) is increasing. This is shown by the increase in the price of fish meal, which was $480 per ton in 2001, and is now over $2,000 (1). There is no indication that this trend will change anytime soon, as wildcaught fish (typical source of fish meal) levels have remained flat for decades (2). As shown in (2), fish production from aquaculture continues to grow, and co-products that result from farmed fish processing could serve to fill some of this void.
||Dry extruders have been used for decades to turn what would have been fish waste into high-quality ingredients for aquaculture diets. For example, Robinson et al. (3) worked with dry extruded soybean - fish coproduct mixes. The purpose of the research was to replace menhaden and catfish fish meals with the extruded soy/fish co-products, and to determine if they could be used to support catfish performance during a feeding trial. Mixtures of defatted soy and dehulled, full-fat soybeans were used alone, or in combination with liquid fish (hydrolyzed catfish offal) or catfish scrap.
These protein sources were extruded with an Insta-Pro 2000 extruder, and used in catfish diets to replace traditional fish meals. A catfish feeding trial was then conducted, and the growth responses to these recycled protein sources are shown below.
The result from a typical catfish diet is shown on the far left bar. Solvent-extracted soybean meal and menhaden fish meal made up the majority of the protein in this diet, and supported the least amount of catfish growth. When extruded soy (both defatted and dehulled, full fat) and catfish meal were the main protein sources, catfish growth was maximized (far right bar). Most of the improved growth performance appeared to be due to the extruded soy, as catfish meal had a lower protein efficiency ratio than menhaden fish meal (3). The extruded soy and menhaden fish meal had very similar protein efficiency ratios (3). Therefore, extruded soy contained high-quality protein when in catfish feed, which was shown when it was used alone (second bar from left) and nearly able to support the growth performance of extruded soy and fish meal (far right bar).
Incorporating fish co-products into soy before extrusion produced different results. Liquid fish was inferior to catfish scrap in terms of supporting weight gain (middle and middle-right bars above). As all of the diets in the growth study were formulated to contain identical total energy and protein levels, liquid fish likely contained lower levels of digestible amino acids than catfish scrap. This result demonstrates the importance of formulating fish diets on a digestible, rather than total, basis, and on having quality, well-defined supplies of raw materials. It may be necessary to comingle or test incoming raw materials, especially if several sources are used, to maintain consistent performance results. As the price of fish meal continues to stay elevated, or rise further, it may well be worth the effort.
High shear, dry extrusion has been used similarly with other aquatic co-products, such as shrimp heads and squid viscera (4). In addition, dry extrusion, when done properly, is effective at sterilizing co-products with notable microbial loads, such as poultry mortalities and hatchery waste (5).
Therefore, as small to medium fish feed producers turn to the new MS3000 Medium Shear Extruder for quality production at the right price, they may also consider recycling fish co-products to save on the high costs of fish meal. High shear extruders are not only the foundation of the MS3000 Medium Shear Extruder, but now more than ever allow fish farmers and fish feed producers to lower production costs.
1. Fish meal prices to remain prohibitively high for pig, poultry feeds, Ioannis Mavromichalis, PhD, Watt Ag Net
2. Global total fish harvest, Wikipedia
3. Evaluation of Dry Extrusion- Cooked Protein Mixes As Replacements for Soybean Meal and Fish Meal in Catfish Diets, Edwin H. Robinson, Julie K. Miller, Victor M. Vergara, Texas A&M University and Gary A. Ducharme, Triple “F” Inc., The Progressive Fish-Culturist, Volume 47, Issue 2, 1985
4. Processing of wet shrimp heads and squid viscera with soy meal by a dry extrusion process, Carver, L.A., Akiyama, D.M., Dominy, W.G., American Soybean Association Technical Bulletin AQ16, 89-4, 1989
5. Extrusion of Alternative Ingredients: An Environmental and a Nutritional Solution, Nabil W. Said, The Journal of Applied Poultry Research, Volume 5, Issue 4, Pp. 395 -407