Aquafeed Formulation

Aquafeed Formulation is the only resource that provides summaries with examples and formulation techniques specifically to meet the needs of anyone in the aquaculture industry.

As feed is the largest single cost item in aquaculture production, and formulating aquaculture feed requires many combinations of several ingredients and nutrient requirements, this book takes a clear-and -concise approach, providing essential information on formulation and covering relevant available software, feed nutrients, and additives such as enzymes and phytase and conjugated fatty acids, as well as best industry practices to improve aquafeed production.

Users will find this to be a one-stop resource for anyone interested or involved in, the global aquaculture industry.

• Includes the latest software evaluation for calculating protein and amino acid sources, trace minerals, and vitamins for aquaculture diets
• Provides essential information on formulation, covering feed nutrients and additives such as enzymes and phytase and conjugated fatty acids
• Presents factors affecting nutrient recommendations for aquaculture diets and nutritional effects on aquaculture nutrient excretion and water quality
• Covers a broad range of techniques to understand the nutrient recommendations in the NRC guide

• Language: English
• Publisher: Academic Press
• Release date: Oct 9, 2015
• ISBN: 9780128009956

Book preview

Aquafeed Formulation

Edited by

Sergio F. Nates

Table of Contents

Cover image

Title page

Copyright

List of contributors

Acknowledgments

Introduction

I.1 Introduction

I.2 Feed ingredients

I.3 Nutritional requirements

I.4 Feed ingredient testing

I.5 Feed additives

I.6 Feed formulation

I.7 Feed production and quality

I.8 Best practices in formulation

References

1. Overview of the aquaculture feed industry

Abstract

1 Aquafeed in Asia

2 Aquafeed in the Americas

Acknowledgments

References

2. Feed formulation software

Abstract

2.1 Introduction

2.2 General overview of the formulation process in the feed industry

2.3 LP-based feed formulation

2.4 Essential components of LP-based feed formulation software

2.5 Software options

2.6 Conclusion

Acknowledgments

References

3. Understanding the nutritional and biological constraints of ingredients to optimize their application in aquaculture feeds

Abstract

3.1 Introduction

3.2 Characterizing ingredients

3.3 Chemical composition of oils

3.4 Digestibility, palatability, and utilization value of plant protein meals

3.5 Nutritional value of plant and animal oils to aquaculture species

3.6 Processing effects of ingredients

References

4. Nutrient requirements

Abstract

4.1 Introduction

4.2 Proteins and amino acids

4.3 Lipids and fatty acids

4.4 Carbohydrates

4.5 Nutritional energetics

4.6 Vitamins

4.7 Minerals

References

5. Functional feed additives in aquaculture feeds

Abstract

5.1 Introduction

5.2 Phytogenics

5.3 Organic acids

5.4 Yeast products

5.5 Probiotics

5.6 Enzymes

5.7 Mycotoxin binders

References

6. Optimizing nutritional quality of aquafeeds

Abstract

6.1 Introduction

6.2 Sources of nutrient database

6.3 Nutrient levels and variability in commonly used raw materials

6.4 Impact of heat damage on the amino acid level and their variability

6.5 Proximate nutrients of raw material

6.6 Managing nutrient variation

6.7 Integration of Laboratory Information Management System and formulation

6.8 Summary

References

Index

Copyright

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Notices

Knowledge and best practice in this field are constantly changing. As new research and experience broaden our understanding, changes in research methods, professional practices, or medical treatment may become necessary.

Practitioners and researchers may always rely on their own experience and knowledge in evaluating and using any information, methods, compounds, or experiments described herein. In using such information or methods they should be mindful of their own safety and the safety of others, including parties for whom they have a professional responsibility.

To the fullest extent of the law, neither the Publisher nor the authors, contributors, or editors, assume any liability for any injury and/or damage to persons or property as a matter of products liability, negligence or otherwise, or from any use or operation of any methods, products, instructions, or ideas contained in the material herein.

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ISBN: 978-0-12-800873-7

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List of contributors

Girish Channarayapatna,     Evonik (SEA) Pte. Ltd, Singapore

Girish Channarayapatna holds a Bachelor degree in Veterinary Science and Master degree in Poultry Science from University of Agricultural Sciences, College of Veterinary Medicine, Bangalore, India. He completed his PhD program in 2009 from University of Guelph, Animal and Poultry Science Department, Canada. His main research focus during his Master’s and PhD program was on characterization and prevention of mycotoxicoses in poultry. He joined Evonik Industries in March 2010 and worked as the Technical Sales Manager for Asia South region for almost 4 years. He took over the new position as Director, Nutrition and Technical Sales for Asia South region from Jan 2014. He has published 6 scientific articles in peer-reviewed journals, 2 book chapters, 1 review article and several proceeding papers, abstracts and popular press articles.

Pedro Encarnação,     Biomin Singapore Pte Ltd, Singapore

Dr. Pedro Encarnação has an extensive background in aquaculture and nutrition. He has been involved in several research projects focusing on the improvement of feed formulations for aquaculture species and improving animal performance by the use of feed additives. He has an Honors Degree in Marine Biology and Fisheries and an MSc in Aquaculture from the University of Algarve (Portugal), and obtained is PhD in Animal Nutrition from the University of Guelph (Canada).

He has been in Asia for more than 9 years as Biomin Director of Business Development for the Aquaculture industry.

Brett Glencross,     Ridley Agriproducts, Narangba, Queensland, Australia

Dr. Brett Glencross is the Technical Manager with the Aqua-Feed Division of Ridley, Australia’s largest provider of animal nutrition solutions and products. He joined Ridley in March 2015 after 20 years in academia as a researcher. Prior to joining Ridley he was the Senior Principal Research Scientist for Aquaculture Feed Technologies research within the Aquaculture Research Program of the Commonwealth Scientific and Industrial Research Organisation (CSIRO) in Australia from 2009 to 2015. He has Honours and Masters Degrees in Biochemistry from the University of Western Australia and a PhD in Animal Nutrition from the University of Queensland.

Karthik Masagounder,     Evonik Industries AG, Hanau-Wolfgang, Germany

Karthik Masagounder has obtained his Bachelors in Fisheries Sciences and Masters in Aquaculture from India and PhD from the University of Missouri-US focusing on fish nutrition. After PhD, he continued his postdoctoral research in the US for another 2 years. He has published more than 15 papers including 8 peer-reviewed journal papers. Karthik has been working with Evonik Industries in the Asia South region as a Regional Technical Sales Manager from Jan 2012 until May 2015. Recently, he moved to Germany and started as Research Manager in Aqua Nutrition with Evonik Industries.

Zuridah Merican,     Aqua Research PLC, Singapore

Zuridah is the editor and publisher of Aqua Culture Asia Pacific, a magazine that strives to be the beacon for the regional aquaculture industry. She is well known and highly recognised by the public sector, academia and the industry in Asia, primarily and the rest of the world. She has been providing information to the Asia Pacific industry for the past 11 years. She is based in Kuala Lumpur. She began her career in aquaculture and fisheries with the Department of Fisheries, Malaysia in 1977. While in Singapore, she carried out assessments on the mariculture industry and a review on the feed industry in Asia. This was followed with consultancies on the industry in Asia for European companies. When she was based in Europe, Zuridah was the editor of UK based International Aquafeed Magazine for four years and then Asian Aquaculture for three years when she returned to Asia.

César Molina-Poveda,     GISIS, Guayaquil, Ecuador

César Molina-Poveda has a B.Sc. with honors in Chemist, a M.Sc. in Shellfish Biology, Fisheries and Culture from Bangor University (UK), and Ph.D. in Science and Technology of Animal Production from Polytechnic University of Valencia (Spain). He has also completed training courses at Mie University and the National Research Institute of Aquaculture (both in Japan), and Artemia Referent Center at Ghent University (Belgium). His expertise in shrimp and tilapia aquaculture has built from 24 years’ experience of applied research in both academic and industrial background, which includes nutrition studies and grow-out production management.

Sergio F. Nates

Dr. Nates is currently the President of the Latin American Rendering Association and the former President & CEO of the Fats and Proteins Research Foundation. He is also the former Vice-Chairman of the Animal Co-Products Research and Education Center (ACREC) at Clemson University. Dr. Nates is a member of the Board of Directors of the Global Aquaculture Alliance and the Chairman of the Feed mill Certification Committee – GAA.

Over the last twenty years of his career, Sergio has specialized in assisting the development of responsible fishing and aquaculture practices. He has also developed and implemented comprehensive management and research programs worldwide; product development, ingredient value models, formulation standards and quality assurance programs. He is the author of several book chapters and over 100 publications.

Sheila Ramos,     Evonik (SEA) Pte. Ltd, Singapore

Sheila Ramos works for Evonik Industries as a Technical Sales Manager for the Asia South region. Sheila received her B.S. in Agriculture, majoring in Animal Science, and M.S. in Animal Nutrition from the University of the Philippines at Los Baños. She has been with Evonik for almost 11 years, and is popular in the region in helping the feed industries to improve their feed quality with Evonik’s analytical services. Sheila has been a speaker in various conferences and has published more than 15 papers related to raw material and feed quality as well as advanced amino acid nutrition concepts.

Ingolf Reimann,     Evonik Industries AG, Hanau-Wolfgang, Germany

Dr. Ingolf Reimann works for Evonik Industries as Head of Analytical Services for the Animal Nutrition business. He received his degree in Analytical Chemistry from University of Duesseldorf, Germany. Ingolf has been with Evonik since 2002. His focus is to provide the feed industry globally with accurate and fast analytical services including AMINOLab and AMINONIR, the handling of analytical data and the extraction of value out of analytics.

Dagoberto Sanchez,     AppliedAquaNutrition Consulting, Lima, Peru

Dr. Dagoberto Sanchez is a Global Aqua Nutrition Consultant, located in Lima, Peru. He has 25 years of career in the aquaculture industry, feed formulation and manufacturing, with multifunctional experience in aquatic nutrition, R&D and aqua-farming. Prior to being a global consultant he supported Skretting as Latin America Business Development Manager and worked for 15 years as the Nutrition and R&D Director in Alicorp (Nicovita). He has an MBA in Peru and Masters Degrees in Mariculture from Texas A&M University and a PhD in Animal Nutrition from Texas A&M University in the USA.

A. Victor Suresh,     United Research (Singapore) Pte. Ltd, Singapore

Victor Suresh learned feed formulation at his first job with the Ralston Purina Company that he joined after completing his PhD in aquaculture at Southern Illinois University, Carbondale. In the course of his 20 year old professional career he has formulated feeds for aquatic species farmed in Asia and the Americas and has used four different software packages for feed formulation. He presently heads United Research, a firm specializing in formulation and R&D services in the feed sector, and lives in Singapore.

Acknowledgments

Sergio F. Nates

I would like to express my sincere gratitude to the authors. Their efforts to produce exceptional manuscripts and exciting contributions lie within the cover of this book. To Dr Victor Suresh for always listening and giving me words of encouragement. Thanks are due to all members of the staff of Elsevier involved in the preparation of this book.

Finally, no acknowledgments by me would be complete without a thank you to Dr Tom Zeigler, who introduced me to the field of aquaculture nutrition, and whose passion and leadership had lasting effects.

Introduction

Sergio F. Nates

I.1 Introduction

Rapid growth of aquaculture worldwide has become increasingly dependent upon the use of external feed inputs, and in particular upon the use of compound aquafeeds. In addition, changes in production technology and marketing, and changes in feed ingredients are key structural changes necessary for the aquaculture sector to grow (Tacon et al., 2011).

The aquaculture feed industry is responsible for converting raw materials of agricultural origin into feeds. These feeds are not only important in terms of cost but also in terms of nutrition, as some of these feeds are the primary source of animal and plant protein required by cultivated aquaculture species for normal development. In addition, this is a broad industry employing people with a variety of skills, including process engineers, economists, marketing experts, shellfish and fish scientists, regulatory experts, quality control technicians, and transportation and distribution specialists.

Feed is the largest single cost item in aquaculture production and since it accounts for 50–60% of the total cost, any saving on feed, though small, may greatly reduce the total cost and increase returns. Formulating aquaculture feeds requires the use of combinations of several ingredients since most feedstuffs have been shown to have significant nutrient and functional limitations and cannot be used individually at very high levels in the diets of most aquaculture species. Adopting local ingredient alternatives for the formulation of an aquafeed mix is a logical step for aquaculture producers to remain profitable. Challenges and obstacles include material availability, farming, initial cost competitiveness, and handling and processing. Consequently, feed formulation is an important aspect of the aquaculture industry and accurate formulation must be overcome before alternative aquaculture feed formulas can be fully developed successfully.

I.2 Feed ingredients

Use of locally available raw materials as ingredients in aquaculture feed contributes to a sustainable utilization of resources as well as potential growth in aquaculture production with less environmental impact. In addition, the evaluation of feed ingredients is critical to feed development. It is vital to discriminate the effects on feed intake from the effects on the utilization of nutrients from ingredients for growth and other metabolic processes (Glencross et al., 2007).

Ingredients used in practical aquaculture diets can be classified as protein (amino acid) sources; energy sources; essential lipid sources; vitamin supplements; mineral supplements; and special ingredients to enhance growth, pigmentation, or sexual development in the species, or to enhance physical properties, palatability, or preservation of the feed (Hardy, 2000).

The number of ingredients used to feed aquaculture species in different countries is very high. Moreover, there is considerable variability for each ingredient considering both its chemical composition and its nutritional value, as a result of factors associated with its production or processing. This situation justifies the development of national reference tables adapted to the specificities of each production system.

The ingredients studied are organized into the following groups:

1. Cereal grains and by-products

2. Fruits and tubers

3. Molasses

4. Vegetable protein concentrates

5. Fibrous foods

6. Concentrated animal protein

7. Fats, oils, and glycerin

8. Minerals and micro-ingredients

Likewise, all ingredients have advantages and disadvantages within a formulation. The advantages are normally associated with nutritional contributions, availability of essential nutrients (amino acids and lipids), and the disadvantages are related to antinutritional factors, the presence of contaminants, the presence of molds and the possible production of mycotoxins, low or variable quality, poor digestibility, susceptibility to oxidation, costs, availability, and sustainability.

With the significant exception of soybean meal, plant protein sources are generally nutritionally imbalanced in terms of essential amino acids, particularly lysine, and the first limiting amino acid in cereals. Unless supplemented with animal protein sources and crystalline amino acids, plant-based diets may not meet the requirements for critical amino acids for most commercial aquaculture species, especially carnivorous ones.

On the other hand, animal protein ingredients are normally used to balance the amino acid contents of diets and to increase protein content of the final feed. In many countries, feed manufacturers ensure that animal protein ingredients do not fall below minimum levels in fish and shrimp diets, especially for the larvae and juvenile stages whose amino acid requirements are high. The requirements for essential amino acids are progressively reduced as animals grow older, and it is possible to meet the needs of adults with diets containing lower levels of animal protein and relatively higher levels of plant protein. Fish meal, poultry meal, feather meal, and blood meal are the animal protein sources most widely used in aquaculture diets.

There is also a vital need to seek effective ingredients that can either partially or totally replace fish meal and other ingredients as protein sources in aquafeeds. Algal products can be used to enhance the nutritional value of food and animal feed owing to their chemical composition (Dewi et al., 2014); they play a crucial role in aquaculture (Jamali and Ahmadifard, 2015).

I.3 Nutritional requirements

The nutrient balance of feed ingredients influences feed utilization and growth of aquaculture species, and there is generous information on the nutrient content of feed ingredients produced by different industries worldwide. However, many requirements are, at best, only rough approximations of the optimum amounts of nutrients for practical diets to grow aquaculture species to harvestable size. Management, environmental factors, and size can have an effect on dietary nutrient levels for optimum performance. Nevertheless, nutrient requirement data that are available serve relatively well as a basis to formulate highly productive, economical diets for commercial aquaculture. In formulating a diet for a species where nutrient requirements are not known, the requirements for a related species whose nutrient requirements are known can be used. Generally, most variation of nutrients required among classes should be expected between warm- and coldwater species, fresh- and saltwater species, and finfishes and crustaceans.

It is essential to know the nutritional requirements, particularly for protein, lipid, and energy, for optimum growth of the species as well as in formulating a balanced diet. Improper protein and energy levels in feed increases production cost and deteriorates water quality. Insufficient energy in diets causes protein waste due to the increased proportion of dietary protein used for energy and the produced ammonia can reduce the water quality. Moreover, feed ingredients should deliver the necessary nutrients in amounts to meet the requirements of aquaculture species (Tacon, 1987). However, the amounts of total amino acids contained in feed ingredients are often much higher than the amounts that are digestible. Feed formulations based on digestible amino acids have been shown to increase body weight gain and feed intake and can improve body composition.

According to a study published by FAO (2003) protein is the key building block for feed formulation systems and the main and most expensive component of feeds (Shiau, 1998). Besides, the concept of an ideal protein used as a method of determining the essential amino acid requirements of fish species was first suggested by Wilson (1989). The dietary essential amino acid requirements determined using the ideal protein concept (based on the whole-body essential amino acid pattern) can serve as a valuable index for formulating the diets of cultivated aquaculture species until their dietary essential amino acid requirements are empirically established using amino acid test diets (Wilson, 1991).

Qualitative amino acid requirements appear identical for all fish species examined; arginine, histidine, isoleucine, leucine, lysine, methionine, phenylalanine, threonine, tryptophan, and valine are all required for normal growth and metabolism (Wilson and Halver, 1986). On the other hand, several studies have shown that shrimp require 10 essential amino acids: arginine, methionine, valine, threonine, isoleucine, leucine, lysine, histidine, phenylalanine, and tryptophan (Lim and Akiyama, 1995; Lovell, 2002; Fox et al., 2006).

Lipids are a group of natural organic compounds comprising fats, oils, phospholipids, and sterols. Dietary lipids are utilized in fish as a major energy source to spare proteins, provide essential fatty acids needed for proper functioning of many physiological processes and maintenance of membrane fluidity and permeability as well as for growth and survival. Dietary lipids also influence the flavor and texture of prepared feeds and flesh quality (Stickney and Hardy, 1989). In addition, dietary lipids are a highly digestible and concentrated source of energy that supplies 8–9 kcal/g, about double that supplied by either carbohydrate or protein (Chuang, 1990).

Carbohydrates are a source of cheap energy, but the ability of aquatic organisms, including shrimp and fish, to utilize them is limited (Shiau, 1997). This is due to a lack of ability to digest and regulate plasma glucose concentrations (Zainuddin and Aslamyah, 2014). The use of carbohydrates by fish and shrimp is less efficient than by land animals (Mohapatra et al., 2003). In addition, fish are known to have a limited ability for digestion and metabolism of carbohydrates and hence, excessive intake of this nutrient may result in nutritional problems (Hemre et al., 2002). Excess carbohydrates reduce the growth rate and are often accompanied by poor feed utilization (Zhou et al., 2015).

I.4 Feed ingredient testing

Proximate analysis is usually the first step in the chemical evaluation of a feed ingredient, where the material is subjected to a series of relatively simple chemical tests so as to determine the content of moisture, crude protein, lipid, crude fiber, ash, and digestible carbohydrate.

In vivo methods for feed ingredient testing require time-consuming trials with many live animals. In vitro methods, however, allow the quick assessment of nutritional value as well as the potential negative effects of any antinutritional compounds in the test material. In vitro pH-stat determination of digestibility is a promising new test technique. The new in vitro pH-stat assay simulates the digestion of a protein source by the enzymes of the target animal. Digestible energy cost per unit energy is the dominant cost pressure in the formulation of aquaculture diets, so it is pertinent to focus on the development of an assay for the assessment of available energy. As digestible energy is the easiest available energy parameter to measure in feed ingredients for shrimp and fish, it is a logical parameter on which to focus for this type of analysis.

On the other hand, many in vitro assays have been used with varying degrees of success to evaluate protein and ingredient quality, including the potassium hydroxide solubility test, nitrogen water solubility test, urease assay, and pepsin digestibility assay. Of these, probably the most common and rapid in vitro digestibility test for measuring protein quality is the pepsin digestibility assay that dates back to the early 1950s. A considerable body of research data relating protein to secondary productivity return in livestock has amassed since the mid-1940s. Yet, as good a predictor of productivity as the pepsin digestibility test is, when protein levels are constant but animal protein sources vary, productivity differences are seen.

Some methods are better at predicting digestible amino acids in vegetable and animal proteins. Protein analyses of animal excreta have shown that less-productive animals excrete higher levels of protein than more-productive animals. The quantity, not the digestibility, of the protein is expressed in such tests. Indeed, digestibility not only varies by source of protein but also within a category. For example, one fish meal can be more digestible than another. As a result, the original 0.2% pepsin method came about. However, studies have shown that pepsin digestibility analysis turns out higher digestibility rates than metabolic studies suggest, although more dilute concentrations have been used in an attempt to correct for this difference. In essence, there is no reliable mathematical relationship between the digestibility of one pepsin dilution and another.

The evaluation of aquafeed ingredients may benefit from recent advances in methodologies applied to the in vivo and in vitro measurement of digestibility in feeds for terrestrial animals (Cruz-Suárez et al., 2007; Lemos et al., 2009). One promising technique is the pH-stat in vitro determination of digestibility of feeds and feed ingredients. The assay simulates digestion of a protein source by the enzymes of the target animal. A significant correlation between the pH-stat in the in vivo and in vitro digestibility values exists when proteins from the same animal or plant origin are compared (Lemos and Nunes, 2007). The relatively low-cost method provides accurate results, is not environmentally affected, and enables a higher number of analyses than live animal experiments for a given time (Lemos et al., 2000).

Important to note is that some ingredients have a unique set of amino acids, along with other unwanted compounds, that contributes to the ration. The unwanted compounds, called antinutritive substances, can interfere with the digestion of the amino acids and therefore reduce the value of the ingredients. Moreover, predictions of the digestibility of ingredients can be inaccurate because the relationship between in vivo and in vitro digestibility can be different. The physical structure of ingredients can be partially inaccessible to enzymatic action or the presence of antinutritive substances. Enzymes split protein at specific junctions, but some antinutritive substances block these junctions, preventing proper digestion and reducing the value of the ingredient in a feedstuff. Cross-linkage formation reduces the rate of protein digestion, possibly by preventing enzyme penetration or blocking the sites of enzyme attack. Another interaction that can affect the results of digestibility analyses is the formation of complexes between starches and lipids. Such formations, which can occur in situ in the digestive tracts of several aquatic species, are thought to decrease digestibility and response to ingested carbohydrates.

I.5 Feed additives

Many feed additives are available that can improve fish and shrimp growth performance. Products that improve feed efficiency are particularly important since feed costs are a major expense in aquaculture production. Proper use of these products can improve aquaculture profits. Feed additives may be both nutritive and nonnutritive and work by either direct or indirect methods on the animal’s system. Many of the products influence different systems and, therefore, the effects of one can be additive to another.

Attempts to use natural materials such as medicinal plants are widely accepted as feed additives to enhance the efficiency of feed utilization and aquaculture productive performance. Recently, medicinal plants and probiotics have been reported as potential alternatives, among other feed additives, to antibiotics in aquaculture diets (Dada and Olugbemi, 2013).

Phytogenics comprises a wide range of substances and thus has been further classified according to botanical origin, processing, and composition. Phytogenic feed additives include herbs, which are nonwoody flowering plants known to have medicinal properties; spices, which are herbs with an intensive smell or taste, commonly added to human food; essential oils, which are aromatic oily liquids derived from plant materials such as flowers, leaves, fruits, and roots; and oleoresins, which are extracts derived by nonaqueous solvents from plant material (Jacela et al., 2010).

Some additives, amino acids and their metabolites, and vitamins are important regulators of key metabolic pathways necessary for feed intake, nutrient utilization, maintenance, growth, immunity, behavior, larval metamorphosis, reproduction, and resistance to environmental stressors and pathogenic organisms in various aquaculture species (Tincy et al., 2014).

Nutraceuticals can act as buffering agents in biological systems by reducing the deleterious effects of stressors and by improving growth. High dietary protein supplementation has an enhancing effect against different stressors. Dietary supplementation of different vitamins (e.g., vitamins C and E) can mitigate stress in shellfish and finfish. Supplementation of nutraceuticals can also help in mitigating multiple stressors, including temperature, salinity, and exposure to pesticides, and augmented growth and modulated nonspecific immune functions (Manush et al., 2005).

Organic acids and their salts are generally regarded as safe and have been approved to be used as feed additives in animal production. The use of organic acids has been reported to protect shrimp and fish by competitive exclusion, enhancement of nutrient utilization, and growth and feed conversion efficiency (Romano et al., 2015). The organic acids in no dissociated form can penetrate the bacteria cell wall and disrupt the normal physiology of certain types of bacteria.

I.6 Feed formulation

Ingredients could be chosen from a well-known list when preparing a supplemental feed, so that a feed mixture having the desired crude protein content is obtained.

In addition, with increased computer capabilities and improved software, feed rations can be calculated in almost unlimited numbers. During the past few years, computer use has progressively increased to minimize the time needed for calculation of ration formulation (Al-Desseit, 2009). The use of linear programming for determining the least-cost formulation of feed based on current market prices and small changes in relative prices can cause significant changes in demand for available feed ingredients. The application of the programming techniques for feed formulation parallel to the introduction of intensive systems of animal production in many countries is essential. Developing extensive nutrient databases (based on wide-ranging research) can give a competitive advantage to a feed company (Gosh et al., 2011).

Linear programming to minimize feed cost with respect to a set of restrictions (requirements and ingredient minima and maxima) was developed in the 1950s (Baum et al., 1953). The techniques presently applied to feed formulation are essentially unchanged. In addition to finding the ingredient mixture to meet diet specifications at minimal cost, the sensitivity analysis option of Excel’s Solver routine can be used to determine the shadow prices of ingredients (Waldroup (mimeo, n.d.)). Shadow prices are the highest prices at which the ingredient would be included in the solution. Shadow prices can also be the low cost required for ingredients that are too expensive to come into the formula. Shadow prices can be used to develop usage curves relating ingredient prices to the amount of ingredient that would be used in a particular feed formula (Udo et al., 2011).

I.7 Feed production and quality

Balanced aquaculture feed production is a process where multiple variables are involved: raw materials, nutritional formulations, transportation, market performance, and we might even include climate, which undoubtedly also regulates the agroindustrial activities that delineate the supply and prices of agricultural by-products. However, when put in place, the key factor is the feed mill operation.

Feed mill operations are dynamic systems. Each element of that system and all their functions are interrelated to achieve one objective: a safe and well-balanced finished feed. Some of the factors that affect this dynamic could be unmanageable as market policies, and others as simple as adjusting screws. Nonetheless, as the aquaculture industry becomes increasingly conscious of costs and benefits, it is searching for more functional feeds, many of which are augmented with key ingredients and compounds that promote animal growth and survival. In addition, plant proteins are increasingly used as alternatives to proteins from animal sources. The optimum production of feedstuffs with optimum dry matter conversion of feed to weight depends largely on ingredient quality and nutrient availability for the species in question. The determination of digestibility of major nutrients is one of the main steps in the evaluation of their bioavailability for a given species. Measuring digestibility protein is the most important feed nutrient for aquaculture of high-value animals.

I.8 Best practices in formulation

Associated with the rapid growth of aquaculture, new intensive cultivation techniques have been used which generally have greater environmental impact than traditional culture techniques. However, this rapid increase occurred at a time in which the general public has an increased level of concern about the environmental consequences of human activity. In this regard, the production of aquaculture food products continues to be positive but it should consider the possible side effects of their increased activity on animal welfare and their impact on the environment. Thus the four pillars that will hold the aquaculture production venture are: food safety and quality, health and animal welfare, environmental integrity, and social responsibility (Tucker and Hargreaves, 2008).

In addition, several management techniques can be used in feed preparation, handling, and delivery that can affect animal performance and nutrient excretion, consequently affecting the surrounding environment. For instance, pelleting and reducing the particle size (grinding) of a ration increases the digestibility of the ration for aquaculture species, improves N and P utilization and reduces excretion by 5–15% each (Turcios and Papenbrock, 2014). With respect to the pollution generated by aquaculture, nitrogen and phosphorus are considered as waste components of fish farming, causing serious environmental problems. In addition, several fish excrete nitrogenous waste products by diffusion and ion exchange through the gills, urine, and feces. Decomposition and reuse of these nitrogenous compounds is especially important in aquaculture using recirculation systems due to the toxicity of ammonia and nitrite and the chance of hypertrophication of the environment by nitrate (Brown et al., 1999).

Several new technologies are being developed and tested to enhance the nutrient content or utilization of feed ingredients, or to alter the availability of nutrients in current commercial feeds. This includes enzymes, genetically modified feed ingredients, and feed processing technologies to enhance the availability of nutrients to meet the needs of specific animals and reduce excretion of nutrients. These specialty feeds and new technologies will provide nutrients in a proper balance that will allow precision-feeding of aquaculture species.

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