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Dietary electrolyte balance (dEB)
Dr Ioannis Mavromichalis
When we formulate diets for pigs, little attention is paid usually on
minerals, apart from meeting certain specifications and only for just a few of
them. Yet, minerals are extremely important especially because the balance among
them affects metabolism in a very profound way. Let's see how this little known
nutritional topic can influence animal performance.
When we formulate diets for pigs, little attention is paid usually on
minerals, apart from meeting certain specifications and only for just a few of
them. Yet, minerals are extremely important especially because the balance among
them affects metabolism in a very profound way. Let's see how this little known
nutritional topic can influence animal performance.
The balance of
dietary cations (positively charged ions) and anions (negatively charged ions)
is in close relationship with pig performance and affects metabolism quite
differently than individual 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). A more comprehensive estimate,
however, takes into account also the contribution of divalent ions (that is,
calcium, magnesium, sulfur, and phosphorus), but it is used less often because
it requires more chemical analyses.
Equation
The equation below
is the most widely used form of dEB taking into account easily obtained analyses
for sodium (Na), potassium (K), and chlorine (Cl).
dEB (mEq/kg) = 1,000 ×
[Na(g/kg)/23 + K(g/kg)/39 - Cl(g/kg)/35.5]
The dietary electrolyte
balance is an indication of the metabolisable ions that can generate or consume
acid during metabolism. Diets with negative dEB are more likely to cause
metabolic acidosis than diets with positive dEB. Metabolic acidosis has been
implicated with reduced feed intake. 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.
It is widely accepted that dEB below zero is
associated with depressed performance and health in pigs, whereas values between
0 and 300 mEq/ kg are considered more appropriate, albeit research results have
been variable.
Ingredient selection
Dietary ingredient
selection strongly interacts with dEB. For example, piglets fed a diet high in
non-starch polysaccharides (15%), an unusual diet for young pigs, benefit from
low dEB (-100 mEq/kg), whereas pigs fed a diet lower in non-starch
polysaccharides (10%) benefit from higher dEB (200 mEq/kg). Nutrient
digestibility, particularly dry matter, energy, protein, and chlorine, are also
affected in a similar fashion by dietary electrolyte balance.
Until more
research is conducted, dEB around 200-250 mEq/kg feed should be satisfactory for
most piglet and sow diets, whereas values around 150 mEq/kg for finishing pigs
are used frequently without problems.
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