Animal nutrition - anti nutrional factors Flashcards
What are „Anti-nutritional factors“ or „Secondary substances“ in feeds?
Give up to 6 examples.
Anti-nutritional factors can be defined as a substance which, under practical circumstances, can impair some aspects of animal metabolism and produce adverse
biological or economic effects in animal production.
Examples are;
– protease inhibitors
– glycosides such as saponins
– tannins
– lectins or haemaglutinins
– phytin
– indigestible carbohydrates (β-glucans)
Protease inhibitors are
are medications/enzymes that act by interfering with enzymes that cleave proteins.
Most common Protease inhibitors are (2)
trypsin inhibitors,
also chymotrypsin inhibitors
Inhibitors form complexes with enzymes trypsin
and chymotrypsin -> reduce digestibility
Where are Protease inhibitors found?
Trypsin inhibitors are mainly in leguminous plants, like soyabeans, peas, field beans
– for example -> if peas or field beans are fed to pigs or poultry, use varieties containing less trypsin inhibitor, otherwise it will decrease performance
Activity of trypsin inhibitors can be reduced by
heating.
During manufacture of soyabean meal
– process the soyabeans in an autoclave for 40 minutes at 110°C
– roast soybeans for 2…3 minutes at 230°C
heat processing inactivates protease inhibitors
Glycosides are
crystalline compounds in which the saccharide component is linked to an alcohol or some other group
Are soluble in water, alcohol and acetone
Glycosides can be divided into (3)
– cyanogenetic glycosides (linamarin, vicine)
– glycosinolates or mustard oil glycosides
– amphipathic glycosides or saponins
Give an example of a Cyanogenetic glycoside
linamarin
from linseed/flaxseeds
Cyanogenetic glycoside - linamarin degrades in the presence of
moisture and the enzyme linamarase,
to D-glucose, acetone and hydrocyanic acid (prussic acid).
Linamarase is an
extracellular enzyme, and therefore the degradation of linamarin takes place only after
linseed processing, and cell wall breakage.
How to treat linamarin to render it safe?
Heating destroys linamarase and will not cause poisoning. Feeding unheated flaxseeds is dangerous!
All linseeds sold in products in grocery stores are heat treated.
Give an exmaple of a Cyanogenetic glycoside
vicine (and linamarin and amygdalin)
is present in common vetch (a nitrogen-fixing leguminous plant), also in field beans. tastes bitter and horses and poultry are particularly sensitive.
Affects the nervous system, digestive tract and causes rashes on the skin
Mustard oil glycosides are also called?
And are found in?
glycosinolates
contain sulphur, more than 100 are known
present in rape seeds, fodder kale, fodder rape
main glycosinolate compound is
progoitrin
content in rapeseeds depends on variety
degrades in the presence of the enzyme myrosinase, and produces mustard oil (isothiocyanate), which is toxic for animals
– inhibits the uptake of iodine by the thyroid gland into thyroxine, thyroid gland increases in size, haemorrhages in udder, urine changes to a red colour
The Enzyme myrosinase can degrade glycosinolates in what circumstances?
Enzyme myrosinase is active at 50…60°C, but is destroyed when the temperature is over 80°C.
“glycosinolate progoitrin degrades in the presence of the enzyme myrosinase, and produces mustard oil (isothiocyanate), which is toxic for animals”
Amphipathic glycosides also known as?
saponins
produce foam
are surface active and bitter substances, causing bloat in animals
present to some extent in leguminous (clover) leaves and shoots
Solanine is a
glycoalkaloid with properties of a fungicide and a pesticide (helpful to the plant)
where is solanine found?
is found in young potato sprouts and in potatoes that colour green due to the sun (content can rise up to 0.5%)
is poisonous for animals when the solanine content increases up to 0.05%
a potato normally contains 0.002…0.01%
Gossypol is a
yellowish fat-soluble pigment of cotton seeds (0.2%)
For poultry, cotton seeds and meal are dangerous when the content of gossypol is from 0.01%.
What animal should not be fed feed containing gossypol?
During the manufacturing process of meal, where the fat is extracted, gossypol is also removed.
During extrusion, some gossypol stays in the cake, and therefore should not be fed to non-ruminants.
A reddish-yellow colour of the meal or cake indicates a dangerous content of gossypol.
What are Lupine alkaloids
Lupin is a protein-rich grain legume used as livestock feed, containis alkaloids, which are a plant defensive mechanism against herbivores.
Examples of lupine alkaloids (4)
angustifoline,
lupinine,
lusitanine,
sparteine
Grain legume lupin can be divided into two, called
Bitter lupin and sweet lupin.
Bitter lupin contain alkaloids at more than 1.5…1.8% compared to sweet lupin, at 0.05%
Lupine alkaloids are poisonous.
What animals are most sensitive to alkaloids?
Horses and sheep are more sensitive to alkaloids than other animals.
– causes changes in the mucosa and disturbances of the nervous system
Tannins are
polyphenolic compounds, found widely in plants such as
– leguminous (field beans, peas), rapeseeds, sorghum (flowering grass), barley
Tannins Can be divided into (2)
hydrolysable or condensed tannins
condensed are more important in animal nutrition
Condensed tannins are not toxic per se, but they cause problems in animal nutrition. Why? (3)
– they can form complexes with feed proteins and enzymes, with carbohydrates, and with divalent ions, causing reduction in digestibility
– can increase intestinal epithelial erosion
– may reduce forage palatability (and feed intake)
How can tannins have a positive effect?
Could have a positive effect at certain levels (<9% DM)
– reduces likelihood of rumen bloat, increases the dietary amount of protein flowing to the duodenum, may reduce methane emission
- We cannot decrease the amount of tannins by processing (except for peeling), but can by plant breeding.
Lectins, also known as
haemagluttinins
Lectins or haemagluttinins are
glycoproteins named for their ability to agglutinate red blood cells
Where are lectins found?
present in leguminous seeds
– ricin**, soya beans **, peas **, field beans*
Lectins harm
intestinal wall and microvilli
The intestinal wall contains glycoproteins for which lectins, as they are also glycoproteins, have agglutinate properties and due to this they cling to the gut wall.
– cause bloody diarrhoea & toxicity
– decrease nutrient absorption, organism immunity and production
How are lectins destroyed?
Easily destroyed by heating
Phytin is
a phosphorous-rich substance in green plants
Phytin binds..?
metals (Ca, Co, Cu, Zn etc.), forms salts
60…70% of phosphorous in maize, sorghum, wheat, barley, oats, cakes and meals is found in phytin.
To split phytin and release phosphorus, what enzyme is required?
phytase
Phytase originates from?
Phytase is need to split phytin to release the phosphorus inside.
Phytase is of microbial origin, but is missing in monogastric animals, incl. poultry.
Due to this P assimilation is less than 25%.
To increase P assimilation, phytase of synthetic or microbial origin must be used in pig and poultry rations -> using supplemental phytase reduces environmental pollution of unassimilated phosphorus (unabsorbed and pooped out).
Indigestible carbohydrates, or oligo- or polysaccharides are mainly
β-Glucans
– barley and oats contain 4%, rye 2.5%, wheat 1% (oats hulls 5.5-23%)
β-glucans form sticky faeces together with
pentosans, which causes hygiene problems.
Pentosans are water soluble and make intestinal contents viscous, which blocks digesta movement and promotes feed microbial fermentation in the intestine.
Pigs and poultry cannot digest β-Glucans due to
a lack of specific digestive enzymes.
To digest β-glucans synthetic enzymes must be used in the rations of pigs and poultry.
– they increase the absorption of energy by about 10%
