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Potential for Feed acidifiers to create a safer food chain whilst being catalysts for growth of the Global Economy. – Tichaona Revesai


Tichaona Revesai (MBA, MSc)

Chief Value Stream Leader – Bidco Animal Feeds Division, Kenya

Increasing global Antimicrobial Resistance (AMR) is a major threat to human and animal health. It has now endangered modern human and veterinary medicine and undermined the safety of our food and environment. Overuse of antibiotics in humans and animals has caused the pace of anti- microbial resistance to quicken. A 2015 study from the Washington DC-based Center for Disease Dynamics found that global antibiotic use had risen by 30 per cent between 2000 and 2010. This has contributed to a situation where the emergence of bacterial resistance has outpaced antibiotic discovery. This is reflected in the high AMR related death toll. Each day an estimated 1,900 people around the world die from infections that are resistant to antibiotics: that is 700,000 people every year. As a result, annual global GDP could be reduced by between 2 per cent and 3.5 per cent by 2050 if nothing is done, equal to $60tn-$100tn of cumulative economic output being lost (with Africa leading the pack- 20% projected reduction in GDP) (KPMG). By the middle of the century, according to the UK’s 2016 Review on Antimicrobial Resistance (AMR) — more people will die due to antibiotic resistance than the number of people who will die of cancer this year.

Europe responded to the rising AMR by imposing a blanket ban of antibiotic growth promoters (AGPs) in 2006. However, in countries like Nigeria, Zimbabwe and Malawi, and many developing countries, the risk appears particularly higher due to weak or inadequate legislation, regulatory surveillance and monitoring systems on the use of antimicrobials, and the prevention and control of Antimicrobial Resistance.

In South Africa antibiotics resistance in human medicine, is now reaching alarming levels although experts link this more to the oversubscription of prescription antimicrobials by doctors and some studies also implicate the overuse of antibiotics in food animals. The mcr-1 colistin resistance gene has been reported among Escherichia coli in both clinical and poultry samples in two provinces in South Africa. This is a threat to all Africa and Europe as many patients from several countries in these continents seek health care in South Africa (Sekyere, 2016). Resistance to last- resort antibiotics, such as carbapenems, tigecycline, and colistin, is increasing among Gram- negative bacteria in South Africa, restricting infection management options for clinicians and posing a threat to food safety. A total of 3544 avian pathogenic Escherichia coli strains isolated

from commercial broilers in South Africa between 2009 and 2015 were tested for susceptibility against eight classes of antimicrobials. Time series analyses were conducted to assess seasonal and general trends in antibiotic resistance. Seasonal trends were seen in the tetracyclines, with peaks of resistance in the winter months when respiratory diseases are at their worst. Resistance to quinolones peaked in 2012 after which there was an overall decreasing trend in resistance. Colistin resistance increased gradually from 2009 with a drastic rise to 12.08% in 2015, but its use in feed was stopped in 2016. Florfenicol also showed a sharp increase in resistance from 2.36% in 2009 to 6.63% in 2015. Resistance to trimethoprim-sulphadiazine decreased sharply by the end of 2015, as did spectinomycin and fosfomycin and amoxicillin. The overall prevalence of multidrug resistance (MDR) was 80.6 (95% confidence interval, 0.743-0.819), but the years 2013, 2014, and 2015 showed a significantly lower level of MDR compared with 2009 (www.ncbi.nlm.nih.gov, 2019).


There are conflicting reports regarding the ratio of use of antimicrobials used in animals compared to humans. In South Africa, the ratio of use of antimicrobials was reported to be less in animals compared to humans. Import data for antimicrobials between 2014 and 2015 estimates procurement for animal health at 23-36% and for human use at 64-77%. Humans consume most penicillins and streptomycins. This ratio of animal to human use is in contrast, to reports from the United States of America (USA), China and India where animal consumption is the far larger proportion (www.nicd.co.za, 2019). This author believes that the ratio of usage is not related to the amount of antibiotics imported but the metabolic usage rate, how much drugs are consumed per kg of poultry produced and how much drugs are used per kg of human weight. In addition, usage in animals may be less because of higher human population density versus kilograms of livestock and poultry reared per square meter but this does not make the rising cross resistance caused by AGPs use in poultry and livestock a no concern issue.

From 2014 to 2015 it appears that the predominant antibiotic group used in animal health are growth promoters (62%), followed by tetracyclines (17%) and macrolides (11%). The growth promoter group includes antibiotics not used in human health such as ionophores, flavophospholipol (flavomycin), olaquindox, zinc bacitracin and tylosin.

Estimated consumption by animals of tetracyclines makes up about 27% of total antimicrobial sales, compared to the OIE reported 63% for most African countries over the same period. This possibly demonstrates that South Africa’s farming practices vary from those of other African countries.

Antimicrobial residues in meat products have been detected in 2.08% of samples analysed through the National Chemical Residue Monitoring Program, which includes penicillins, tetracyclines, sulphonamides and macrolides. This program monitors residues in meat for local and export markets.


From the above statements the risk of spreading antimicrobial resistance from food animals to humans appears to be very high in South Africa which poses a serious threat to human health. This situation, leaves, the poultry and swine industries not only in other countries around the world but also South Africa desperately needing more sustainable and economical feed additives which could elicit growth promotion without selecting for microbial resistance, causing environmental pollution, gut microbial imbalance and causing cytotoxicity and acceptable to the consumers.

The responses of South Africa and other African countries, to AGP linked AMR has been totally different from those of European countries, with most African countries not acting swiftly against AGP use in animal feed, although it seems like more countries are now taking action. Of note,

Kenya has made commentable progress in discouraging the use of AGPs in animal feed through various lobby groups and Zinc Bacitracin is now completely out of the Kenyan market as of April 2021. In Malawi at least 80% of the chickens being consumed in that country are fed feed formulated with AGPs. In Tanzania KFC in line with its corporate social responsibility policy has been leading the elimination of AGP in animal feed by making it a requirement that their chicken meat suppliers do not use these in feed.

The feed industry in the developed world responded to the ban on AGPs by looking for safer alternatives such as organic acids, processed animal proteins, syn-biotics (pro and prebiotics) and phytogenics.

Due to the wide adoption of organic acids as alternatives to anti-biotics, this author has decided to look, into their potential in substituting antibiotics in feed and share some insights on their feasibility to impact economic transformation by minimizing AMR.

To begin with we need to first understand what organic acids are and their mode of action on certain pathogens in order are to assess their de novo functionality. Once that understanding is inculcated, we can then look at the theoretical design models of the products, how they can be maneuvered in practice to produce desired impact on gut health and immunomodulation and at what rates. It will also help nutritionists, veterinarians and researcher to evaluate how they function in practice and evaluate their efficiency and gaps for improvement. This article will not go into all these details but in other articles more to follow will be discussed.

So back to the starting point, what are organic acids?

Organic acids can be categorized as feed and gut acidifiers, ranging from lactate, propionate to formate. These are a group of weak acids, both in powder form (salt) and liquid which have antimicrobial properties, mould inhibitory, toxin binding and grain and food preservatory properties. They boost the immune system of poultry and pigs by suppressing harmful pathogens in the digestive system, which cause disease, high mortality, poor growth, digestion and also compete for nutrients with the animal.

These acidifiers have a positive immunomodulation effect on the animal; whilst they improve the growth of intestinal villi thus increase surface area for nutrient absorption through the small intestine. In the crop the pH is normally above 6 and at that pH most of the harmful bacteria like Salmonella species thrive and multiply, negatively affecting the animal. After ingestion of feed, it takes about 6 hours for the pH of the crop to come down. With addition of organic acids in feed the pH of the crop drops to 4 within 30 minutes, making enzyme pepsinogen activated to pepsin faster, improving rate and extend of digestion. At that pH most harmful gram –ve and gram +ve bacteria are unable to grow. When added as salt the organic acids will be in partially dissociated form. The undissociated form has ability to enter bacteria and dissociate in-side the bacteria, making the pH of the bacteria unfavourable. The bacterium spends a lot of energy trying to eliminate/export the organic acid’s hydrogen cations, thus slowing down its rate of multiplication.

The overall results will be better health, reduced mortality, better feed conversion efficiency and growth rate and better carcass quality all without any residues in the meat which affect consumer health, like what happens with antibiotics.

Overall, the benefits of using organic acids in feed to the farmers, meat consumer and broader society can be summarized as below:

Ability to produce safer food for local consumers (reduce death rate of people dying from antimicrobial resistance). This is the main societal comparative advantage. With increasing recognition of the contribution of antibiotic growth promoters to death related antibiotic resistance and consumer demand for antibiotic free food, organic acid suppliers might have an advantage over competitors who sell antibiotic growth promoters. This is valid so long animal performance is not impaired.

In the subsequent publications we will delve deeper in order into some organic acid products that are currently on the market what has been their success rates in substituting antibiotics and improving the safety of the feed food chain. We thus will be answering the following question, how does 100% substation of antibiotics for organic acids affect animal performance, what is the effect of combining organic acids with other non-antibiotic additives on animal performance and feeding economics. In addition, another important question that needs to be answered is has the withdrawal of antibiotic growth promoters resulted in an animal health crisis and if yes what is the impact of the animal performance loss to the global economy? Especially, the author will present a literature review of some critical studies that have been carried out in Europe and certain countries in Africa in order to provide objective answers to these questions. For now, through this introductory article, it is sufficient to say these products hold enormous potential to substitute antibiotics in feed and thus reduce antimicrobial resistance, leading to reduced deaths caused by AMR and significantly improving the growth of the global economy.