scholarly journals Comparison and evaluation of mechanistic rumen models

1997 ◽  
Vol 78 (4) ◽  
pp. 563-581 ◽  
Author(s):  
A. Bannink ◽  
H. De Visser ◽  
A. M. Van Vuuren
Keyword(s):  
Fatty Acids ◽  
Organic Matter ◽  
Dairy Cows ◽  
Volatile Fatty Acids ◽  
Microbial Metabolism ◽  
Nutrient Flows ◽  
Lactating Dairy Cows ◽  
Wide Range ◽  
Physical And Chemical ◽  
Microbial N

Mechanistic rumen models of Baldwin (1995), Danfæer (1990) and Dijkstra et al. (1992) were compared on identical inputs that were derived from trials with lactating dairy cows fed on grass herbage. Consistent differences were detected between models and between predicted and observed outputs. None of the models seemed to predict all nutrient flows best. The models particularly differed in the representation of microbial metabolism: degradation of insoluble substrate, fermentation of substrate into volatile fatty acids, and incorporation of substrate into microbial matter. Differences amongst models in the prediction of these processes compensated for each other and consequently all models predicted the duodenal flow of non-NH3 N, microbial N and organic matter reasonably well. Large differences remained in the prediction of individual nutrient flows, however, and it was stressed that in order to enhance prediction of the profile of nutrient flows, the mechanisms of microbial metabolism need to be tested on their ability to describe the intraruminal transactions. However, this requires more-detailed information on individual nutrient flows and on the microbial or non-microbial origin of duodenal contents. Parameter inputs for physical and chemical feed properties were identified that are improperly defined in extant models or susceptible to error. The description of these feed characteristics needs to be developed further and become identifiable for a wide range of dietary conditions.

scholarly journals Absorption of volatile fatty acids from the rumen of lactating dairy cows as influenced by volatile fatty acid concentration, pH and rumen liquid volume

1993 ◽  
Vol 69 (2) ◽  
pp. 385-396 ◽  
Author(s):  
Jan Dijkstra ◽  
Huug Boer ◽  
Jaap Van Bruchem ◽  
Marianne Bruining ◽  
Seerp Tamminga
Keyword(s):  
Fatty Acids ◽  
Dairy Cows ◽  
Acid Concentration ◽  
Butyric Acid ◽  
Absorption Rate ◽  
Volatile Fatty Acids ◽  
Liquid Volume ◽  
Lactating Dairy Cows ◽  
Volatile Fatty Acid Concentration ◽  
Fractional Absorption

The effect of rumen liquid volume, pH and concentration of volatile fatty acids (VFA) on the rates of absorption of acetic, propionic and butyric acids from the rumen was examined in lactating dairy cows. Experimental solutions introduced into the emptied, washed rumen comprised two different volumes (10 or 30 1), four levels of pH (4.5, 5.4, 6.3, 7.2) and three levels of individual VFA concentrations (20, 50 or 100 mM-acetic, propionic or butyric acid). All solutions contained a total of 170 mM-VFA and an osmotic value of 400 mOsmol/l. Absorption rates were calculated from the disappearance of VFA from the rumen corrected for passage with liquid phase to the omasum. An increase in initial fluid pH caused a reduction in fractional absorption rates of propionic and butyric acids. Increasing the initial pH from 4.5 to 7.2 reduced fractional absorption rates of acetic, propionic and butyric acids from 0.35, 0.67 and 0.85 to 0.21, 0.35 and 0.28/h respectively. The fractional absorption rates of all VFA were reduced (P < 0.05) by an increase in initial rumen volume. The fractional absorption rate of acetic acid was lower (P < 0.05) at an initial concentration of 20 mM than of 50 mM. The fractional absorption rate of propionic acid tended (P < 0.10) to decrease as the level of concentration increased while fractional absorption rate of butyric acid was not affected by butyric acid concentration. These results indicate that relative concentrations of VFA in rumen fluid might not represent relative production rates and that attempts to estimate individual VFA production from substrate digestion must take account of pH and VFA concentration.

scholarly journals Volatile Fatty Acids in Ruminal Fluid Can Be Used to Predict Methane Yield of Dairy Cows

Animals ◽  
2019 ◽  
Vol 9 (12) ◽  
pp. 1006 ◽  
Author(s):  
S. Richard O. Williams ◽  
Murray. C. Hannah ◽  
Joe L. Jacobs ◽  
William J. Wales ◽  
Peter J. Moate
Keyword(s):  
Fatty Acids ◽  
Dairy Cows ◽  
Dry Matter ◽  
Sulfur Hexafluoride ◽  
Volatile Fatty Acids ◽  
Methane Yield ◽  
Dry Matter Intake ◽  
Published Data ◽  
Ruminal Fluid ◽  
Wide Range

The dry matter intake (DMI) of forage-fed cattle can be used to predict their methane emissions. However, many cattle are fed concentrate-rich diets that decrease their methane yield. A range of equations predicting methane yield exist, but most use information that is generally unavailable when animals are fed in groups or grazing. The aim of this research was to develop equations based on proportions of ruminal volatile-fatty-acids to predict methane yield of dairy cows fed forage-dominant as well as concentrate-rich diets. Data were collated from seven experiments with a total of 24 treatments, from 215 cows. Forage in the diets ranged from 440 to 1000 g/kg. Methane was measured either by open-circuit respiration chambers or a sulfur hexafluoride (SF6) technique. In all experiments, ruminal fluid was collected via the mouth approximately four hours after the start of feeding. Seven prediction equations were tested. Methane yield (MY) was equally best predicted by the following equations: MY = 4.08 × (acetate/propionate) + 7.05; MY = 3.28 × (acetate + butyrate)/propionate + 7.6; MY = 316/propionate + 4.4. These equations were validated against independent published data from both dairy and beef cattle consuming a wide range of diets. A concordance of 0.62 suggests these equations may be applicable for predicting methane yield from all cattle and not just dairy cows, with root mean-square error of prediction of 3.0 g CH4/kg dry matter intake.

The digestion of pasture plants by sheep. I. Ruminal production of volatile fatty acids by sheep offered diets of ryegrass and forage oats

1968 ◽  
Vol 19 (3) ◽  
pp. 419 ◽  
Author(s):  
RH Weston ◽  
JP Hogan
Keyword(s):  
Fatty Acids ◽  
Organic Matter ◽  
Crude Protein ◽  
Volatile Fatty Acids ◽  
Alimentary Tract ◽  
Soluble Carbohydrate ◽  
Wide Range ◽  
The Mean ◽  
Ad Libitum Intake ◽  
Pasture Plants

The production of volatile fatty acids (VFA) in the rumen of sheep was estimated by isotope dilution techniques. The 12 diets used consisted of dried ryegrass and forage oats and covered a wide range of levels of cell wall constituents (46–40% of the organic matter), crude protein (6–32%), and soluble carbohydrate (5–18%). Each diet was offered at a level equal to approximately 90% of the sheep's ad libitum intake. The production of VFA was correlated with the total amount of organic matter digested in the alimentary tract (r = 0.93–0.95). The mean VFA production per 100 g of organic matter digested in the alimentary tract was equivalent to 56.8 g, 243 kcal, or 0.85 mole. Values for individual diets varied about these means with a coefficient of variation of 6–7%. Rates of VFA production in, and VFA absorption from the rumen were correlated with VFA concentration in rumen liquor (r = 0.67, r = 0.67) and the rumen VFA pool (r = 0.81, r = 0.79). Approximately 76% of the VFA produced in the rumen was absorbed from the rumen, 19% was absorbed from the omasum and abomasum, and 5% passed from the abomasum to the intestines.

Improving the prediction of rumen volatile fatty acids in lactating dairy cows

1996 ◽  
Vol 1996 ◽  
pp. 240-240
Author(s):  
A. Bannink ◽  
J. France ◽  
J. Dijkstra
Keyword(s):  
Fatty Acids ◽  
Gastrointestinal Tract ◽  
Dairy Cows ◽  
Simulation Study ◽  
Volatile Fatty Acids ◽  
Metabolizable Energy ◽  
Accurate Prediction ◽  
Intermediary Metabolism ◽  
Molar Proportion ◽  
Lactating Dairy Cows

Volatile fatty acids (VFA) constitute the largest fraction of metabolizable energy absorbed from the gastrointestinal tract of dairy cows. The molar proportion of individual VFA is important because individual VFA have a different fate in intermediary metabolism. However, rumen models predict the VFA molar proportions inaccurately from feed characteristics (Dijkstra, 1993). To investigate what model elements are responsible for this inaccuracy, modified descriptions of several elements were tested and sensitivity of VFA predictions was determined. This simulation study aims to identify model elements whose improved description can contribute to a more accurate prediction of VFA molar proportions.

Improving the prediction of rumen volatile fatty acids in lactating dairy cows

1996 ◽  
Vol 1996 ◽  
pp. 240-240
Author(s):  
A. Bannink ◽  
J. France ◽  
J. Dijkstra
Keyword(s):  
Fatty Acids ◽  
Gastrointestinal Tract ◽  
Dairy Cows ◽  
Simulation Study ◽  
Volatile Fatty Acids ◽  
Metabolizable Energy ◽  
Accurate Prediction ◽  
Intermediary Metabolism ◽  
Molar Proportion ◽  
Lactating Dairy Cows

Volatile fatty acids (VFA) constitute the largest fraction of metabolizable energy absorbed from the gastrointestinal tract of dairy cows. The molar proportion of individual VFA is important because individual VFA have a different fate in intermediary metabolism. However, rumen models predict the VFA molar proportions inaccurately from feed characteristics (Dijkstra, 1993). To investigate what model elements are responsible for this inaccuracy, modified descriptions of several elements were tested and sensitivity of VFA predictions was determined. This simulation study aims to identify model elements whose improved description can contribute to a more accurate prediction of VFA molar proportions.

Utilisation of white clover silage fed alone or with maize silage by lactating dairy cows

1999 ◽  
Vol 39 (3) ◽  
pp. 237 ◽  
Author(s):  
D. E. Auldist ◽  
K. L. Atkinson ◽  
D. W. Dellow ◽  
M. J. Silvapulle ◽  
G. H. McDowell
Keyword(s):  
Fatty Acids ◽  
Dairy Cows ◽  
White Clover ◽  
Volatile Fatty Acids ◽  
Plasma Concentrations ◽  
Mixed Diet ◽  
Maize Silage ◽  
Dietary Nitrogen ◽  
Lactating Dairy Cows ◽  
High Yields

Six lactating dairy cows in mid lactation were fed either white clover silage or a mixture of white clover and maize silages (70 : 30, dry matter basis). Milk yields (about 20 L/day) and compositions were similar when cows were fed either diet. Although the mixed diet was less digestible and provided less energy and crude protein than white clover, rumen fermentation may have been improved relative to that when white clover silage was fed alone. Flow rates of fluid from the rumen were faster, pH values for rumen liquor were higher and concentrations of ammonia in rumen liquor were lower when cows were fed the mixed diet than white clover silage. Concentrations of total volatile fatty acids and the proportions of the major volatile fatty acids in rumen liquor were similar for both diets. The efficiency of utilisation of dietary nitrogen for liveweight gain and milk production also appeared to be similar for both diets. Plasma concentrations of key metabolites were consistent with the cows being well nourished when fed both diets. Overall, it was evident that white clover silage may be used effectively in combination with lower quality maize silage to meet the nutrient requirements of cows with reasonably high yields of milk during mid lactation.

scholarly journals Impact of Organic Loading Rate in Volatile Fatty Acids Production and Population Dynamics Using Microalgae Biomass as Substrate

2019 ◽  
Vol 9 (1) ◽  
Author(s):  
Jose Antonio Magdalena ◽  
Silvia Greses ◽  
Cristina González-Fernández
Keyword(s):  
Fatty Acids ◽  
Population Dynamics ◽  
Organic Matter ◽  
Anaerobic Digestion ◽  
Volatile Fatty Acids ◽  
Building Blocks ◽  
Biofuel Production ◽  
Organic Loading Rate ◽  
Organic Loading ◽  
Wide Range

AbstractVolatile fatty acids (VFAs) are regarded as building blocks with a wide range of applications, including biofuel production. The traditional anaerobic digestion used for biogas production can be alternatively employed for VFAs production. The present study aimed at maximizing VFAs productions from Chlorella vulgaris through anaerobic digestion by assessing the effect of stepwise organic loading rates (OLR) increases (3, 6, 9, 12 and 15 g COD L−1 d−1). The biological system was proven to be robust as organic matter conversion efficiency into VFAs increased from 0.30 ± 0.02 COD-VFAs/CODin at 3 g COD L−1 d−1 to 0.37 ± 0.02 COD-VFAs/CODin at 12 g COD L−1d−1. Even though, the hydrolytic step was similar for all studied scenario sCOD/tCOD = 0.52–0.58), the highest OLR (15 g COD L−1 d−1) did not show any further increase in VFAs conversion (0.29 ± 0.01 COD-VFAs/CODin). This fact suggested acidogenesis inhibition at 15 g COD L−1d−1. Butyric (23–32%), acetic (19–26%) and propionic acids (11–17%) were the most abundant bioproducts. Population dynamics analysis revealed microbial specialization, with a high presence of Firmicutes followed by Bacteroidetes. In addition, this investigation showed the microbial adaptation of Euryarchaeota species at the highest OLR (15 g COD L−1d−1), evidencing one of the main challenges in VFAs production (out-competition of archaea community to avoid product consumption). Stepwise OLR increase can be regarded as a tool to promote VFAs productions. However, acidogenic inhibition was reported at the highest OLR instead of the traditional hydrolytic barriers. The operational conditions imposed together with the high VFAs and ammonium concentrations might have affected the system yields. The relative abundance of Firmicutes (74%) and Bacteroidetes (20%), as main phyla, together with the reduction of Euryarchaeota phylum (0.5%) were found the best combination to promote organic matter conversion into VFAs.

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