Mycotoxins are a family of toxins produced by certain fungi. There are three main types of mycotoxins that produce toxins are Aspergillus, Fusarium, and Penicillium, which are abundant in warm and humid regions of the world. Aspergillus produce toxin which are more abundant and known as Aflatoxin. These fungi can contaminate crops in the field, at harvest, and during storage. According to the Food and Agriculture Organization (FAO), one forth of the world’s crop is affected by aflatoxins. Aflatoxins are a group of hepatotoxic, carcinogenic and immunosuppressive fungal metabolites. International Agency for Research on Cancer has classified aflatoxins B1, B2, G1, G2 and M1 as group 1 carcinogen. Aflatoxin B1 is the most toxic compound and it is one of the biosynthetic precursors of the other aflatoxins.
When lactating mammals such as cows, sheep and goat are fed with AFB1 contaminated feed, the ingested AFB1 is converted to AFM1 by hydroxylation at the tertiary carbon of the difuran ring system, metabolized by cytochrome P450 enzyme system in the liver. About 0.30 to 6.2% of AFB1 in animal feed is transformed to AFM1 in milk. The transformation rate may vary from animal to animal. The AFM1 starts appearing in milk approximately after 12 to 24 h of the first AFB1 ingestion.
Aflatoxins are a worldwide threat to public health and economy and therefore, extensive surveillance on the levels of aflatoxins B1, B2, G1, G2 and M1 has been conducted throughout the world including developing countries like India and Pakistan. The presence of aflatoxin M1 in milk and dairy products makes it a particular risk for humans because these products are largely consumed by children including infants who are considered more susceptible to the adverse effects of AFM1. More than 60 countries have set maximum permissible level for AFM1 in milk.
Pakistan is the fifth largest milk producer in the world with an approximately 29 million tons annual production. Milk in Pakistan is mainly produced by small farmers at small scales. Feed storage conditions in small scale farms are often not satisfactory due to economic backwardness of the producers and would not reduce the occurrence of the mycotoxins in the feed or the milk. Most milk (70%) in Pakistan is produced by buffalo. About 98% of the milk is sold in raw form with only 2% going to processing. A significant portion of milk is converted into dairy products. Among the dairy based products, mithae is a popular traditional dessert in Pakistan. Different types of mithae such as burfi, ras gulla, laddu, chamcham are the essential element of many celebrations in Pakistan’s culture. Punjab is the major milk producing province (67% milk share of the total production) of Pakistan. Limited research in Pakistan has been carried out to estimate aflatoxin B1 in feed sources and aflatoxin M1 in milk from a few selected areas of Pakistan.
In 2015 a research study conducted in University of Veterinary and Animal Science Lahore to estimate the aflatoxin B1 contamination in animal feed sources and milk samples collected from the different area of Punjab Pakistan. Total 960 milk samples were collected from five regions of the Punjab province on monthly basis including all seasons. Interestingly findings unveiled that about 68.95% raw milk samples exceeded the United States permissible and Punjab Food Regulations (PFA) maximum residue limits (MRL 0.50 µg/L) while overall AFM1 level ranging from 0.300 to 1.000 µg/L. Raw milk AFM1 concentration was higher in winter season (0.875 µg/L) followed by autumn (0.751 µg/L), spring (0.654 µg/L) and summer (0.455 µg/L). Similarly 240 different feed samples were collected and evaluated for aflatoxin B1 levels. It is observed that cotton seed cake, corn, rice polish and bread pieces were the most significant contributors for aflatoxins contamination in feed and ultimately converted to milk.
Study urges food authorities and livestock departments of Pakistan to mobilize food safety laws in milk supply chain and initiate official regulations on control of AFB1 in animal feed sources. Government agencies should introduce subsidies programs to introduce good storage practices, pre- & post-harvest control measures, effective grain drying techniques and support to protect animal feed ingredients from weather hardships. Introduction of contamination free forage sources e.g. high yield green fodder verities, grasses, and silage making techniques could be a low hanging fruit in reduction of aflatoxin M1 in milk supply chain. Linkages between grain producers, feed manufacturer’s, dairy farmers, food and livestock departments is a dire need to reverse these increasing levels.