A dynamic simulation model of nutrient digestion
in the rumen of dairy cows

Petruzzi, H. J.; Danfær, A.; Nørgaard, P.

doi:10.22358/jafs/67829/2002

Cited by 5 publications

(9 citation statements)

References 48 publications

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“…This short-term adaptation delays the disposal of energy by microbes. Consequently, whereas fractional degradation rates of 150% to 300%/h are assumed for WSC in some rumen models Petruzzi et al, 2002), a much lower fractional degradation is more likely, but experimental evidence is lacking. Satisfactory adjustments are obtained assuming a fractional rate of around 40%/h (D. Sauvant, unpublished).…”

Section: Starchmentioning

confidence: 99%

“…Concerning passage rate, two or three outflow rates are generally considered. The liquid and the solid phases are either considered globally , or separated between forage and concentrate particles Lescoat and Sauvant, 1995), or between large and small particles (Baldwin et al, 1987b;Petruzzi et al, 2002). Although most models represent the effect of intake level on flow rates, equations vary widely among models.…”

Section: Carbohydrate Digestion and Nutrient Fluxesmentioning

confidence: 99%

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Carbohydrate quantitative digestion and absorption in ruminants: from feed starch and fibre to nutrients available for tissues

Nozière

Ortigues-Marty

Loncke

et al. 2010

Animal

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Carbohydrates are the main source of energy in ruminants. Their site, extent and kinetics of digestion highly impact the amount and profile of nutrients delivered to peripheral tissues, and the responses of the animal, i.e. ingestion, efficiency of production, N and methane excretion, quality of products and welfare. Development of multi-objective feed evaluation systems thus requires a more integrated quantitative knowledge on carbohydrate digestion and yield of terminal products, as well as on their metabolism by splanchnic tissues. The objective of this paper is to review (i) quantitative knowledge on fibre, starch and sugar digestion, volatile fatty acids (VFA) and glucose production and splanchnic metabolism and (ii) modelling approaches which aim at representing and/or predicting nutrient fluxes in the digestive tract, portal and hepatic drainage. It shows that the representation of carbohydrate digestion and VFA yield is relatively homogeneous among models. Although published quantitative comparisons of these models are scarce, they stress that prediction of fibre digestion and VFA yield and composition is still not good enough for use in feed formulation, whereas prediction of microbial N yield and ruminal starch digestion seems to be more satisfactory. Uncertainties on VFA stoichiometric coefficients and absorption rates may partly explain the poor predictions of VFA. Hardly any mechanistic models have been developed on portal-drained viscera (PDV) metabolism whereas a few exist for liver metabolism. A qualitative comparison of these models is presented. Most are focused on dairy cows and their level of aggregation in the representation of nutrient fluxes and metabolism highly differs depending on their objectives. Quantitative comparison of these models is still lacking. However, recent advances have been achieved with the empirical prediction of VFA and glucose production and fluxes through PDV and liver based on the current INRA feed evaluation system. These advances are presented. They illustrate that empirical prediction of ruminal VFA and intestinal glucose production can be evaluated by comparison with measured net portal net fluxes. We also illustrate the potential synergy between empirical and mechanistic modelling. It is concluded that concomitant empirical and mechanistic approach may likely help to progress towards development of multi-objective feed evaluation systems based on nutrient fluxes.

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Section: Starchmentioning

confidence: 99%

Section: Carbohydrate Digestion and Nutrient Fluxesmentioning

confidence: 99%

Carbohydrate quantitative digestion and absorption in ruminants: from feed starch and fibre to nutrients available for tissues

Nozière

Ortigues-Marty

Loncke

et al. 2010

Animal

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“…(K_EP;0.2856). From the analysis of the rumen model on which the feed intake regulation model is based (see Petruzzi et al, 2002), it was demonstrated that the rumen model was sensitive to parameters defining the rate constant of passage of small particles (KpSP) and the digestion rate constant of NDF. Hence, parameters a (0.01), b (0.052) and d (3.2) were also included in the sensitivity analysis of FIRM.…”

Section: Methodsmentioning

confidence: 99%

“…Decomposition of the mean square prediction error (MSPE) into error due to central tendency (ECT), error due to regression (ER) and error due to disturbance (ED) was done as defined by Bibby and Toutenberg (1977). Significance and formulas to calculate these terms were also presented in Petruzzi et al (2002). The RMSPE expressed as a percentage of the observed mean is used as a measure of the prediction error.…”

Section: Evaluation Techniquesmentioning

confidence: 99%

“…The range of values tested in the sensitivity analysis for K_EP is possibly out of range of the normal values found in the literature and extreme values should not be considered. Bequette (2002) estimated that a dairy cow loses 22 g of endogenous protein per kg of DM intake, whereas Ferrel (1995) The last group of parameters evaluated (a, b, d) were proved to have an impact on the output from the rumen model (Petruzzi et al, 2002). In general the sensibility of FIRM is low to these parameters.…”

Section: From Sensitivity Analysismentioning

confidence: 99%

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A dynamic model of feed intake regulation in dairy cows. Model evaluation

Petruzzi¹,

Danfær²,

Friggens³

2004

J. Anim. Feed Sci.

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The objective of this work was the evaluation of a feed intake regulation model for dairy cows described in a previous paper. Sensibility analysis revealed that the model is sensible mainly to those parameters defining the upper limit of NDF rumen digesta. The level of sensibility varies with the energy content of the diet evaluated and with the time in the lactation cycle where the sensibility analysis is done. A total of 17 treatments from a series of experiments were used to compare experimentally observed feed intake and body condition score (BCS) of dairy cows with model predictions of these variables. Feed intake, either throughout the whole lactation period or as an average for a certain period of it, is predicted by the model with an acceptable degree of accuracy for most of the treatments. Typical curves of feed intake are predicted by the model for most of the treatments. Accuracy of prediction of BCS depends on the treatment being evaluated. However, losses of BCS are predicted at the beginning of the lactation period followed by a gradual increase in BCS. The interplay between energy transactions and rumen digesta load constitutes an acceptable framework on which mechanistic models of feed intake regulation can be developed.

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In vitro evaluation of sugar digestibility in molasses

Palmonari

Cavallini

Sniffen³

et al. 2021

Italian Journal of Animal Science

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Beet and cane molasses mainly contain mono-di-, and tri-saccharides, composed by hexoses, as well as pentoses in traces. However, rationing software consider sugars as only one entity, with a rate of digestion $20% h À1 . The aim of this initial study was to investigate and evaluate the in vitro digestion dynamics and rates of the sugar fraction in molasses. Three beet and three cane molasses were randomly selected from a variety of samples collected world-wide and digested via in vitro rumen fermentation, at 1, 2, 3, 4, 6, 8, and 24 h. Samples were then analysed with a specific enzymatic kit to quantify residual sucrose, glucose, fructose, raffinose, galactose, and arabinose. Complete disappearance of sucrose happened within 3 hours of incubation. Glucose and fructose were completely digested within 4-6 h, showing variability among samples. Even if not so representative, galactose showed a similar trend of digestion (97% digestion within 3-4 h). Raffinose was quite slower in cane molasses, while it was completely digested within 1 h in beet molasses. Arabinose, a pentose, never reached a complete digestion, and its fermentation dynamic was different compared to other sugars. Calculated rates of digestion for sucrose, glucose and fructose, most representative sugars in molasses, were higher than 50% h À1 in both cane and beet. Obtained results showed that sugar fraction in molasses may vary, and different sugars are rapidly fermented by rumen microbes. Modern rationing models should consider a modification of sugar rates of digestion, since the actual one appears too slow than those observed in vitro. HIGHLIGHTS Molasses are unique blends of several sugars Major sugars are digested in few hours Rationing software should consider a faster rate of digestion for different sugars ARTICLE HISTORY

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A dynamic simulation model of nutrient digestion in the rumen of dairy cows

Cited by 5 publications

References 48 publications

Carbohydrate quantitative digestion and absorption in ruminants: from feed starch and fibre to nutrients available for tissues

Carbohydrate quantitative digestion and absorption in ruminants: from feed starch and fibre to nutrients available for tissues

A dynamic model of feed intake regulation in dairy cows. Model evaluation

In vitro evaluation of sugar digestibility in molasses

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