Authors: Pooja Gupta Soni,Taramani Yadav, Sourabh Kumar, Manish kushwaha
Anti-nutritional/ anti-quality components- Those substance generated in natural feed stuffs by the normal metabolism of species and by different mechanisms(e.g. inactivation of some nutrients, diminution of the digestive process or metabolic utilization of feed) which exerts effects contrary to optimum nutrition. Common anti-quality components are Nitrate, Prussic acid, Oxalates, Saponins, Phyto-estrogens, Tanins and Mimosine etc.
1.0 Nitrate toxicity
Accumulation of Nitrate in Plants occurs when excessive supply of nitrogenous fertilizers applied to crops, Lack of Sunlight, during detrimental Weather, herbicides (2,4-D) and Diseases. Nitrate toxicity occurs in different fodder crops- Sorghum, Sudangrass, Maize, Oats, Barley etc.
Stage of Growth and Plant Parts also affect nitrate concentrations. Highest in young plants and decreases as the plant matures. The highest concentration of nitrate accumulates in the lower third of the plant stalk or stem. Stem > Leave s> Floral parts (order of nitrate accumulation).
Effect of Nitrate toxicity in animal
• Respiratory distress, bluish mucous membranes and death of animal
• An internal sign is the blood will be bluish chocolate brown in color.
Prevention of Nitrate Toxicity
• Consider making silage of drought damaged forage. The ensiling process reduces the nitrate level 40 to 60 percent.
• When a crop is grown under conditions that cause nitrate accumulation, delay harvest of the crop until conditions improve to permit nitrate content to drop to a safe level
• Have suspected forage tested before feeding to cattle.
• Dilute toxic forage by mixing it with nontoxic forages and/or energy feeds such as molasses or corn
2.0 Cyanogenic glycosides/prussic acid (HCN)
Factors Affecting Prussic Acid Content in Plants
• Species- Prussic acid content in sudangrass is about 40 percent less than in most other sorghums(Sorghum > sorghum-sudangrass > Sudangrass)
• Plant Parts- Leaf blades normally contain higher prussic acid levels than leaf sheaths or stems. Upper leaves have more prussic acid than older leaves.
• Maturity- Highest prussic acid levels are reached before the boot stage.
• Drought- Severe drought is probably the most common cause of prussic acid poisoning
• Fertilizer- High N rates are applied to soils deficient in phosphorus and potassium, prussic acid levels usually increase.
Avoiding Prussic Acid Poisoning
• Green Chop - Green chop forage is usually safer than the same material used for pasture because it is not selectively grazed.
• Silage- Much of the poison escapes as a gas during fermentation.
• Hay- Prussic acid content of sorghum hay decreases as much as 75 percent
• Do not allow hungry cattle to graze where prussic acid may be a problem.
• Never allow stock to graze sorghum that is less than 50 cm high.
• Saponins are glycosides with a distinctive foaming characteristic.
• Saponins are bitter and reduce the palatability of livestock feeds.
• saponins found in oats and spinach increase and accelerate the body's ability to absorb calcium and silicon.
• Saponins are generally not a problem in tropical forage legumes. However, they are common in several temperate forage legumes.
Saponins content in different crops
|Source||Saponins (% dry weight)|
Symptoms of Poisoning
• Saponins increase the permeability of the membranes of red blood cells. This membranes are destroyed and their hemoglobin escapes into the bloodstream.
• Bloat occurs in animals(Ruminants) grazing temperate legumes that contain saponins but not in livestock grazing tropical legumes
• In non- ruminants (poultry and swine)-retardation of growth rate
• Irritated mucous membranes of the mouth and digestive tract
• Low dietary protein quality (supplemental methionine will counteract this).
• Increased excretion of cholesterol.
Plants Containing Oxalates- Elephant grass, Buffel grass, Setaria grass, Sugarbeet
Effect and symptoms of oxalate poisioning
• It can bind with dietary Ca or Mg to form insoluble Ca or Mg oxalate, which then may lead to low serum Ca or Mg levels as well as to renal failure because of precipitation of these salts in the kidneys.
• Non-ruminants appear to be more sensitive to oxalate than ruminants (rumen bacteria help to degrade oxalate).
• Less than 2.0 % soluble oxalate- Ruminant, <0.5% soluble oxalate- Non-Ruminants is safe
• Gastro Intestinal irritation.
• Removal of calcium from blood - precipitated as calcium oxalate.
• Tetany (calcium deficiency).
• Weakness and recumbency (inability to stand upright without support).
Polyphenolic plant defense compounds that can form stable complexes with Proteins Carbohydrates, Minerals.
• 0 % in temperate grasses
• Up to 50 % in tropical browses but less than 5% in some tropical legumes
Selected Forage Plants with Tannins
• Calliandra calothyrsus
• Ideal concentration of condensed tannins in this forage legume is between 2–4% of the diet DM, at which level they bind with the dietary proteins during mastication and appear to protect the protein from microbial attack in the rumen.
• At higher levels (5– 9%) tannins become highly detrimental as they reduce digestibility of fibre in the rumen by inhibiting the activity of bacteria and anaerobic fungi.
• The phytoestrogen content varied from 1.0% to 2.5% of dry matter.
• Found in leguminase family – Lucerne, Berseem, Red clover, White clover.
• Low P in the soil also makes it more estrogenic.
Cattle have a lower susceptibility to the estrogenic effect of clover pasture than sheep
About Author / Additional Info:
I am currently pursuing Ph.D in Agronomy from ICAR-NDRI.