EXOGENOUS TOXICANTS IN POULTRY NUTRITION
Mycotoxins:
Some of the important mycotoxins are aflatoxins, Ochratoxin A, T-2 toxin, rubratoxin B and citrin. Aflatoxin B1 is most pathogenic to poultry as compared to other aflatoxins viz. B2, G1 and G2. Aflatoxin toxicity (aflatoxicosis) has been reported to cause serious health hazard to poultry and other avian species. Aflatoxicosis in chicken is characterized by listlessness, anorexia, poor pigmentation, jaundice and dehydration of combs and shanks. Sensitivity or resistance to aflatoxins is inherited as distinctive characteristics of breed and strain. The adverse effect of aflatoxins on performance of chicken is also dose and time related. This toxin is primarily a hepatotoxin in young broiler chicken. One effect that is used as a diagnosis of aflatoxicosis in poultry is an enlarged, fatty, yellow and friable liver that occurs in broilers when they consume aflatoxins contaminated feed. This mycotoxin is also a nephrotoxin and some kidney pathology does results during aflatoxicosis. Aflatoxins affect the commercial poultry production in many ways: (a) reduce body weight gain; (b) make birds more susceptible to brushing; (c) decrease egg production, egg weight and hatchability; (d) suppress the immune system of poultry making them more susceptible to diseases; (e) disrupt bone development causing a rachitic type problem and (f) can cause nutritional problems through its effect on nutrient absorption and metabolism.
Aflatoxin inhibits fat digestion with a consequent streatorrhoea by decreasing enzymes and bile acids resulting into high faecal fat and liver fat content. Aflatoxin causes reduction in nutrient retention, changes in haematological values and bio-chemical parameters. This toxin causes low or heavy mortality depending upon level and duration of intake of contaminated feed. Reduction in size of bursa of Fabricious is observed in growing chicks during aflatoxicosis.
A is primarily a nephrotoxin in poultry but it does have some secondary hepatotoxicity. The major diagnostic lesion of this mycotoxin is pale and enlarged kidneys. Ochratoxin like aflatoxin can affect poultry in number of ways: it i) depresses growth of poultry; ii) acts as an immuno-suppressant making birds more susceptible to diseases and brushing and iii) can affect nutrient absorption and metabolism. It is important to note that ochratoxin is three times more toxic than aflatoxins to broiler chicken. This toxin is produced by certain Pencillium (P.Verrucosum) and Aspergillus (A.Ochraceus and A.alutaceus) species. It has been implicated in total human disease Balkan Endemic Nephropathy.
T-2 TOXIN:
is produced by fungus Fusarium tricincutum. T-2 toxin is another mycotoxin that can produce severe adverse effects on broiler chicken. T-2 toxin is a radiomimetic toxin, which means that the toxicity of T-2 toxin is very similar to the effects of radiation. The principle presumptive lesion caused by T-2 toxin is a crusty lesion in the mouth of poultry on lower and upper mandible. T-2 toxin can limit poultry production by a number of methods: 1) decreasing body weight, 2) acting as immuno-suppressant and 3) altering nutrient absorption and causing nutritional disease.
Rubratoxin B causes reduction in growth, atrophy of bursa hypertrophy of liver. Tremortirn A affects central nervous system and causes tremors. One of the symptoms of citrinin toxicity in poultry is a dramatic increase in the amount of water consumed and excreted which helps in diagnosing its toxicosis.
There are a number of ways in which feeds can become multiple mycotoxin contaminated. Several analytical laboratories have found that most mycotoxin contaminated samples contain more than just a single mycotoxin. When aflatoxin and Ochratoxin are co-contaminants of poultry feed, these interact in a synergistic manner. During dual exposure of these toxins, ochratoxin prevents the major effect of aflatoxin (i.e. fatty, yellow, enlarged and friable liver). This confuses the ability to diagnose aflatoxicosis in the field. The target organ in this interaction appears to be the kidney. Citrinin is a nephrotoxin similar to ochratoxin and is produced by some of the fungi that also produce ochratoxin. The interaction is characterized as antagonistic. During co-toxicity ochratoxin prevents the very important diagnostic index of citrinin (increase in the amount of water consumption and excretion) which would make it very difficult to diagnose citrinin in the field based upon symptoms, if ochratoxin was also a contaminant. Aflatoxin and T2 toxin combination is like interaction between aflatoxin and ochratoxin and exhibit synergistic toxicity. The tolerance level of aflatoxin B1, dietary additive to protect broilers from aflatoxin B1 toxicity and physico- chemical treatments for inactivation of preformed aflatoxin B1 in feeds
Tolerance levels (ppb) of dietary aflatoxin in different poultry birds.
Pure bred broiler chicks – 200
White Leghorn chicks – 150
Quail chicks – 300
Quail layers – 300
Guinea fowl keets – 1500
Layers – 600
Dietary additives and their dietary inclusion levels for protection to broilers against dietary aflatoxins
Detoxifying agents g/qtl. Feed
Activated charcoal 100 – 200
Hydrated sodium calcium aluminosilicate (HSCAS) 100 – 200
Esterified glucomannan (EGM) 50 – 100
Herbal mixture (Acacia catechu. 25%, Phyllanthus niruri, 400%, Andrographis paniculata, 25%, base 10%) 50 – 75
Butylated hydroxyanisole 50 – 100
Dl-methionine* 100 – 200
Selenium** 0.200 – 0.300
Butylated hydroxy toluene* 50 -150
L-lysine HCI 150
Water soluble vitamins* Double of the requirements
Increase the dietary protein level Upto 26 to 28%
*Growth sparing effect.
**Alleviation of toxicity due to low levels of aflatoxins; growth and mortality effects at higher levels of aflatoxins.
Table 9. The physico-chemical treatments for inactivation of preformed aflatoxins in contaminated maize and groundnut cake.
i. Raising the moisture level upto 20%. Autoclaving at 5 PSI for one hour followed by drying in an oven at 80°C.
ii. Adding sodium hydroxide (15 g/kg) and mixing. Raising the moisture content upto 20%, autoclaving at 5 PSI for one hour and drying in an oven.
iii. Agitation of one kilogram of feedstuff with 20 g Ca(OH)2 followed by addition and mixing of formaldehyde to raise the moisture content upto 15%. Autoclaving at 15 PSI for an hour and drying.
iv. Addition of liquor ammonia to yield 6% concentration. Raising of moisture content upto 20%. Storing airtight for 20 days. Heating at 35°C and drying in an oven.
Pesticides and other industrial chemicals:
Pesticide/insecticide residues also pose a health hazard to livestock including poultry. These compounds of diverse chemical nature may be categorized into (a) the chlorinated hydrocarbon i.e. organochlorine (OC), such as DDT, BHC, aldrin, endrin, dieldrin, methoxychlor, chlordane, texaphene, mirex, etc., which are of persistent nature but harmless, if used correctly; (b) the organophosphorus compounds (OP), such as parathion, malathion, sumithion, dimelthoate, diazinon, etc.; (c) the carbonate compounds, such as carbaryl, pyrolan, etc. and (d) the synthetic pyrethroids, such as permehrin, cypermethrin, deltamehrin, allethrin, fenvalerate, etc.
The organochlorine insecticides are much less toxic and yet are dangerous because of their persistence and cumulative character in the body tissues. The poultry and other livestock products, viz. milk, meat, eggs obtained from the animals and birds, which are being exposed to the residues of such persistent insecticides, could be also harmful for human consumers.
Acute oral LD50 of malathion has been reported to be 524.80 mg/kg body weight for desi poultry birds. Exposure to some organophosphorus esters causes organophosphorus -induced delayed neurotoxicity (OPIDN) in adult poultry characterized by degeneration of axons and followed by myelin in the peripheral and central nervous systems.
Dr Surinder khanna, Poultry consultant.
Reference-On request
