In Belgium, the VEM/DVE system is traditionally used for ration evaluation. This system is user-friendly but remains static and takes little account of rumen fermentation dynamics. The CNCPS model (Cornell Net Carbohydrate and Protein System) offers a more physiologically based and time-dependent approach to energy and protein flows. Interest in this model is also growing among Belgian dairy farms. 

CNCPS is a dynamic feed evaluation model that simulates fermentation, passage, and digestion based on carbohydrate and protein fractions, each with its own degradation rate. The model predicts the availability of energy and nitrogen over time and calculates the supply of metabolizable protein, broken down by amino acids. 

Key components of CNCPS: 

• Passage and degradation rates (kp and kd) for each fraction 
• Dynamic prediction of microbial growth based on fermentable carbohydrates and rumen-available nitrogen 
• Models for rumen pH, fermentation rates, and peNDF (physical effective NDF) 
• Adjustments for animal-related factors (body weight, feed intake, lactation stage, body condition, heat stress, activity) 
• Prediction of metabolizable amino acids 

The result is a ration approach that closely matches the physiological reality of the dairy cow.

CNCPS distinguishes functional fractions for both carbohydrates and proteins, each with its own degradation and passage characteristics. For carbohydrates: 

• Fraction A: VFAs, organic acids, and sugars 
• Fraction B1: starch 
• Fraction B2: soluble fibers 
• Fraction B3: potentially digestible NDF 
• Fraction C: indigestible NDF 

 
For proteins, CNCPS also uses soluble, partially degradable, and indigestible fractions, allowing a more realistic estimation of protein supply over time. Each fraction has a kd value (degradation rate) and kp value (passage), enabling CNCPS to predict when nutrients become available to microbes and the animal. The kd value depends on feed characteristics, while the kp value depends on animal-related factors (lactation stage, intake, weight). CNCPS is therefore functionally dynamic, unlike the VEM/DVE system, which uses static passage rates. 

The digestibility of the B3 fraction (potentially digestible NDF) largely determines the energy supply from forages. CNCPS uses multi-point measurements of NDF digestibility, usually at four time points, to build an accurate fermentation curve. This contrasts with older static estimates, such as the traditional lignin × 2.4 formula, which assumes a fixed relationship between lignin content and indigestibility without considering fermentation rates. 
 
Advantages of the multi-point approach: 

• Better distinction between rapidly and slowly fermentable NDF 
• More realistic prediction of energy supply over time 
• More accurate estimation of rumen fill and DMI 
• Better basis for optimizing forages, whose digestibility can vary greatly 

 
Accurate estimation of NDF digestibility is essential not only for energy supply but also for the proper use of rumen-protected amino acids. Without reliable prediction of NDF digestibility, estimates of microbial protein production and amino acid requirements are less accurate. 

CNCPS calculates the supply of metabolizable protein broken down by individual amino acids. This allows much more precise control of amino acid supply than systems that only consider total metabolizable protein. Cow performance improves when the supply of essential amino acids matches her actual needs. Methionine and lysine are usually the first limiting amino acids in dairy rations and strongly influence milk protein and fat production. In some situations (rations very high in forage or low microbial protein production), histidine can also become limiting. 
 
This amino acid-focused approach gives the cow exactly the building blocks needed for efficient protein synthesis, resulting in higher milk production, better milk components, and a more stable metabolic profile. At the same time, the total crude protein level in the ration can decrease without performance loss, thanks to improved utilization. This reduces nitrogen excretion and improves the ratio between technical results and environmental efficiency. 

VDS Premix supports farms at every step in using CNCPS.

This support includes: 

• Analysis: assessment of fractions (A, B1, B2, B3, C), kd values, NDFd results, and amino acid profiles of forages and raw materials 
• Implementation of CNCPS software: assistance with starting ration calculation software (AMTS or NDS) 
• Standardization: working according to current CNCPS standards, adapted to your conditions, forage quality, and objectives 
• Ration calculation and optimization: formulation, simulation, and fine-tuning of CNCPS-based rations 
• Structural follow-up: periodic analysis of results and continuous optimization based on analyses and objectives 

 With this support, VDS ensures efficient and correct application of CNCPS, creating a uniform and reliable basis for ration calculation and optimization. 

Do you have any questions or would you like to know more? Please feel free to contact us! Our experts will be happy to help you.