Nutritionist > Pig

Aflatoxins
Aflatoxins are produced mainly by Aspergillus flavus and Aspergillus parasitium. They are of concern in warm and humid climatic conditions. Although aflatoxins are not considered to be a major problem in cold or more temperate regions, caution must be exercised in colder climates when using feedstuffs imported from warm and humid countries.

There is a variety of aflatoxins (B 1, B 2, G 1, G 2, M 1, M 2) produced by Aspergillus flavus. Relative to the temperature, Aspergillus flavus easily produces aflatoxins at about 25°C, and under 10°C the toxin production has never been demonstrated. Grain moisture levels of 22% to 26% provide ideal conditions for producing aflatoxins in a variety of grains, including corn, wheat, barley, and oats.

Aflatoxins have been shown to be carcinogenic, and therefore there are concerns about the mycotoxin entering the human food chain. For pigs, they are the most acutely toxic of all mycotoxins, causing extensive liver pathology. There is also concern about residues of aflatoxin and metabolites in food, because of the well-documented carcinogenic nature of these compounds. Therefore, many countries have set upper limits for aflatoxins in feeds (See regulations page on this site for more details). Grains containing aflatoxin levels in excess of 20 ppb cannot be used for human consumption and animal feeds, and should not be fed to young animals.

At low levels (20 - 200 ppb), aflatoxin decreases performance and well-being. Feed intake is commonly reduced, resulting in depressed growth rate, while immune function is suppressed. At high levels (1000 ppb +), death may occur.

Clinical effects:
These include reduced growth rate and feed efficiency and, at extreme levels, liver damage, such as fatty changes, lobular necrosis, with an increase in basophilic cells at the periphery of the lobule and bile duct. In extreme chronic cases cirrhosis and death may occur.

Indicators of liver damage are elevated serum activities of gamma-glutamyltransferase (GGT) and alkaline phosphatase, as well as elevated levels of serum albumin and total protein.

Feeding diets contaminated with aflatoxin may exacerbate vitamin A and vitamin E deficiency in pigs, as well as reduce the immune function. This renders the animal more susceptible to any concurrent disease, such as PRRS, PWMS, viral influenza and mycoplasma pneumonia and secondary infections are common.

Although low concentrations of aflatoxins are tolerated, the combined adverse effects of aflatoxin on hepatic metabolism, protein synthesis and immune status reduce swine reproductive efficiency. Increasing the level of aflatoxin B2 to 800 microgram/kg of feed resulted in fewer piglets born alive and weaned [Smith, T.K., Diaz, G. and Swamy, H.V.L.N. (2005). Recent Advances in understanding mycotoxicoses in swine. In: 'Manipulating Pig Production X. Proceedings of the Tenth Biennial Conference of the Australian Pig Swine Association (APSA)'. Edited by J.E. Paterson; pp 236-247. APSA, Werribee, Australia.]. Indeed, the effects of different aflatoxins on swine reproduction seem to be cumulative:

Clinical signs of aflatoxin toxicosis include:

• Reduced feed intake
• Reduced growth rate
• Poor feed conversion efficiency
• Lower sow reproductive performance
• Reduced lipid digestion
• Altered kidney function
• Liver damage:
• elevated y-glutamyltransferase
• elevated serum alkaline phosphatase
• reduced serum albumin and total protein concentration
• Reduced serum retinol and tocophenol concentration
• Vitamin A and E deficiency
• Reduced immuno competence = more susceptible to disease