By Joshua Kato
It was about 1:00pm on June 7th when Jordan Mulindwa parked his Isuzu truck at Kassanda agro-dealers stores in Kasanda. This was perhaps the hundredth time he had done so. Every time he came here, he loaded maize in the afternoon, before setting off the next day on that long journey to Southern Sudan. This maize is mainly produced by smallholder farmers in greater Mubende.
“They loaded seven tonnes of maize,” he says. Twelve hours later, he was in South Sudan. By this time, there were over 90 trucks across the border, all carrying maize. Some had come from areas of Gulu, Amuru and Nwoya, Busoga, Luwero, Mubende,Kiboga and Kyankwanzi districts.
“These Sudanese officials were carrying out more stringent checks than usual,” Mulindwa says.
What started as a ‘simple’ quality check dragged on for weeks! Between May and July 2023, 90 of 450 trucks transporting maize from Uganda to South Sudan were impounded by the South Sudan National Bureau of Standards at the Nimule-Elegu border post on allegations that the quality of some of the maize was poor.
Huge losses
The trucks were loaded with maize grain, maize flour and wheat on allegations of failing to pass the test for contamination with aflatoxin, they were retained at the border. Richard Sserwadda, the chairperson of the National Millers Association, said the cargo is worth over sh8b. Results from a test done by the Uganda National Bureau of Standards (UNBS) on the disputed loaded grain found out that at least 50% was infected by aflatoxin, hence not fit for human consumption.
The infected food was due for destruction by the time of filing this story, hence making big losses for the traders.
According to Dr Achileo Kaaya, from Makerere University and who has done extensive research on the effects of poor postharvest handling on cereals and grains, aflatoxins are poisonous by-products of the growth of the moulds Aspergillus flavus and Aspergillus parasiticus on cereals and grains.
“During that one month, I would have made two more trips here or elsewhere,” Mulindwa says. He makes a profit of sh2m from each trip,” Mulindwa says.
South Sudan (SS) was the second country to suspend importation of Ugandan maize, after Kenya.
According to the Grain Council of Uganda, on average, Uganda loses an estimated $38m annually in export opportunities due to aflatoxins. For instance, in 2018, Kenya rejected the importation of 600,000tonnes of maize from Uganda (equivalent to $ 126m) owing to poor quality and especially aflatoxin contamination.
Aflatoxins are toxins that are produced by the fungus Aspergillus flavus on grain.
“They are a highly toxic and carcinogenic compounds that are linked to ailments such as liver cancer. In Uganda, an estimated 3,700 liver cancer cases reported per year are attributed to aflatoxin,” the Uganda Grain Council says. This health burden translates to between US$144.3m and sh577.2m, or 0.53–2.14% of Uganda’s total GDP. According to experts, not even cooking or roasting of the produce can destroy the toxins. Besides, these toxins are not visible, tasteless and odourless, making it difficult to detect their presence in food. They are detected only after testing the grain.
Aflatoxins are of economic and health importance because of their ability to contaminate human food and animal feeds, in particular cereals, nuts and oilseeds, cheese, almonds, figs and spices. “There are so many cancers for example stomach cancers, now developing in the country and these are linked to the foods that people consume. These toxins may be one of the causes,” Kaaya said.
Widespread
Majority of maize in Uganda is produced by small holder farmers, who sell the dried grain to middlemen. It is these that sell to the trucks that carry it to Sudan. In Kasanda, a leading maize producing part of greater Mubende, Sarah Byeyitsi has been growing maize for over 10 years now. “I have 5 acres of land out of my 10acres dedicated to maize every season,” she says. But like most farmers around her, Byeyitsi dried the grain in a rudimentary way. “I use tarpaulins spread on the ground. When it threatens to rain, I run and remove them,” she says. She admits that on a few occasions, her maize has been hit by rain. “Of course, we dried it further and sold it,” she says.
However, according to experts, one of the causes of aflatoxin in maize is higher moisture. “Do not allow rain or water to get in contact with your grain. Even if you dry it later, the damage may have been done,” Dr Kaaya says.
An earlier survey done in 2018 by Dr Swidiq Muherwa, 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 40.5 ppb, 42.8 ppb, 67.5 ppb, 6.4 ppb. Ppb (parts per billion) is a unit of measure for minute substances that are so small to be expressed in grammes. For example, according to Mugerwa, 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 in the East African Community has set a limit of 10 parts per billion 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 European Union (EU) having the most stringent standards, at 4ppb.
Affects livestock adversely
According to Mugerwa, ingestion of feed contaminated with aflatoxins not only undermines animal performance and productivity by retarding growth, but also present huge health risks to consumers of animal tissues and products. While humans can acquire the toxins by consuming foods like maize, sorghum etc affected by the toxins, they can also acquire the same by eating meat or products from affected livestock. The International Agency for Research on Cancer 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 than recommended. Most of the time, the livestock are given the poorest feeds after humans make their pick,” 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 pointed out that 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 utilisation 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%,” Mugerwa explained
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 vaccinate chicken from diseases like Newcastle, there is no effect because of the toxins affect the effectiveness of the vaccines in the animal cells,” Mugerwa says.
Allan Iga, a livestock nutritionist advises livestock farmers to use toxic binders in their feeds to reduce the impact of the toxins in maize bran. “Farmers must buy only that bran that is clean, without any blackish substances, but they must also add a toxic binder in the feeds to tame any possible toxins. The product is a blend of sodium bentonite, that is processed and mixed with feeds to stop the effect of the toxins. These can be bought from most agri-input stores.
Fighting aflatoxins
Fighting aflatoxin starts at the farm level, according to experts. “Farmers must make sure that they deal with pests like maize borers because when they eat through the maize, they can create an environment for aflatoxin,” says Dr Christine Nambajjwe. She explains that farmers must also harvest grain at the right time and dry it without exposing it to water. “The biggest threat to harvest grain is getting in contact with water,” she says.
Additionally, government through NARO is promoting an application that can reduce aflatoxin at the farm level.
Dr. George Mahuku, from the International Institute of Tropical Agriculture (IITA) explains that this is a nature-based solution to minimize aflatoxin contamination in the crop harvest.
“From our research, contamination starts from the field contrary to what many have been saying that it starts at post-harvest level. This therefore means that we need to deal with it right from the field.
He explains that in the field there are different types of fungi belonging to the aspergillus flavus. There are those that cause aflatoxigenic and those that don’t produce the toxin.
“So, we go to the environment and pick those that don’t produce the toxins since we realized that these thrive better in the environment. So, we characterize these in the laboratory to make sure that they don’t produce the toxin or that they don’t belong to the group that produces toxins such that when they are put back to the environment there is no chance that they will mix or exchange genetics with the toxic producers,” he says.
“It is a biological control process that utilizes fungi that don’t produce toxic to out compete or displace toxin producers. Once the toxin producers are displaced, you don’t get aflatoxin,” he explains.
More measures
A technology that can wipe aflatoxin from grains has been introduced in Uganda. The TOXI-SCRUB has been introduced by Peer Hansen, from EYE-GRAIN Aps through Grain and TOXIN Solution, a local company managed by Kim Johansen.
“It helps remove all aflatoxin and mycotoxins in maize and other grain such as sorghum, wheat and any type of nuts and beans,” Hansen said. This is welcome news given the fact that Ugandan maize was recently suspended from being exported to Kenya over aflatoxins.
“The Danish technology uses ozonation process to remove the toxins,” Hansen says. Ozonation is a green technology that is friendly to humans, animals and the environment. Hansen explains that the technology is suitable for large scale grain stores because it can clean 30tonnes of grain per hour. “When the grains pass through the system, they become de-toxified,” Hansen, who has the patent for the technology says. A unit costs about US$300,000 (sh1.1bn). “A country like Uganda needs about 10 of these systems, given the level of grain production,” Hansen says.
Tips for farmers/traders–
-Thresh or shell your crops in a proper way. It is important for farmers to minimize damage to grains during threshing/shelling as damaged grain is much more susceptible to attack by insects and fungi in storage. Consequently, techniques that crush and damage grains such as beating with sticks are not recommended, except in commodities where beating poses no significant damage.
-Note that drying is the most important element of postharvest handling, so ensure that you do it properly. This includes drying on mats, plastic sheets or tarpaulin, raised stands, solar driers and for larger grain dealers there are mechanical driers.
-Ensure that the garden is clean, with no weeds after planting. It is advisable to weed two to three times without injuring the crop especially when the pods have started growing. Weeds host pests that may attack and damage the crops.
-Farmers should harvest crops and plants in time because delaying harvesting leads to the sprouting of already mature seed, creating an entry of the fungus.
-After harvesting, ensure that they dry immediately and properly. Moisture content for most grains is between 9%-14%. There are cheap grain moisture gauges that a farmer can use.
-Do not dry good grain mixed with bad grain. Bad grain carries pests that may infect the good one.
-Do not allow the produce to be wetted and soaked by rain, if it happens make sure it is dried as soon as possible again.
-At harvesting level, it is advisable to keep the grain in jute bags as these are aerated or clean plastic bags. There are also grain silos that can take 200-500kg.
When stacking or arranging the bags in the store, they should not be squeezed or placed on the bare ground. From the ground they pick up moisture which leads to the growth of mould.
