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Fish Nutrition Research Differences and similarities with livestock

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Fish Nutrition Research
Differences and similarities with
livestock nutrition and what the
future holds. Part I.
Ronald W. Hardy, Director
Aquaculture Research Institute
University of Idaho
University
of Idaho
Topics to cover
•
•
•
•
Differences between fish and livestock
Brief history of fish nutrition
Brief overview of evolution of fish feed
manufacturing
Today’s hot topics in fish nutrition
–
–
–
•
Replacement of marine protein and oils
Effects of nutrition on food quality and fish health
Microparticulate feeds for small fish larvae at first feeding
Opportunities presented by developments in
molecular biology
Fish Facts
•
•
•
•
•
Fish evolved in a very diverse environment,
and 20,000 species exploit every possible
niche
Currently, there are ~140 species fish being
farmed
First publication on fish farming was 2500 BC
In 2005, 43% of all fish consumed globally
was produced by farming
Aquaculture production growing at 9-10%
annually, fastest sector of animal production
Differences among farmed fish species
•
Marine, brackish and freshwater fish
•
Coldwater and warmwater fish
– Differences in osmotic cost to maintain homeostasis
– O2 content in water, plus availability of natural food in
ponds compared trout raceways or marine net-pens
•
– metabolic rate and temperature tolerances
– membrane fluidity that influences fatty acid requirements
Fish and crustaceans (shrimp, crabs)
– Huge differences in mechanisms of locating feed
– Shrimp are external masticators, fish gulp feed
– Differences in digestive physiology
– Feeds must be water-stable for slow eaters like shrimp
Fish vs. livestock and poultry
•
Major differences associated with aquatic
existence
– Fish maintain neutral buoyancy and do not need skeletal
and muscular systems to oppose gravity
•
– Fish excrete ammonia
– Fish are cold-blooded
Other differences
– Fish exhibit indeterminate growth
– Huge differences in digestive system among farmed fish
•
Fish are monogastric, but…
– Gastric stomached fish (carnivores like salmon/trout)
– Agastric (carp)
Fish vs. livestock and poultry:
differences associated with aquatic existence
•
Fish exist in neutral gravity, no need for
heavy skeleton
– Dietary calcium and phosphorus needs are lower
– Energy expenditures for locomotion are lower
•
Fish excrete ammonia via the gills
– Lower metabolic cost than excreting urea or uric acid
– Higher caloric energy yield from metabolism of amino
acids
•
Fish are cold-blooded
– Upside: no need to stay warm
– Downside: rates of metabolism, digestion, etc. decrease
in cooler water, plus membrane fluidity must change
Fish vs. livestock and poultry:
differences in physiology
•
Many fish exhibit indeterminate growth
– Growth continues after first maturation and
spawning
– Hypertrophy and hyperplasia (make new muscle
cells)
•
Fish are monogastric (few herbivorous fish)
– Some fish have an acid stomach
– Other start with an acid stomach, then lose it as
fingerlings
– Some are stomach-less (agastric)
Fish vs. livestock and poultry:
differences at start of exogenous feeding
•
Some fish spawn large eggs
– Salmon & trout (2000-15,000 eggs/female)
– Incubation requires 50-100 days depending on water
temperature
– First feeding fry are 200-400 mg and can be fed small,
particulate feed
•
Many fish spawn very small eggs
– Most marine species (> 1 million small eggs per female)
– Incubation requires 3-7 days
– First feeding fry are very small and must be fed live-feed
through metamorphosis or until reach a decent size
– It is very challenging to provide adequate nutrition via live
feed
•
•
Right live feed at the right time
Correct nutritional content of live prey ( need PUFA enrichment)
Cod eggs
Copper rockfish larvae at first feeding
Canary rockfish larvae with feed in gut
six weeks after first feeding stage
Fish vs. livestock and poultry:
other nutritional differences
• Fish nutritional requirements
– Ascorbic acid
– Polyunsaturated fatty acids (PUFAs)
– Many minerals obtained via the water
• Carnivorous species have a limited ability
to utilize or metabolize starch
– They evolved using protein and lipid for metabolic
energy
Efficiency of fish compared to
livestock
•
•
•
•
•
FCR values less than 1.0 for fish
FCR values 1.6-1.8 for chickens
FCR values 8-10 for cattle
Yield of high-quality protein from salmonids
is 55%
Total yield from poultry or cattle is lower and
quality varies with cut
Brief history of fish nutrition
•
Prior to 1950s:
–empirical feed formulation research with a variety
of ingredients
–Nutritional diseases quite prevalent
–Little solid information on nutritional requirements
•
1950s and 60s:
–“Golden age” due to development of semi-purified
diet that allowed single nutrients to be deleted and
added back (Halver’s PhD work)
–Vitamin and amino acid requirements of salmon
and trout were discovered
–Common nutritional diseases eliminated
Brief history of fish nutrition
•
1970s :
–Essential nutrient list expanded to other species
–Refinement of nutrient requirement estimates using new
approaches to assess nutritional adequacy
•
1980s and 90s: Aquaculture production takes off
•
2000 until now
– Need for economical and efficient grow-out feeds
– New species including those with larval stages
– Low-pollution feeds (low-phosphorus, highly digestible)
–Main story is alternative protein and lipid sources
–Sub-plot is supplements to enhance disease resistance, provide
“semi-essential nutrients” and to produce healthful products (low
in POPs, high in omega-3 fatty acids)
Dietary nutrient requirements:
Pioneering fish nutrition research
• Development of semi-purified diet
•
(1953) that supported normal growth
Establishment of quantitative dietary
requirements of vitamins & amino
acids (1960s)
– USFWS Western Fish Nutrition
Laboratory
• John Halver & colleagues
• Pacific salmon were focus, hatchery support
• all work was conducted with fry & fingerlings
Vitamin requirements of salmon and growing
chickens (IU or mg/kg dry diet)
Vitamin
Vitamin A
Vitamin D
Vitamin E
Vitamin K
Thiamin
Riboflavin
Pyridoxine
Pantothenic acid
Niacin
Biotin
Folic acid
Vitamin B12
Ascorbic acid
Choline
myo-Inositol
Salmon/trout
2500
2400
50
unknown
1
7
6
20
10
0.15
2
0.01
50
800
300
*values in yellow are lower for chickens
Chickens
1500
200
16
0.5
1.3
3.6
3.0
10
11
0.10
0.25
0.003
not required
500
not required
Semi-purified diet for salmonids
Ingredient
Percent in diet
Vitamin-free casein
Gelatin
Dextrin
Wheat starch
Carboxymethylcellulose
Alpha-cellulose
Mineral mixture
Vitamin mixture
Amino acid mixture
Choline chloride (70% liquid)
Herring oil
40.0
8.0
10.0
10.0
1.3
6.0
4.0
3.0
2.0
0.3
17.0
Proximate
category
Percent
Moisture
28-30
Crude protein 34
Fat
17
Ash
5
Determining nutrient requirements in fish
•
•
Feed semi-purified diet, adding back graded
levels of single essential nutrient
measure response variables
– growth, feed conversion ratio, survival (1950’s)
– tissue nutrient levels, assuming that they plateau at
requirement level (1950’s through today)
–
–
–
measure activity of enzymes that require essential nutrient
as co-factor (same assumption, 1980’s)
measure excretion of nutrient or metabolites (1990’s)
Nutrigenomics (study of effects of nutrients on gene
expression and single gene products in tissues)
Qualitative
dietary
arginine
requirement
(Halver)
Relationship between thiamin
intake and liver thiamin
concentration
Nutrient requirements of salmonids
•
•
•
•
•
•
•
Protein
Ten essential amino acids
Lipids
Omega-3 fatty acids (1% of diet)
Energy
Supplied mainly from lipids and
protein
Vitamins
15 essential vitamins
Minerals
Carotenoid
pigments
10 minerals shown to be essential
Needed for viable eggs
NOTE: Other minerals are probably essential but can be obtained
from rearing water
Criteria or method used to establish a
dietary vitamin requirement affects value
•
•
•
Response variable
– absence of deficiency sign (minimum level)
– tissue saturation or plasma level
– enzyme activity
Statistical evaluation
– broken-line (Almquist plot)
– curve-fitting and models
• fit curves but are they biologically relevant?
• do we chose 95% or 100% response as requirement?
Real-world environmental conditions
– crowding, water quality, pathogen load etc.
Ascorbic acid requirements of salmonids
Requirement*
Comments
15-20 ppm
Prevents deficiency signs
250-500 ppm
Supports maximum wound
healing activity
1000-2500 ppm
Supports maximum disease
resistance in laboratory
challenges
>2500 ppm
Maximum tissue storage levels
and max. immune response
* When included in purified diet, with ideal conditions and no
oxidation of vitamin C
Mineral requirements of fish
Macrominerals (g/kg diet)
Microminerals (mg/kg diet)
(trace elements)
Calcium
Phosphorus*
Sodium
Potassium*
Chlorine
Magnesium*
Sulfur
Iron
Manganese*
Copper
Zinc*
Cobalt
Selenium*
Iodine*
Molybdenum
* Required in the diet, but not always supplemented in practical feeds
Carotenoid pigments in farmed salmon
and trout feeds
Synthesized products
Carophyll red
Carophyll pink
Natural products
Krill meal
Phaffia yeast
Marine algae
Crustacean waste (crab, shrimp, crayfish)
Note: astaxanthin shown to be essential nutrient for
salmon to produce viable offspring
Nutrient requirements – Halver’s
contribution
•
•
Complete estimates of nutrient requirements only
done for juvenile Pacific salmon and rainbow trout
Halver’s work never duplicated for Atlantic salmon
–Dietary requirements still based on Pacific salmon work
•
Atlantic salmon production
– >1,200,000 metric tons
– ~2,000,000 metric tons of salmon and trout feed per year
•
The nutritional information upon which this industry
is based is that of Halver and his colleagues
Changes in protein and fat
levels in trout feeds
50
40
30
Protein
Digestible Protein
Fat
20
10
0
1970
1980
1990
2000
2006
Changes in protein and fat
levels in salmon feeds
60
50
40
Protein
Digestible Protein
Fat
30
20
10
0
1960s 1970s 1980s 1990s
2000
Changes in feed conversion
ratios for salmon and trout
2.5
2
1.5
Salmon
Trout
1
0.5
0
1970
1975
1980
1985
1990
1995
2000
The
authoritative
text for all fish
nutritionists
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