The Cornell Net Carbohydrate and Protein System: Updates to the model and evaluation of version 6.5

Abstract

New laboratory and animal sampling methods and data have been generated over the last 10 yr that had the potential to improve the predictions for energy, protein, and AA supply and requirements in the Cornell Net Carbohydrate and Protein System (CNCPS). The objectives of this study were to describe updates to the CNCPS and evaluate model performance against both literature and on-farm data. The changes to the feed library were significant and are reported in a separate manuscript. Degradation rates of protein and carbohydrate fractions were adjusted according to new fractionation schemes, and corresponding changes to equations used to calculate rumen outflows and postrumen digestion were presented. In response to the feed-library changes and an increased supply of essential AA because of updated contents of AA, a combined efficiency of use was adopted in place of separate calculations for maintenance and lactation to better represent the biology of the cow. Four different data sets were developed to evaluate Lys and Met requirements, rumen N balance, and milk yield predictions. In total 99 peer-reviewed studies with 389 treatments and 15 regional farms with 50 different diets were included. The broken-line model with plateau was used to identify the concentration of Lys and Met that maximizes milk protein yield and content. Results suggested concentrations of 7.00 and 2.60% of metabolizable protein (MP) for Lys and Met, respectively, for maximal protein yield and 6.77 and 2.85% of MP for Lys and Met, respectively, for maximal protein content. Updated AA concentrations were numerically higher for Lys and 11 to 18% higher for Met compared with CNCPS v6.0, and this is attributed to the increased content of Met and Lys in feeds that were previously incorrectly analyzed and described. The prediction of postruminal flows of N and milk yield were evaluated using the correlation coefficient from the BLUP (R(2)BLUP) procedure or model predictions (R(2)MDP) and the concordance correlation coefficient. The accuracy and precision of rumen-degradable N and undegradable N and bacterial N flows were improved with reduced bias. The CNCPS v6.5 predicted accurate and precise milk yield according to the first-limiting nutrient (MP or metabolizable energy) with a R(2)BLUP=0.97, R(2)MDP=0.78, and concordance correlation coefficient=0.83. Furthermore, MP-allowable milk was predicted with greater precision than metabolizable energy-allowable milk (R(2)MDP=0.82 and 0.76, respectively, for MP and metabolizable energy). Results suggest a significant improvement of the model, especially under conditions of MP limitation.

Updating the Cornell Net Carbohydrate and Protein System feed library and analyzing model sensitivity to feed inputs

“…Likewise, Velle et al (1997) infused free AA into the rumen at various rates and showed that up to 20% could escape degradation and flow through to the small intestine, which is in agreement with data from Volden et al (1998). Van Amburgh et al (2010) suggested it might be more appropriate to redefine the protein A1 fraction from NPN as described by Krishnamoorthy et al (1982) to ammonia. This would shift small peptides and free AA currently associated with the A1 fraction into the A2 fraction, where they could contribute to MP supply, and also refines the prediction of rumen N balance as less N is degraded in the rumen.…”

“…The intended methods for analyzing each major chemical component for use in the CNCPS are reported, as well as a sensitivity analysis of model outputs to variation in feed library inputs. An evaluation of model outputs and sensitivity relative to animal data is provided in a companion paper (Van Amburgh et al, 2015).…”

Determination of Energy and Protein Requirements of Sheep in Indonesia using a Meta-analytical Approach

“…This energy system is actually not ideal and therefore, current system has to be moved towards metabolizable energy (ME) or even net energy (NE) system (NRC, 2007;Van Duinkerken et al, 2011;Van Amburgh et al, 2015). Further, TDN data from various diets were obtained by estimations from their chemical composition and seldomly derived experimentally; such predictions may not be accurate since no study so far, to our knowledge, has validated the relationship between estimated TDN and measured TDN in the country.…”

“…This system is less accurate and current system has to be shifted to metabolizable protein (MP) system or its equivalent (NRC, 2007;Van Duinkerken et al, 2011;Das et al, 2014;Owens et al, 2014;Van Amburgh et al, 2015). The old CP system has a main disadvantage, i.e.…”

Efecto de Caryodendron orinocense sobre la degradación de la materia seca

“…La dinámica y la sincronía de degradación de los nutrientes permiten una mayor eficiencia en la digestibilidad del alimento, resultando en una mayor disponibilidad de nutrientes para los microorganismos del rumen y el hospedero (Russell et al, 1992). Es por esto que, los modelos de simulación de las dinámicas ruminales consideran las diferentes tasas de degradación de los nutrientes, lo cual permite explicar de una manera más aproximada los procesos de fermentación ruminal (NRC, 2001; Van-Amburgh et al, 2015). En este sentido, la alimentación de rumiantes debe estar enfocada en la degradación sincrónica de los nutrientes, lo que permite una mayor síntesis de proteína microbial y un mayor rendimiento productivo del animal (Miller et al, 2001).…”