The biological model used by the NDS platform is the CNCPS version 6.2/6.5. It has been developed and refined over the past 30 years by the CNCPS modeling group at Cornell University to account of the most part of variations in nutrient requirements of cattle and feed utilization by different types of animals with different environmental and management conditions and feeds.
The goal of the model is to more accurately formulate rations to improve animal performance and to reduce overfeeding, feed costs and nutrient excretion. This requires the use of models which integrate the knowledge of factors affecting animal requirements (breed type and mature size, environmental effects, production level) and factors influencing nutrients derived from available feedstuffs (feed content of carbohydrate and protein fractions and their digestion and passage rates, microbial growth, and nutrient metabolism). Metabolizable energy (ME) and Metabolizable protein (MP) requirements vary according to breed, physiological state, environment, animal characteristics, management, and dietary factors. ME and MP supplied by the diet are based on quality and quantity of feed intake, ruminal carbohydrate fermentation and protein degradation, rumen microbial growth, nutrient passage to and absorption in the intestines, and nutrient partition for physiological functions. Rate of gain and milk production are predicted based on ME and MP available for productive purposes after maintenance and gestation requirements have been satisfied.
By definition a model is an integrated set of equations and transfer coefficients that describe the various physiological functions. Included are predictions of tissue requirements (maintenance, growth, pregnancy, lactation and tissue reserves), and supply of nutrients to meet requirements (dry matter intake, feed carbohydrate and protein fraction pool sizes and their characteristic digestion and passage rates, microbial growth, intestinal digestion and metabolism of absorbed nutrients).The purpose of a model is to mathematically describe the response of each compartment or several connected compartments to a variable or combination of variables. Most biological responses are integrated and nonlinear and change over time. This involves a combination of mechanistic and empirical approaches, which are generally steady state and static, using statistical representations of data that represent the aggregated response of whole compartments.
Among the main reasons why the CNCPS is one of the main biological models used on-site by nutrition practitioners is because it is based on robust and well accepted scientific foundations and it is enough easy to understand and efficient to use from the field perspective.