Revising electrolyte balance in broiler in a sustainable feed manufacturing strategy

Among chloride-free sodium sources available to supplement in feed, AdiSodium is a cost-effective source, ensuring animal performance in standard and hot climate conditions. Exhibiting a low carbon footprint, this source has benefits on sustainability for animal production by improving litter quality & reducing ammonia volatilization…

Monogastric feeds need to be balanced in dietary electrolytes (sodium, potassium and chloride), as they are essential elements for various physiological functions. Those needs are challenged nowadays with new feeding practices (protein reduction, alternative raw material, etc). For sodium, the supply is generally complemented with a chloride-free source of sodium with the aim of ensuring animal performance. AdiSodium, Adisseo sodium sulphate at 32% Na concentration, is a suitable candidate for this purpose. This sodium source is of high quality, benefiting from rigorous and continuous industrial quality control, cost-effective and with a reduced carbon footprint.

ADISODIUM: A COST-EFFECTIVE AND SUSTAINABLE SODIUM SOURCE FOR MODERN FEEDS AND FARMS
There are different chloride-free sources of sodium available in the market under carbonate, bicarbonate, or sulfate forms. The sulfate form of sodium such as AdiSodium has demonstrated some advantages in regards with other sources. As reported in previous studies, AdiSodium leads to lower litter pH value, without affecting litter moisture, tending to reduce footpad lesion score. This effect on litter pH has been also reported as a possible mechanism in a lower litter ammonia volatilization in comparison with sodium bicarbonate (Mercier et al. 2005).

Adisseo is committed to reduce direct environmental footprint by achieving 2025 emissions reduction target for greenhouse gasses emissions (-20% on scope 1 and 2 vs 2020), energy (-12% vs 2020) and water usage (-20% vs 2020). Those commitments are shaped via innovation in current industrial processes or new product development and projects in Adisseo facilities, especially in industrial plants. This results in the reduction of products’ carbon footprints, as for instance for AdiSodium.

In the Roches-Roussillon plant (France), where AdiSodium is produced, we have partnered in the DECLYC project to expedite decarbonisation efforts in Lyon Vallée de la Chimie (Chemistry Valley). This has a targeted reduction of 80% of CO₂ emissions by 2050, equivalent to 1.6 million tonnes of CO₂ annually, aligning with national sustainability goals.

To assess environmental footprint, we have adopted the Life Cycle Assessments (LCA) methodology. As AdiSodium is a coproduct of methionine with a relatively low value versus the main product, the economic allocation of the global carbon footprint is extremely favorable to the coproduct. This explains why, among all chloride-free sodium sources, AdiSodium has an extremely low climate change value per sodium unit. This LCA report on AdiSodium has finally a value for feed millers who can include these data in their own feeds’ life cycle assessments. But the full benefit really lies in the integration of the positive impact of AdiSodium on the sustainability of animal production.

DIETARY ELECTROLYTES CONSIDERATIONS IN EVOLVING FEED FORMULATIONS TO ENSURE SUSTAINABLE ANIMAL PERFORMANCE
Dietary electrolytes supply and its relationship with plasmatic Acid-Base homeostasis have been studied in broilers in the early 80’s by Mongin. The relationship between the monovalent ions Na⁺, Cl^– and K⁺ with the blood pH was clearly established and explained through physiological processes. This effect is, on one hand, related to absorption and ions exchanges at intestinal level with K⁺ and Na⁺ playing alkalogenic effect by exchanging with H⁺, whereas Cl^– is acidogenic by exchanging with HCO_3^–. On a second hand, this effect is due to cations / anions balance, mainly summarized to Na⁺ and Cl^–at plasma level, that manage the required room for the carbonate buffering system.

According to these works, the weighed sum of these mains ions, called Dietary Electrolytic Balance (DEB) and expressed as mEq/kg of feed, was recommended in the range of 220-240 for broilers as an optimum value to ensure optimal growth rate and Feed Conversion Ratio (FCR).

However, since that time, feed formulation constraints (strategies), raw materials and synthetic amino availability have changed significantly leading to reduce and substitute soybean meal inclusion in broiler’s feed.

Potassium is the only electrolyte that is not specifically supplemented in the diet, meaning its level in feed depends on the used cereals and oilseed-meals and their inclusion rates. Among these raw materials, soybean meal is by far the richest in potassium and all strategies resulting in soybean meal inclusion rate reduction will result also in a DEB decrease.

On top of that, crude protein and/or soybean meal substitution mechanically increases the inclusion of lysine that, if supplemented under hydrochloride form, participates also to decrease the DEB value. Thus, maintaining the previously determined DEB target of 220 mEq/kg of feed is not affordable (reachable) anymore.

REVISITING DEB TARGET VALUE IN LOW PROTEIN DIET STRATEGY
Beyond economic and environmental questions, animal physiology and blood pH regulation continue to follow the same rules and the electrolytes balance needs to be maintained to ensure proper homeostasis. A recent study set-up at the Scottish Agricultural College proposes to address the question of determining the minimum dietary potassium level and re-address the optimum DEB value for broilers in a context of low Crude Protein diet (17.5%). The first outcomes are that the minimum potassium level is in between 0.63 – 0.7 % and increasing potassium level above this value has no effect on performance. The second outcome is to re-affirm the validity of maintaining a minimum Na/Cl ratio at 1.00, when potassium is low, to optimize FCR (Figure 1). But, increasing this ratio above 1, continues to improve Body Weight Gain (Figure 2). It was also observed that DEB value can be lower than previously established in this new formulation context.

DEB values above 190 mEq/kg of feed allow maintaining an optimal FCR during the period: 0-24 days of age with a low potassium level.

Increasing sodium level to reach DEB of 220-240 would lead to an increase in water intake and hence litter moisture that is not desired. The recommendation is to have a Na/Cl ratio as close as possible to 1 with a targeted dietary level in the range 0.20-0.23% for Na and Cl. The difficulty here is more to limit chloride than to increase sodium and some choice must be made to achieve the target. In fact, Acid-Base homeostasis of blood is under the domination of sodium and chloride ions whereas potassium is mainly intracellular. This means that chloride excess directly impacts the plasmatic buffering potential by anions excess, increasing the risk of metabolic acidosis due to reduced blood buffering capacity.

CONCLUSION
While electrolytes levels in feed in general should be more investigated with regards to new feeding practices, the need to supply sodium without chloride remains. Among chloride-free sodium sources available to supplement in feed, AdiSodium is a cost-effective source, ensuring animal performance in standard and hot climate conditions. Exhibiting a low carbon footprint, this source has benefits on sustainability for animal production by improving litter quality & reducing ammonia volatilization, thus improving animal & human well-being, and decreasing acidification.

About Dr. Yves Mercier
Dr. Yves Mercier graduated in 1999 with a PhD in nutrition and food science. With almost 30 years of experience in animal research, he has been in Adisseo’s R&I team for 20 years. Mercier has been Adisseo Rhodimet Scientific and Technical’s global manager since 2017 and is the leader of the amino acid metabolism team in R&I nutrition monogastric. Mercier was appointed as expert in Amino acids metabolism in 2021. His work focuses on amino acids nutrition and low protein diets to participate to the sustainable development of the worldwide animal production.