SID (strong ion difference) assay

The Strong Ion Difference (SID) is a biochemical parameter used to assess acid-base balance in biological and nutritional matrices. It is based on the difference between strong cations and strong anions present in a sample, including Na⁺, K⁺, Cl⁻, Ca²⁺, and Mg²⁺. This concept, derived from Stewart's acid-base model, is more representative than classical approaches based solely on pH or bicarbonate.

The SID makes it possible to identify or anticipate metabolic imbalances such as acidosis, alkalosis or electrolyte disturbances that can impact animal performance, general health and body fluid homeostasis.

Analytical methods used

SID measurement requires precise ionic measurements obtained by electrochemistry or atomic spectrometry. YesWeLab partner laboratories use the following methods depending on the matrix:

• Electrochemistry for major electrolytes
• ICP-OES or ICP-MS for measuring low-concentration minerals, complex solutions, or digested solid matrices

For individual elements, these analyses can be supplemented by dedicated services already available in the YesWeLab catalog, such as calcium or magnesium assays . When a matrix requires more extensive characterization, multi-element analysis by ICP-MS can be integrated into the protocol.

Applications in animal nutrition and veterinary health

SID is one of the key parameters for calculating DCAD (Dietary Cation-Anion Difference), particularly in ruminants for the prevention of peripartum hypocalcemia or metabolic disorders related to calving. It is also used in formulations for poultry, swine, equines, and companion animals.

It helps to optimize:
• Electrolyte balance management
• Maintenance of performance under heat stress
• Feed and water consumption
• Immunity and resistance to infections
• Growth and ADG (average daily gain)

SID is also used in the study of drinking water, complementing mineral profiling and conductivity. Water analysis can therefore be integrated when SID is studied within a broader zootechnical context.

Types of matrices analyzed

The SID assay proposed by YesWeLab is applicable to numerous matrices:

• Animal serums or biological fluids
• Mineral and vitamin premixes
• Complete or complementary feeds
• Nutritional additives
• Electrolyte solutions
• Drinking water
• Liquid or solid veterinary products

For a more complete view of nutritional quality, SID can be combined with protein analysis amino acid assay or vitamin analysis as needed.

Interest in formulation and quality control

An unbalanced SID can cause:
• Decreased feed intake
• Decreased productivity
• Increased oxidative stress
• A higher risk of acidosis or alkalosis
• A decline in livestock performance

Conversely, a formulation optimized according to the SID improves performance, hydration, stress resistance, and ionic homeostasis.

YesWeLab supports formulators, nutritionists and veterinary structures in the implementation of SID-based strategies, particularly for feed intended for young animals, sporting animals or animals subjected to demanding environmental conditions.

YesWeLab Services

YesWeLab performs SID testing using a network of partner laboratories specializing in ionic analysis, accredited to ISO 17025 or operating according to validated methodologies. Methods are selected based on the matrix, the desired level of precision, and nutritional objectives.

Our digital platform facilitates complete service management: ordering, analysis tracking, sample traceability, and results retrieval. SID analyses can be combined with other services from the catalog for a more comprehensive assessment of electrolyte or nutritional status.

For any specific needs or quote requests, please contact our scientific team.