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This month, I decided to speak about feed acid binding capacity. We are formulating our feed to match animal nutritional requirement. But to maximise nutrient bioavailability, we need to take into account as well the digestive functions . Ingested feed starts interacting with the acids produced in the stomach and it is critical to ensure that feed do not disrupt much digestive process.

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The stomach is the place where proteins are flocculated by pepsin enzyme. The optimal activity of pepsin in the stomach occurs at a pH between 2 and 3.5. The pepsin transforms tri-dimensional protein structure into bi-dimensional one in order for the protease to later access amino-acids bonds to be broken. The stomach cells are naturally producing acids to maintain low pH, pH 2 for an adult and pH 4 for a newborn piglet. At weaning, a combination of low acid secretion and consumption of large meals can result in elevated pH, often to over 5.0 and it may remain high for several days (Kidder and Manners, 1978). The high acid-binding capacity of the feed (its ability to neutralise acid) helps further to raise the stomach pH (Prohaszha and Baron, 1980; Jasaitis et al., 1987; Bolduan and al.,1988).

chart pepsin optimum activity
To minimize the increase of pH during the meal ingestion, nutritionist must select for their formulation raw materials that do not bind acids much. This is critically important on young animal whose pH is already high (pH 4 for young piglets).

To classify each ingredient Acid Binding Capacity (ABC), we prepare an aqueous solution with 1 kg of each ingredient and we measure the quantity of acid to be added to reach a pH of 4. The quantity of acids required (ABC4 in mEq/kg) will qualify each ingredient. The more the ingredient will bind acids and the more acids will be required to lower the pH, the higher will be the ABC4 index (in mEq/kg). The table below present the ABC4 value obtains by Lund Jensen method.
Minerals have extremely high ABC 4 values. They have indeed the ability to bind acids and high incorporation of minerals in the feed would require higher production of endogenous acids from the piglet stomach to return its pH to normal. Among all minerals, Zinc Oxide has the highest ABC 4. Its addition in the feed at high dosage will impact the piglet stomach pH and disturb the protein flocculation and digestion physiological process. At the opposite, the organic acids have negative value as they support decrease of pH in the stomach. But all organic are not equals. Based on ABC4, Formic acid is the most powerful ingredient. These ABC 4 index enable us to calculate the ABC 4 value of each feed by calculating weighted average of each ingredient index. By experimentation, it has been demonstrated that the range of ABC 4 for an optimal feed performance is between 280 and 320 mEq/kg of feed. The experience shows as well that the results can be very different for every feed found on the market depending on each company formulation strategy. Feed with high ABC4 will compromise animal growth whereas a low ABC4 would impair piglet feed intake. The graph below shows that the prevalence of diarrheas increase when feed ABC value gets higher.

To optimize feed ABC 4, the company Animine developed an online tool that you can consult by clicking this link ABC SIMULATOR . It will enable you to simulate the ABC4 value of feed formulas. You will find in this table the ABC4 index of most popular ingredients and by entering each ingredient inclusion, you can calculate the ABC4 value of your existing feed formulas. You have the possibility as well to do some simulations and optimize your feed ABC4 value by adjusting inclusions. You can visualize your results in the graph on the right side of the screen.

ABC calculator your current situation

You can as well create one ABC4 ‘nutrient’ in your formulation software and enter each ingredient ABC4 value into the matrix. Thus, you will monitor the binding capacity of each formulation. If your current feed ABC4 value is far from the optimum, I advice you to adjust your formulation and you may find useful the following advices;

1 – Reduce Zinc Oxide dosage

With a very high binding capacity (+16321 mEq/Kg), the incorporation of high dosage of Zinc Oxide would hurt your feed ABC4. Based on ABC4 value, we estimate that 3Kg of standard Zinc Oxide would actualise neutralise about 5 Kg of Fumaric acid. At the current price of Fumaric acids, the amount of acids wasted could actualize jeopardize the economical balance of the feed. The new high porosity technology as HiZox enable to reduce the incorporation of Zinc Oxide from 3000ppm to only 200-300ppm which would reduce interaction with organic acids and improve your feed ABC4 value. I encourage you to make your own simulation on Animine ABC4 simulation tool.

2 – Change organic acids source
Based on the ABC4 value, Formic acids will have the most beneficial effect in supporting stomach pH reduction. It may be necessary as well to adjust the optimal dosage in order to ensure that your feed ABC4 gets between the targeted windows of 280-320 mEq/Kg.

3 – Reduce Carbonate Calcium
Carbonate Calcium is often considered as a good source of Calcium but actually his effect on feed ABC4 value is detrimental. We should therefore limit its use as much as we can and replace it when it possible by other source of Calcium as Calcium formiate (that would offer better ABC4 value - 12,932 mEq for CaCO3 against 3,983 mEq for Ca formiate)

4 – Replace Dicalcium Phosphate by Monocalcium Phosphate
A simple way to reduce ABC4 value in a feed is to shift the source of Phosphate based on their ABC4 value (3,098 mEq for DiCalcium Phosphate against 291 mEq for MonoCalcium Phosphate).

I encourage you to visualise the impact of these changes on your feed ABC4 value by doing some simulation on Animine ABC tool.

Click Here to Visit ABC calculator

All these adjustment should be made within the existing constraints of nutritional value and costs. By modifying the source of trace minerals, we will affect as well the dietary electrolytes balance (DET). But this is another topic that we will cover in our next newsletter.

If you need help in calculating your feed ABC value, I would be happy to help you. Please contact me at

Related tags: ABC Value - Acidifier - Zinc - dEB
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