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Journal ArticleDOI

A net carbohydrate and protein system for evaluating cattle diets: II. Carbohydrate and protein availability.

TL;DR: The Cornell Net Carbohydrate and Protein System has a submodel that predicts rates of feedstuff degradation in the rumen, the passage of undegraded feed to the lower gut, and the amount of ME and protein that is available to the animal.
Abstract: The Cornell Net Carbohydrate and Protein System (CNCPS) has a submodel that predicts rates of feedstuff degradation in the rumen, the passage of undegraded feed to the lower gut, and the amount of ME and protein that is available to the animal. In the CNCPS, structural carbohydrate (SC) and nonstructural carbohydrate (NSC) are estimated from sequential NDF analyses of the feed. Data from the literature are used to predict fractional rates of SC and NSC degradation. Crude protein is partitioned into five fractions. Fraction A is NPN, which is trichloroacetic (TCA) acid-soluble N. Unavailable or protein bound to cell wall (Fraction C) is derived from acid detergent insoluble nitrogen (ADIP), and slowly degraded true protein (Fraction B3) is neutral detergent insoluble nitrogen (NDIP) minus Fraction C. Rapidly degraded true protein (Fraction B1) is TCA-precipitable protein from the buffer-soluble protein minus NPN. True protein with an intermediate degradation rate (Fraction B2) is the remaining N. Protein degradation rates are estimated by an in vitro procedure that uses Streptomyces griseus protease, and a curve-peeling technique is used to identify rates for each fraction. The amount of carbohydrate or N that is digested in the rumen is determined by the relative rates of degradation and passage. Ruminal passage rates are a function of DMI, particle size, bulk density, and the type of feed that is consumed (e.g., forage vs cereal grain).
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Journal ArticleDOI
TL;DR: The Cornell Net Carbohydrate Protein Model (Chalupa et al., 1991) has developed the need for uniform procedures to partition feed nitrogen into A, B, and C fractions (Pichard and Van Soest, 1977) as mentioned in this paper.

2,282 citations

Journal ArticleDOI
TL;DR: It was concluded that optimum bacterial growth in the rumen occurs when EMPS is 29 g of bacterial N/kg of fermented organic matter, and ENU is 69%, implying that bacteria would require about 1.31 x rumen-available N per unit ofacterial N.

1,144 citations

Journal ArticleDOI
TL;DR: Recent work indicated that bacteria can also use futile cycles of potassium, ammonia, and protons through the cell membrane to dissipate ATP either directly or indirectly, and the utility of energy spilling in bacteria has been a curiosity.

810 citations

Journal ArticleDOI
TL;DR: The Cornell Net Carbohydrate and Protein System is a mathematical model that estimates cattle requirements and nutrient supply based on animal, environmental, and feed compositional information in diverse production situations to predict extent of ruminal fermentation, microbial protein production, post-ruminal absorption, and total supply of metabolizable energy and protein to the animal.

639 citations


Cites background or methods from "A net carbohydrate and protein syst..."

  • ...The CNCPS was first published in 1992 and 1993 in a series of four papers (Fox et al., 1992; Russell et al., 1992; Sniffen et al., 1992; O’Connor et al., 1993), but the model has been continually refined and improved over the last 10 years (Ainslie et al., 1993; Tylutki et al., 1994; Fox et al.,…...

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  • ...Many of the values in the original feed library (Sniffen et al., 1992) have been updated for the current feed library (Fox et al., 2003), based on recent studies with a gas production system (Pell and Schofield, 1993; Schofield et al., 1994; Schofield and Pell, 1995a,b; Stefanon et al., 1996; Pell…...

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  • ...The CNCPS uses experimentally measured digestibility coefficients to predict intestinal digestibilities and fecal losses (Sniffen et al., 1992; Knowlton et al., 1998)....

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  • ...Intestinal CHO B1 digestibility depends on type of grain, degree and type of processing, and level of intake above maintenance (Sniffen et al., 1992; Knowlton et al., 1998)....

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  • ...Estimates ofKd values for common feeds were developed (Sniffen et al., 1992) and have been expanded to over 150 feedstuffs (Tedeschi et al., 2001; Tedeschi et al., 2002b; Fox et al., 2003)....

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Journal ArticleDOI
TL;DR: Current production studies yield no clear evidence as to the benefits of postruminal digestion of starch to enhance milk yield or to change its composition, however, studies suggest that starch digested postruminally is used more efficiently for milk synthesis than that digested in the rumen.

606 citations

References
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01 Feb 1980

47,967 citations

Journal ArticleDOI
TL;DR: In addition to NDF, new improved methods for total dietary fiber and nonstarch polysaccharides including pectin and beta-glucans now are available and are also of interest in rumen fermentation.

23,302 citations

Book
12 Aug 1994

9,191 citations

Journal ArticleDOI
TL;DR: The Cornell Net Carbohydrate and Protein System (CNCPS) has a kinetic submodel that predicts ruminal fermentation and the protein-sparing effect of ionophores is accommodated by decreasing the rate of peptide uptake by 34%.
Abstract: The Cornell Net Carbohydrate and Protein System (CNCPS) has a kinetic submodel that predicts ruminal fermentation. The ruminal microbial population is divided into bacteria that ferment structural carbohydrate (SC) and those that ferment nonstructural carbohydrate (NSC). Protozoa are accommodated by a decrease in the theoretical maximum growth yield (.50 vs .40 g of cells per gram of carbohydrate fermented), and the yields are adjusted for maintenance requirements (.05 vs .150 g of cell dry weight per gram of carbohydrate fermented per hour for SC and NSC bacteria, respectively). Bacterial yield is decreased when forage NDF is < 20% (2.5% for every 1% decrease in NDF). The SC bacteria utilize only ammonia as a N source, but the NSC bacteria can utilize either ammonia or peptides. The yield of NSC bacteria is enhanced by as much as 18.7% when proteins or peptides are available. The NSC bacteria produce less ammonia when the carbohydrate fermentation (growth) rate is rapid, but 34% of the ammonia production is insensitive to the rate of carbohydrate fermentation. Ammonia production rates are moderated by the rate of peptide and amino acid uptake (.07 g of peptide per gram of cells per hour), and peptides and amino acids can pass out of the rumen if the rate of proteolysis is faster than the rate of peptide utilization. The protein-sparing effect of ionophores is accommodated by decreasing the rate of peptide uptake by 34%. Validation with published data of microbial flow from the rumen gave a regression with a slope of .94 and an r2 of .88.

1,283 citations