Introduction

In intensive poultry farming, there are several factors capable of affecting liver functionality, such as the presence of toxics and mycotoxins, different microorganisms, metabolic overload, etc. The liver is a multifunctional organ, essential for bird´s health and productivity, so it is important to prevent liver damage.

In African poultry, three main factors affecting liver are, on the one hand, the high prevalence of hepatotoxic mycotoxins, the continued use of antibiotic growth promoters (AGP), which metabolization ends up impairing liver functionality and the use of sorghum in the feed formula, due to the presence of anti-nutritional factors.

The addition of pronutrients in the diet, active molecules of botanical origin, improves intestinal and liver well-being, as well as restore liver functionality after exposure to a hepatotoxic challenge, ensuring the productive performance of birds.

At the same time, the addition in the diet of a mycotoxin binder, with a high binding percentage, allows to prevent the hepatotoxic effects of these secondary metabolites.

Importance of the liver in poultry production

The liver plays a key role in the productive performance of birds, since, among its multiple functions, are the synthesis of lipids and proteins, necessary to produce meat and eggs.

Its various functions include:

Detoxifying function

The liver is responsible for transforming all those toxic compounds present in the feed, as well as the toxic metabolites produced by the animal itself into more polar compounds, through conjugation, oxidation, reduction and hydrolysis processes, so that they are eliminated through the kidney.

Mycotoxins, chemicals, and drug degradation products, such as antibiotics, are particularly relevant within toxic compounds.

Metabolic and synthesis function

The liver plays an essential role in the metabolism of lipids, proteins, and carbohydrates. In birds, the liver is responsible for lipid synthesis, by converting glucose into triglycerides. At the same time, it produces the bile acids, necessary for fat emulsification in the intestine, an essential step for the digestion and absorption of fats.

In addition, the liver is responsible for the synthesis of the necessary proteins for growth and production of eggs. The liver also synthesizes the proteins needed for blood clotting, as well as immune effectors involved in the immune response.

Storage function

The liver works as a store, since it deposits nutrients such as glycogen and fat- soluble vitamins (Vit A, Vit D, Vit K and Vit E). [1]

Main livers challenges in African poultry

Due to its detoxifying function the liver is exposed to numerous toxic compounds and microorganisms that can affect its functionality.

As the liver is responsible for a large part of the protein synthesis, its affection results in a significant reduction in the bird´s productive performance.

The main liver challenges in African poultry are, on the one hand, the continued use of AGPs, which metabolization damages hepatocytes, the presence of hepatotoxic mycotoxins in feed and the use of sorghum in the feed formula, due to the presence of anti-nutritional factors.

Use of antibiotic growth promoters (AGPs)

The use of antibiotics as growth promoters in poultry was a common practice around the world to improve animal growth and productive profitability.

However, due to the emergence of antibiotic resistance and its relationship to the use of these chemotherapeutic substances at low doses and for prolonged times, many countries have banned the use of antibiotics for this purpose.

In Africa, the use of antibiotics as growth promoters remains a common practice, with macrolides and tetracyclines being the most frequently used antibiotics. [5]

The liver is responsible for metabolizing antibiotics into more soluble compounds, so that they can eventually be eliminated in the urine. The constant exposure of birds to these chemotherapeutic substances ends up irreversibly damaging the liver, affecting its normal physiological functioning and, consequently, the productive performance of the animal.

Presence of mycotoxins in feed

Mycotoxins are secondary metabolites produced by different types of fungi. High humidity and temperature conditions, such as those found on the African continent for much of the year, promote the development of these fungi and therefore the prevalence of mycotoxins in feed.

Fumonisin B1 and aflatoxins are the most prevalent mycotoxins in the African continent. The latest studies in Nigeria showed that fumonisins were present in 97% of the feed samples analyzed with an average of 1014 μg/kg and 100% of the maize samples analyzed. At the same time, the prevalence of aflatoxin B1 was 83% with an average contamination of 74 g/kg. [2]

Similar results have also been observed in Kenya, where studies have revealed the presence of fumonisins in 90% of the poultry feed samples analyzed, with contamination of between 32.4–144 μg/kg and presence of aflatoxins in 70% of feed samples. [3]

Studies in South Africa also indicate a high prevalence of fumonisins in feed, 100% of poultry feed samples analyzed, with concentrations between 38.7and 71.25 μg/kg. [4]

Fumonisins are mycotoxins produced by different fungi of the genus Fusarium. Within fumonisins, fumonisin FB1 is the most important in poultry production. Although birds are more resistant to this mycotoxin than other species, continuous exposure causes alterations at the intestinal and hepatic level.

Fumonisins block the synthesis of complex sphingolipids, which play an important role in protecting nerves, muscles, and membranes. This blockage causes the accumulation of free sphingoid bases, sphinganin (Sa) and sphingosine (So), which are highly toxic to most cells.

The liver is responsible for metabolizing these mycotoxins and is therefore where the toxic effect of these molecules occurs.

Poultry trials have shown that the administration of feed contaminated with fumonisins causes focal liver necrosis and gallbladder epithelium hyperplasia, as well as an increase in liver size. The increase in the size of an organ is related to worse physiological functioning of the organ (compensatory hyperplasia). [5]

Aflatoxins are mycotoxins produced by various fungi of the genus Aspergillus, with aflatoxin AFB1 being the most popular, given its toxigenic potential and prevalence. Aflatoxins have a marked hepatotoxic and hepatocarcinogenic effect. These mycotoxins work by altering lipid metabolism, causing fatty infiltration of the liver and vacuolar degeneration, which eventually a

ffects protein metabolism and organ functionality.[ 6]

Use of sorghum in feed formulation

Sorghum (Sorghum bicolor) is the second most produced cereal in Africa, with an annual production of more than 20 million tons, and the fifth worldwide. The advantage of this cereal is that its water requirements are lower than in the case of maize, making it possible to grow in arid areas.

Although the nutritional contribution of sorghum is like that of maize, it contains various anti-nutritional factors, such as the presence of condensed tannins, which reduce their digestibility and cause toxicity at the intestinal and hepatic level.

At the same time, sorghum contains a high phytate content, and the addition of specific enzymes (phytases) is necessary to ensure the digestibility of the grain. [7]

How to prevent these liver challenges?

 Adding pronutrients to the diet

Pronutrients are active molecules found in different botanical extracts that naturally optimize the physiological functioning of organs.

They act at the metagenetic level, increasing the expression of genes that were silenced or sub-expressed, thus increasing the synthesis of functional proteins in the target cells on which they act. [8]

10 classes of pronutrients have been identified depending on the target cell on which they act, among which it is worth highlighting: intestinal conditioner pronutrients   and liver conditioner pronutrients.

Intestinal conditioner pronutrients have as their target cell the enterocytes of the intestinal epithelium. These active molecules improve the mucosal state of the intestinal epithelium, ensuring the digestion and absorption of all components present in the diet and, therefore the growth of animals.

Intestinal conditioner pronutrients increase the renewal rate of enterocytes and improve tight junctions between intestinal cells, improving mucosal waterproofness and preventing pathogen settlement.

Given their effect on the gut health of birds, intestinal conditioner pronutrients are an effective alternative to the use of AGPs.

Intestinal conditioner pronutrients are absorbed and metabolized at the intestinal level, unlike AGPs, whose metabolization is mostly done at the liver level, causing liver over-strengthening that end up affecting the functionality of that organ. Additionally, intestinal conditioner pronutrients help mitigate the digestive-inflatory effect of tannins present in sorghum.

On the other hand, the liver conditioner pronutrients have as a target cell hepatocytes. These active molecules improve the renewal of hepatocytes and their functionality, increasing protein and lipid synthesis, improving fat digestibility and metabolism, and promoting the elimination of toxics and free radicals.

The addition of these liver conditioner pronutrients allows to ensure liver functionality after been exposed to different challenges, as well as recover its functionality after liver damage.

Studies carried out under field conditions have shown that the use of liver conditioner pronutrients has a marked positive effect on the production parameters and, therefore, on farm profitability.

In a study carried out with 94,000 broilers of the Ross 308 breed, it was observed that the administration of liver conditioner pronutrients, for 35 consecutive days, improves the final weight of animals by 1.19%, reduce the feed conversion rate by 2.89% and at the same time reduce mortality by 17.93%.

Mycotoxin binder – Silicoglycidol

The most effective way to avoid the hepatotoxic effect of mycotoxins is to prevent their absorption at the intestinal level. Therefore, adding in the diet a mycotoxin binder with a high binding percentage for these hepatotoxic mycotoxins is essential.

It is important that the binder has a low effective dose, so that it does not occupy a large part of the feed formula, leaving space for the rest of the nutrients. At the same time, it must have a high specificity, i.e., it captures only mycotoxins and not other nutrients present in the diet.

Silicoglycidol is a patented molecule, capable of biding in a high percentage all mycotoxins of interest in poultry production. It is an aluminum-silicate modified by a heat treatment and an ion exchange that modifies its molecular structure, increasing its biding surface, its spectrum of action and decreasing the uptake of other components of the diet such as amino acids or vitamins.

This molecule developed by Biovet S.A., act by creating hydrogen bridges with mycotoxins. These bonds are very stable and prevent the desorption of mycotoxins throughout the digestive tract, ensuring their elimination in feces.

Its addiction in feed, at a dose of 0.5 kg/t allows to capture effectively and selectively, mycotoxins at the intestinal level, avoiding their toxic effects on birds and ensuring their productivity.

Conclusion

The use of antibiotics for growth promoting purposes is at the same time an important risk factor for liver functionality since it is responsible for the metabolization of such drugs.

At the same time, poor feed quality, together with favorable weather conditions for the development of fungi and therefore for the accumulation of mycotoxins, make these a constant risk in African poultry. Many of these mycotoxins have a marked hepatotoxic effect, affecting the functionality of that organ.

Pronutrients, both intestinal conditioners and liver conditioners, improve gut and liver well-being. The first ones allow to replace AGPs, avoiding liver over-stress, and liver conditioner pronutrients allow to improve the functionality the liver, making it more resistant to toxics and speed up its recovery. The inclusion of these pronutrients in the diet allows to increase the meat produced by up to 22 tons per million broiler and, at the same time, reduce feed consumption by 80 tons.

Silicoglycidol, a patented mycotoxin binder, which allows to capture by more than 80% fumonisins and by more than 97.3% aflatoxins, present in feed, avoiding its hepatotoxic effects. It is a molecule with a high specificity that only captures mycotoxins and not other nutrients present in the feed.

Intestinal conditioner and liver conditioner pronutrients are marketed under the name Alquernat Nebsui and Alquernat Livol, respectively, from Biovet S.A.

Silicoglycidol is marketed in the line of micotoxin catchers Alquerfeed from Biovet S.A., which includes products such as Alquerfeed Antitox (100% Silicoglycidol-based).

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