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How Aflatoxins Affect Livestock

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Charles Mulindwa’s three-month-old piglets developed a red enlarged vulva. When he contacted a veterinary officer, it was discovered that the pigs were suffering from a disease called mycotoxicosis, which is caused by high levels of mycotoxins in feeds. Mycotoxins are caused by aflatoxins that got embed in feeds due to poor post-harvest handling of grains. This is happening to many piggeries across the country although farmers are not aware of the causes.

Last week, the Grain Council of Uganda issued a statement warning grain producers to watch out for the increasing rains, with flooding in some areas as they dry their grains.

According to the statement by the Grain Council of Uganda, aflatoxin is a poison produced by a fungus, aspegrillus flavus. The fungus resides in soil and decaying organic matter in the field. It contaminates many crops, but the most susceptible are maize, sorghum and groundnuts. Aflatoxins are also found in livestock products such as milk, eggs and meat when livestock are fed on contaminated feed.

It can also be found in a mother’s breastmilk if they have consumed food contaminated with aflatoxin and they are able to pass it on to their infants when they breast feed. Early this year, Uganda’s maize exports to Kenya were suspended due to prevalence of aflatoxin in the grain.

“Make sure that you do not expose your grain to rain under any circumstances because it may get infected by mould that leads to development of aflatoxin,” the statement read. Uganda produces about 6 million tonnes of grains per year.

How aflatoxins are spread

Dr Archilleo Kaaya from Makerere University, who has done research about aflatoxins for many years in Uganda and Africa, says the situation is bad and affects both livestock and humans.  

Aflatoxins can attack and contaminate grain before harvest or during storage. Host crops which include maize, barley, sorghum, soya and groundnuts, are particularly common to infection by fungi following prolonged exposure to a high-humidity environment or damage from poor handling conditions such as drought.

Feeds infected

Results from a comprehensive animal feed quality survey processed in Uganda in 2018 by the National Agricultural Research Organisation (NARO) indicated massive infestation of the feeds with toxins.

Dr Godfrey Asea, the NARO boss, said 256 pre-harvest samples were collected from 23 major maize-growing zones.

“Results indicated that there were between 03,760ppb in the sample.  This was so high given the fact that the recommended volume is 0-20ppb,” he said.

An earlier survey done by Dr Swidiq Mugerwa, the director of research at the National Livestock Resources Research Institute (NaLIRRI) revealed that the mean aflatoxin concentration in broiler starter, broiler finisher, layer mash and dairy meal was 40.5ppb, 42.8ppb, 67.5ppb, 6.4ppb, respectively.

Ppb (parts per billion) is a unit of measure for minute substances that are so small to be expressed in grams. For example, the recommended aflatoxin concentration in animal feed is 20 ppb. This means that in every one billion units of animal feed, there should be not more than 20 units/parts of aflatoxin.  

The Uganda National Bureau for Standards (UNBS), in collaboration with other bureaus of standards from the East African Community has set a limit of 10ppb for all foods and feeds, but only currently certifies products intended for export. Other countries have different maximum tolerable levels of aflatoxin contamination with the EU having the most stringent standards, at 4ppb.  However, the UNBS says it is not so easy to monitor the levels of aflatoxins in Uganda because most of the produce is traded informally.

Mugerwa says ingestion of feed contaminated with aflatoxins not only undermines animal performance and productivity, but also present huge health risks to consumers of animal tissues and products. While humans can acquire the toxins by consuming foods like maize and sorghum affected by the toxins, they can also acquire the same by eating meat or products from affected livestock. The International Agency for Research ranks aflatoxin as Group 1 possible cancer causers. In children, they reduce growth, leading to stunting and kwashiorkor.

“Livestock feeds have a higher concentration of toxins because most of the time, we save the poorest feeds for livestock,” Mugerwa says. For example, maize bran, which is the base for mixing livestock feeds comes from the skin of the grain, which at the same time is more vulnerable to mould.  

Mugerwa says despite their importance in sustaining food and nutritional security, economic development and poverty eradication, the productivity and profitability of intensive dairy and poultry industries in Uganda is undermined by the detrimental effects of aflatoxicosis. Aflatoxicosis is the syndrome resulting from ingestion of feeds contaminated with aflatoxins.

Ingestion of feeds by animals containing such alarming levels of aflatoxins is associated with growth depression owing to aflatoxin-induced decline in feed intake, impaired nutrient utilization and decline in feed quality. It is estimated that with each mg/kg increase of aflatoxins in the diet, the growth rate for broiler birds would be depressed by at least 5%. In laying birds, aflatoxicosis reduces egg production and egg size by 10 and 5% respectively, in addition to impairing semen quality.

Additionally, aflatoxins are immune-suppressants and aflatoxicosis has been noted to escalate the susceptibility of birds to infectious diseases such as Newcastle disease.

“Because of these toxins, when you immunise chicken against diseases such as Newcastle, there is no effect because of the toxins,” Mugerwa says.

Mugerwa says Aflasafe, an application farmers can take to reduce aflatoxin infections on farms, has been recently introduced. The product has already been patented.

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