From : Shutterschock

Last month, we presented an article about the stomach pH. This month, we will address the mechanisms involved to maintain the blood pH and how feed is influencing it. The mechanisms presented are very relevant in tropical climate as South East Asia and we are underestimating their importance when we are formulating feeds in our part of the world I hope that you will find the information below useful !!!

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Maintenance of blood acid-base equilibrium is fundamental to life. Enzyme systems, metabolic functions and performance measures depend on this equilibrium. The pH of blood is maintained in the range 7.3 – 7.5 by buffer systems based essentially on HCO3- (bicarbonate ion). In tropical conditions, Animals need to fight against high temperature. Panting respiration is an important reaction in the effort to cool the body by evaporative cooling through loss of water from lungs. Thirst is increased, more urine is excreted and with it key electrolytes. Animals are depleted in HCO3- from increased urine excretion and the loss of CO2 from hyperventilation. Blood pH balance is then endangered.

Animals will need to get HCO3- rebalanced in order to stabilize blood pH. HCO3- ion will be absorbed by the intestinal cells according to the cations-anions gradient. HCO3- anions are using the same pump as Sodium and Potassium to pass the cell transporter. To increase absorption of bicarbonate anion, we need to provide sufficient Sodium and Potassium cations and reduce Chloride anion to the ration. In case, we want to slow down absorption of bicarbonate anion, we should reduce supply of cations and increase anions. To optimize metabolism and maximize animals’ performance, it is critical to monitor the balance of dietary cations (positively charged ions) and anions (negatively charged ions). The dietary electrolyte balance (dEB), also known as cation-anion difference (CAD), is calculated using only monovalent ions (that is, sodium, potassium, and chlorine).

 - The equation below is the most widely used form of dEB taking into account the results of feed analysis regarding contents in (Na), potassium (K), and chlorine (Cl).

dEB (mEq/kg) = [Na(g/kg)/23 + K(g/kg)/39 - Cl(g/kg)/35.5]

Diets with low dEB are more likely to cause metabolic acidosis than diets with high dEB. Metabolic acidosis has been implicated with reduced feed intake and low growth performance. Dietary electrolyte balance may also affect energy, amino acid, vitamin, and mineral metabolism.

For example, excess dietary alkalinity (positive dEB) may increase lysine oxidation and, thus, increase the requirement for lysine.

For optimal animal performance, we should look at formulating feed to reach the following dEB.