Topic 12 - Anti-nutritional compounds in forages → biosynthetic pathways Flashcards
Adverse effects of forages
Contamination with inorganic compounds
Mouldy forage (fungi, bacteria)
Narrow range of forages
Non-optimal dosage
Non-optimal nutrient and energy supply
Secondary plant metabolites
Anti-nutritional factors
Substances that when present in animal feed reduce the availability of one or more nutrients
Interfere with the utilisation of dietary nutrients in a variety of ways
No major role in primary metabolism (non-essential compounds)
Mainly secondary metabolites
Taxonspecific metabolites
Effects on animal species
Decrease voluntary feed intake
Reduce digestibility
Changes in metabolism
Poisonous effects → decreased production (or quality)
Classification
Animal nutrition: based on their effect on the nutritive value of feedstuffs and on biological responses in animals
Botany: biosynthetic pathway of plant metabolites
Carbohydrates with anti nutritive effects
Non-starch polysaccharides
Non-digestible oligosaccharides
Non-starch polysaccharides (NSP)
Major structural elements in the cell wall - mainly i forage legumes
Cellulose → low digestibility
Beta-glucans and arabinoxylans → high water absorption capacity → increased viscosity → sticky faeces syndrome
High proportion of NSP
decreased energy value and digestibility of the forage → decreased production
Prevention of NSPs
Application of forage mixtures or specific enzymes
Non-digestible olgiosaccharides
Raffinose, stachyose and verbascose
Most of the species do not have enzymes to digest them → pass unchanged to the colon → intestinal bacteria ferment them to gases →bloating effect
Mainly in fabaceous plants as stored nutrinets
Prevention of non-digestible oligosaccharides
Application of beta-glalactosidase enzyme
Phytic acid
A primary product of carbohydrate metabolism
Can form complexes with basic residues of proteins → interfere with the activity of enzymes and digestibility of other nutrients
Occurrence: cereals, pulse crops, and oil plants
Phytate
Can form complexes with a variety of minerals → reducing the availability of these nutrients
Phosphorous and inositol in phytate form → not bioavailable to non-ruminant animals
Occurrence: cereals, pulse crops, and oil plants
Poultry and pigs: low feed conversion
Ruminant: tolerant → phytase enzyme produced by rumen microorganimsms
Prevention of phytic acid and phytates
Application of phytase supplementation
Phenolics with anti nutritive effects
Tannins
Isoflavonoids
Tannins
Hydrolyzable and condensed tannins
Natural occurrence: field pea, field bean, sainfoin
Major effects astringent taste (depresses feed intake), precipitate proteins water insoluble complexes (decreased protein conversion rate), bounds with iron (iron deficiency)
Susceptible species: poultry, pig, horse
Tannin content of forage plants is generally low, no poisonous, but mild antinutritive effect
Isoflavonoids
Coumestrol, genistein, formononetin
Natural occurrence: soybean, lucerns, clovers
Susceptible species: cattle, horse
Effects of isoflavonoids
Similar to animal estrogen
Bind irreversible to estrogen receptors
Decreasing fertility – abnormal estrus cycle, abortion, sterility
Prevention of isoflavonoids
application of forage mixtures
Polyketides with anti nutritive effects
Euric acid
Euric acid
General compound in the Brassicaceae family
Mainly stored in the seed
Major effects: myocardial lesions (fatty infiltration)
Susceptible: All livestock species
Prevention of euric acid
application of double zero cultivars
Terpenoids with anti nutritive effects
Saponins
Glossypol
Saponins
Natural occurrence: species of Fabaceae family
Generally molecules have a bitter flavor irritation of mucous membranes
Susceptible species: ruminants, poultry, pigs
Effects of saponins
Produce foam in the rumen
Can enter into the lipid bilayer of membranes disintegrated membranes
Decrease rumen motility
Red blood cells are affected → haemolytic effect
Prevention of saponins
Application of selected cultivars, forage mixtures or drying
Glossypol
A sesquiterpene dimer of cottonseed
Absorbed from the GT and highly bound to amino acids, especially lysine, and to dietary iron
Susceptible species: all animals, but especially monogastrics, preruminants, immature ruminants, and poultry
Effects of glossypol
Renders many amino acids unavailable → affects enzymatic reactions
Effects on the cardiac, hepatic, renal, reproductive, or other systems
Green discoloration of egg yolk
Prevention of glossypol
High intake of protein, calcium hydroxide, or iron salts, and limited dietary glossypol concentrations
Azetoids with anti nutritive effects
Non-proteinogenic amino acids
Water soluble peptides of low molecular weight
Non-proteinogenic amino acids
Natural occurrence in Lathyrus species: Lathyrogenes (ODAP, BAPN, DAB)
BAPN can inhibite the collagen synthesis → damage of bones and connective tissue
Susceptible species: horse, cattle, poultry
Prevention of Non-proteinogenic amino acids
Heat treatment or consumption of foods containing sulphuric amino acids
Water soluble peptides of low molecular weight
Natural occurrence: in species of family lucern, clovers
Rapid digestion by rumen microbes slime production frothy bloat (distension caused by foam and gases)
Susceptible species: horse, cattle
Prevention of Water soluble peptides of low molecular weight
drying, ensilage, slow accustoming to fresh forage legumes
Protease inhibitors
Natural occurrence in legume seeds (soy bean, beans) and cereals
Mainly trypsin and chymotrypsin inhibitors
Amylase inhibitors → minor importance → impaired digestion of starch
Susceptible species: poultry, pig, carnivores
trypsin and chymotrypsin inhibitors
Form stable inactive complexes with the pancreatic enzymes → decreased protein digestion
When trypsin and chymotrypsin are reduced → pancreas stimulated to produce more digestive enszymes → hypertrophy of the pancreas
Prevention of protease inhibitors
heat treatment but trypsin inhibitors are less susceptible to heat
Lectins
Phytoheamagglutinins
Proteins that are generally present in the form of glycoproteins → have the ability to bind to specific sugars
Natural occurrence: in beans (highly toxic), field bean, pea, lupines (less toxic)
Susceptible species: monogastric species
Effects of lectins
Binding of lectins to epithelial cells → disorders of nutrient absorption → growth depressions
Prevention of lectins
Heat treatment
Glycosinolates
Sulphuric compounds from cysteine strong, hot flavor
Natural occurrence: species of Brassicaceae
If specific proteins → carcinogenic nitriles, or thiocyanates can also be produced
It can be excreted in the milk
Susceptible species: pig, cattle, poultry
Effects of glycosinolates
Isothiocyanates produced → irritation of skin and mucous membranes, goitrogen effect → disrupts the production of thyroid hormones (interferes with iodine uptake)
Low iodine uptake losing of weight, haemorrhagic symptoms in liver, enlarged spleen and kidneys, abortion
Prevention of glycosinolates
Application of double zero cultivars
Poisonous azotoids
Cyanogenic glycosides
Poisonous alkaloids
Cyanogenic glycosides
Natural occurrence: linseed, Sorghum spp., white clover
Inhibition of cell respiration
Prevention of Cyanogenic glycosides
Grazing, harvesting in optimal phenological stage, application of limited amounts in mixtures
Poisonous alkaloids
Lupinus species: quinolizidine type – Lupinine, pupanine → Lupine poisoning
Vicia faba: pyrimidine type – vicine, konvicine → favism
Prevention of Poisonous alkaloids
application of selected cultivars
