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.

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.

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.

Factors affecting water intakes of lactating dairy cows offered grass silages differing in fermentation and intake characteristics

1998 ◽  
Vol 66 (3) ◽  
pp. 543-550 ◽  
Author(s):  
R. J. Dewhurst ◽  
N. W. Offer ◽  
C. Thomas
Keyword(s):  
Dairy Cows ◽  
Milk Yield ◽  
Water Intake ◽  
High Performance ◽  
Volatile Fatty Acids ◽  
Free Water ◽  
Metabolizable Energy ◽  
Factors Affecting ◽  
Lactating Dairy Cows ◽  
D Value

AbstractThe objective of this study was to investigate the effects of silage characteristics on water intake of lactating dairy cows and to examine the prediction of water intake. Sixteen grass silages, differing in fermentation and intake characteristics, were offered ad libitum to dairy cows in early lactation supplemented with 7 kg/day of concentrate (13·3 MJ metabolizable energy per kg dry matter (DM) and 216 g crude protein per kg DM). Four silages were offered in each of four incomplete change-over design experiments, consisting of three 3-week periods. Water intakes were recorded through individual Kent water meters and press water bowls over the final week of each period. Tree (drinking) water intake ranged from 20·1 to 89·9 (mean = 45·2; s.d. = 12·96) I/day whilst total water intake (also including food water) ranged from 48·4 to 123·8 (mean = 87·3; s.d. = 14·12) I/day. Water intake increased with increasing silage DM concentration, however free water replaced silage water at a rate less than 1. Milk yield and silage D value (digestible organic matter, g/kg DM) were strongly positively correlated with free water intake (r = 0·751 and 0·595 respectively), though fermentation indices were not good single predictors of water intake. Further analysis revealed problems owing to collinearity within the predictors of water intake: DM intake, silage D value and milk yields being significantly correlated, as were pH and volatile fatty acids as a proportion of total fermentation acids. The ridge regression technique was used to reduce collinearity problems and produce stable equations. The best prediction equations for water intake involved a combination of both animal and analytical information: diet DM concentration, milk yield and silage pH. The use of fermentation information, whether from titration or high-performance liquid chromatography did not describe real variation in water intake beyond that described by silage pH. Free water intake was higher with higher diet DM concentrations, higher milk yields and higher silage pH.

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.

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