Mycotoxins are the harmful substances produced by certain species of fungi. Many species of fungi may produce more than one type of toxin. The more common types of mycotoxins occurring in foods and animal feeds include aflatoxin B1, B2, G1, G2, ochratoxins, fumonisin and zearalenone. Mycotoxins have got attention as they are toxic to human and animal health. The most acutely toxic is aflatoxin B1 and is responsible for liver cancer in humans. Dairy animals after consuming feed affected with aflatoxin B1 (AFB1), excrete the by-product aflatoxin M1 (AFM1) in their milk that causes cancer. The extent of mycotoxin toxicity in animals and humans exposed through feed intake depends upon various factors like species, metabolism, mechanisms of action, and defence system of the individual.

In earlier research on aflatoxins, acute toxicity patterns in different species were studied. The dose of toxin at which 50% of sheep, rats and ducklings die is 500 mg/kg, 1 mg/kg and 0.4 mg/kg respectively. The maximum permissible levels for aflatoxin B1 and aflatoxin M1 in foods and animal feeds have been established by many countries in the world. In dairy animals feed the level of aflatoxin B1 should not exceed the concentration of 20 µg/kg. The permissible level of aflatoxin M1 in animals’ milk ranges from 0.05µg/kg to 0.500 µg/kg.

Goat farming in Pakistan has become an indispensable part of livestock industry. Many people from all the four provinces of the country are involved in this profitable business as a source of their income. Aflatoxin B1 contamination status of dairy goats feed cotton seed cake, wanda, wheat bran and homemade concentrate mixture was investigated by researchers in district Lahore. Aflatoxin B1 was detected in 33 feed samples out of 40 thus with a percent contamination rate of 83%. Maximum level of aflatoxin B1 was detected in cotton seed cake and minimum level was detected in wheat bran.

Beetal is the best dairy goats’ breed of Pakistan. Effects of dietary aflatoxin B1 (AFB1) on health status of lactating beetal goats and its transfer from feed into milk as by-product aflatoxin M1 (AFM1) were recently investigated. Aflatoxin M1 was detected in all milk samples with concentration beyond permissible level which is 0.05 µg/kg (European communities). Somatic cell count of milk, total bacterial count of milk, and liver enzymes aspartate aminotransferase (AST) and alanine aminotransferase (ALT) levels increased with consumption of dietary aflatoxin B1 that shows that liver and udder health is badly affected.

The transfer of aflatoxins from feed into milk can be reduced by using various chemical, physical and biological methods. The physical way of removing mycotoxins from feed is the addition of different adsorbents (binders) in animals contaminated feed.

In recent study different mycotoxin adsorbents were used to decontaminate animal feed and investigate their beneficial effects on health status and milk quality of beetal goats. It was observed that adsorbents significantly decreased the excretion of aflatoxin M1 in goat milk, but milk quality and liver functions were not improved during one week experimental period.

It can be concluded that cotton seed cake usually has high amount of aflatoxin B1, aflatoxin B1 has injurious effects on health status and milk quality of dairy animals, and excretion of aflatoxin M1 in milk can be significantly reduced by using mycotoxin binders in animal feeds.

In light of these facts, it is recommended that cotton seed cake feeding to dairy animals may be replaced by another type of concentrate feed that is less affected by aflatoxins. Mycotoxin binders may be incorporated in daily ration of lactating animals to control the excretion of aflatoxin in milk. In order to ensure safe milk supply, milk testing for aflatoxins may be made mandatory for all dairy producers by government agencies.

- The writers Dr Aneela Zameer Durrani and Dr Haq Aman Ullah are chairperson of department of clinical medicine and surgery at UVAS, Lahore, and professor at Agriculture University, Peshawar, respectively.