Effect of maturity on digestion kinetics of water-soluble and water-insoluble fractions of alfalfa and brome hay (original) (raw)
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Journal of dairy science, 1995
Gas output from in vitro digestion of forage can be used to measure both forage digestibility and the kinetics of microbial digestion. Two different approaches are used to measure gas volumes: 1) either the gas is collected at atmospheric pressure and its volume determined directly, or 2) the gas accumulates in a fixed volume container, and the volume is calculated from pressure changes. We have used the latter technique to study the in vitro digestion of alfalfa, timothy, and corn silage by ruminal microorganisms in bottles of different sizes. We measured pH changes, NDF disappearance, and VFA concentrations and characterized the digestion profiles using a single- or dual-pool logistic model. Bottle size had a slight effect on pH but was not associated with changes in any of the other characteristics measured including the kinetic parameters. Gas measurements based on pressure increases in a fixed volume container appear to offer a valid alternative to methods based on gas collecti...
Evaluation of nutritional properties of alfalfa and sainfoin forages by gas production techniques
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Two forage species alfalfa (Medicago sativa), and sainfoin (Onobrychis viciifolia Scop.), at two consecutive growing season (spring and summer), were studied for their chemical composition and in vitro gas production characteristics. Data on cumulative gas production (mL gas/g DM) were fitted to the non-sigmoidal model, and for evaluation of model, the concordance correlation coefficient (CCC) was used to assess the agreement between predicted and observed data. Chemical analysis showed that nutrient composition was affected by the forage type. Concentration of fiber components (NDF, ADF, cellulose and crude fiber) were higher in alfalfa compared to sainfoin (P 0.05). The results showed that there is a great potential for improving the analytical capacity of the technique, by reducing the length of incubation from 48 to 24 h for studies on high quality forages. This study showed that 24 h incubation provided informative results with high reproducibility of the measurements, clear re...
Effects of concentrate on forage digestion in vitro , pH and volatile fatty acids
2007
It is common practice in the dairy industry to use a mixed concentrate and forage diet. The ways in which feeds interact in the rumen at early time points to affect digestion are not characterized. Further understanding of concentrate-forage relationships could aid in the development of a more efcient diet. The objective of this study was to determine the early effects (0-6h) of concentrate type on rumen pH and forage digestion in vitro. An initial trial was conducted to compare the effect of buffer strength (full vs. half) on pH change during in vitro digestion of orchard grass (Dactylis glomerata L.) with or without sucrose. It was determined that using a full strength buffer allowed for sufcient changes in pH for the purposes of this study with the observed pH for the full strength buffer dropping from 6.6 to 5.4. Two forages, orchardgrass and corn (Zea mays L.) stover were combined with 5 concentrate treatments (no concentrate, corn meal, corn gluten meal, barley (Hordeum vulg...
Journal of The Science of Food and Agriculture, 2005
The objective of this experiment was to evaluate the influence of preservation methods on the fermentation kinetics of carbohydrate fractions of fresh forage, hay and silage of oats, which have been harvested at the milky stage of grain ripening. Samples of unfractionated forage (WF), residue insoluble in 90% ethanol (EIR) and isolated neutral detergent fibre (NDF) were fermented in vitro and the gas production was monitored. To obtain the gas production and fermentation kinetics of the ethanol-soluble fraction (A fraction) the gas produced from the EIR fermentation was subtracted from the WF gas at each time point. The same approach was used to obtain the gas production and fermentation kinetics of the fraction insoluble in 90% ethanol but soluble in neutral detergent solution (B1 fraction), by subtracting the isolated NDF gas curve from the corresponding EIR curve. The fractional maximum rate of gas production (RM) was lower for both preserved forages (p < 0.01 for silage; p < 0.05 for hay) than for fresh forage. Ensiling did not change the size of the A fraction but reduced by 40% its RM (p < 0.01) compared with fresh forage. The potential gas production from the B1 fraction and its RM were reduced by 19% (p < 0.01) and 44% (p < 0.05), respectively. RM of both A and B1 fractions was the same for hay and fresh forage. The curve subtraction technique may be used to obtain an estimation of the rate for neutral detergent-soluble fractions and to determine changes due to ensiling and haymaking on the rate of gas produced. Copyright © 2005 Society of Chemical Industry