01. Fish Nutrition and Health Introduction .pdf

01. Fish Nutrition and Health Introduction .pdf

1. Fish Nutrition and Health

2. What is fish
•A fish is an aquatic vertebrate with gills, limbs (if
present) in the form of fins, and usually with a skin
covered with scales of dermal origin.
•Fishes do not form a monophyletic group.
•The common ancestor of fishes is also an ancestor of
land vertebrates
•With over 31,000 living species,
•Fish include more species than all other vertebrates
combined.

5. •They are adapted to live in a medium 800 times more
dense than air.
•They can adjust to the salt and water balance of their
environment.
•Their gills are efficient at extracting oxygen from water
that has 1/20th the oxygen of air.
•A lateral line system detects water currents and
vibrations, a sense of “distant touch.”
•Evolution in an aquatic environment both shaped and
constrained its evolution.
•“Fish” refers to one or more individuals of one species;
“fishes” refers to more than one species.
•Out of 9 living classes of vertebrates 5 are fishes
•Out of 64000 animal species ½ are fishes

6. Some salient physiological and
Nutritional features of fishes
•Modes of Respiration
•Lungs of lungfishes allow them to respire from air.
•Eelscan wriggle over land during rainy weather; they
use skin as their major respiratory surface.
•A bowfinuses gills at cooler temperatures and its
lung-like swim bladder at higher temperatures.
•The electric eel has degenerate gills and gulps air
through its vascular mouth cavity.
•The Indian climbing perch spends most of its time on
land, breathing air in special chambers.

7. Osmotic Regulation
•Freshwater fishes have far less salt than is in fish blood;
water tends to enter the body of the fish and salt is lost by
diffusion.
•The scaled and mucous-covered body is mostly impermeable,
but gills allow water and salt fluxes.
•The opisthonephrickidney (isthe adult kidney of
anamniotes-such as the shark and mud puppy -and develops
from all or most of the nephric ridge posterior to the pro-
nephros).
•Metanephrickidney is the adult kidney of amniotes -the
pigeon, cat and rabbit -and develops from a small posterior
part of the nephric ridge)pumps excess water out.

8. •Special salt-absorbing cells located in epithelium actively
move salt ions from the water to the fishes’ blood, hence
freshwater fishes are called hyperosmotic regulators
•These systems are efficient;
•a freshwater fish devotes little energy to keeping osmotic
balance.
•About 90% of bony fishes are restricted to either
freshwater or seawater habitats.
•Euryhalinefishes live in estuaries where salinity
fluctuates throughout the day.

9. Marine bony fishes are hypo-osmotic
regulators.
•Marine fishes have a much lower blood salt
concentration than in the seawater around them.
•Therefore they tend to lose water and gain salt; the
marine fish risks “drying out.”
•To compensate for water loss, a marine teleost drinks
seawater; this brings in more unneeded salt.
•Unneeded salt is carried by the blood to the gills and
secreted by special salt-secretory cells.
•Divalent ions of magnesium, sulfate and calcium are
left in the intestine and leave the body with the feces
or enter the bloodstream and are excreted by the
kidney.
•Marine fish excrete divalent ions by tubular secretion;
glomeruli are small or they are absent or missing.

10. Fig. 24.29

11. Osmoregulation in fishes

12. Feeding Behavior
•Fish devote most of their time searching for food to
eat
•With the evolution of jaws, fish left a passive filter-
feeding life and entered a predator-prey battle.
•Most fish are carnivoresthat feed on zooplankton,
insect larvae and other aquatic animals.
•Most fish do not chew food since it would block water
flow across the gills.
–Most swallow food whole; this is easy with water
pressure that sweeps food in when the mouth opens.

13. Feeding Behavior
•Some fish are herbivoresand eat plants and algae;
they are crucial intermediates in the food chain.
•Suspension feeders are a third group, and crop the
abundant microorganisms of the sea.
•Many of the plankton feeders swim in large schools
and use the gill rakersto strain food.
•Omnivorescan feed on both plant and animal food.
•Scavengersfeed on organic debris.
•Parasiticfishes suck the body fluids of other fishes.

14. Types of Environments determines fish
feeding behavior
•Marine, brackish and freshwater fish
Differences in osmotic cost to maintain homeostasis
•Coldwater and warm water fish
Differences in O
2content in water, plus availability of
natural food in ponds compared to 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 are present in digestive physiology
Feeds must be water-stable for slow eaters like shrimp

15. Feeding and Nutrition in fish
Prepared vs Live Feeds
•Different nutrients like protein, lipids,
carbohydrates, vitamins and minerals come from
feeds
•Fish food/ feed is of two types;
•Natural: Comprises living organisms
•Artificial: Comprises inert feed particles

16. What is Nutrition?
•Nutrition:the provision of all indispensable nutrients in
adequate amounts to insure proper growth and
maintenance of body functions or
•Nutrition= the study of food.
•Food= any substance which contains nutrients.
•Nutrient= any substance which can be digested and
used by the body.
•There are sixnutrients:
❖Proteins, Fats, Carbohydrates, Minerals, Vitamins,
and Water

17. ➢Some more useful definitions
➢Macronutrients= nutrients required in large amounts,
i.e. proteins, fats and carbohydrates.
➢Micronutrients= nutrients required in small amounts,
i.e. minerals and vitamins.
➢Composition: refers to the elements that make up the
nutrient and how they are arranged within the
nutrient.
➢Classification: refers to the division into groups or
classes.
➢Sources:refer to the foods which are the best
suppliers of the nutrient.
➢Functions: refers to the uses of the nutrient in the
body.

18. •All the nutrients:
•involve various chemical reactions and physiological
transformations which convert foods into body
tissues and activities
•involve ingestion, digestion and absorption of various
nutrients
•transport into cells
•removal of unusable elements and waste products of
metabolism

19. History of Nutrition
•Lavoisieris generally credited as being the “father”
of nutrition
•Until the first quarter of 19th century, we thought
the nutritive value of food resided only in one
component
•Near the end of the 19th century research started to
focus primarily on the need for protein, lipids and
carbohydrates
•Minerals were considered important, but their
essentiality was unknown

20. History of Nutrition
•Tremendous expansion in the 20th Century with the
discovery of vitamins, role of amino acids, more
minerals
•The body is now known to need more than 40
nutrients for normal growth and maintenance
•What have been the reasons for these advances???
•Human nutritional/health problems
•Also, basic studies of the functioning of the animal/
organism supplemented research

21. History of Nutrition
•Example of historical nutritional research:
•Heifers (young cow) fed wheat-based diets produced
calves (young-ones) at lower rates than those fed
corn diets
•Assumption:something toxic in wheat
•Analysis: nothing toxic in tissues
•Reality: vitamin deficiency
•Scientific methods for formulating feeds were
inadequate
•Research diets were eventually simplified/purified

22. History of Nutrition
•First vitamin discovered in 1913 (Frederick GowlandHopkins found
unknown factors present in milk that were not fats, proteins, or carbohydrates, but
were required to aid growth in rats)
•Pioneer nutritional work achieved primarily through the
use of animal subjects
•Same today, but with restrictions
•Rats were used to determine ➔vitamins, amino acids,
minerals requirements
•Dogs used for determination of ➔insulin, nicotinic acid
•Guinea pigs used ➔prevention of scurvy
•Chicks were used for determination of ➔thiamin and
other vitamins
•Bacteria were used to determine ➔growth factors,
nutrient function in metabolism
•Final answers must be derived from species studied

23. Nutrition Today
Animal nutrition today is multidisciplinary:
•Metabolism: physiologists, biochemists
•Vitamins: organic chemists
•Isotopes/chromatography: physicists
•Protein structure: molecular biochemists
•Breed variation: geneticists
•Vitamins/amino acids: microbiologists
•Additives/improved digestibility: food technologists

24. Nutrient Essentiality
•Essential nutrient: one that must be provided in the
diet in order to insure adequate growth and
maintenance, indispensable
•Nutrient categories: macro and micro
•macronutrients:protein, lipid, carbohydrate, etc.
•micronutrients: trace metals, vitamins
•important: molecular weight is not the basis, of the
requirement of any nutrient
•For macronutrients requirement level is e.g. in case of
•proteins: g/kg while in micronutrients like vitamins:
µg/kg
•large requirement doesn’t imply greater importance
(example: B
12in some fish 0.4 µg/day)