Multiphasic analysis of gas production kinetics for in vitro fermentation of ruminant feeds

Five morphological fractions (leaf blade, leaf sheath, stem, husk and cob) of stover of five maize genotypes, namely waxy, conventional, fodder, sweet and high-oil maize, respectively, were used to test the effects of genotype and morphological fractions on chemical composition and in vitro fermentation characteristics. The waxy maize had a higher (P , 0.05) stem but lower (P , 0.05) leaf blade proportion and fodder maize had a higher (P , 0.05) leaf blade but lower (P , 0.05) leaf sheath proportion than other genotypes, respectively. Maize genotype had a significant effect (P , 0.001) on the chemical composition of stover parts except for organic matter (OM) concentration. Chemical composition of stover parts was affected (P , 0.001) by morphological fractions. The interaction effects between genotype and morphological fraction on the fiber content of stover parts were significant. Over 0.40 and 0.50 of phosphorus (P) and crude protein (CP) of whole-plant maize stover were averagely contributed by leaf blade. Leaf blade, stem and cob contributed over 0.75 of OM, CP, P and fiber in the whole plant. There were significant effects of genotype and morphological fraction on both in vitro gas production parameters and in vitro organic matter disappearance of maize stovers. The genotype and morphological fraction of maize stover and their interaction had significant effects on NH 3 -N and total volatile fatty acid concentration and the molar proportion of volatile fatty acid in the supernatant after 72 h of incubation except for valeric acid. The present data indicated that the genotype and morphological fraction of maize resulted in variation in the nutritive value of maize stover.

Section: Resultsmentioning

confidence: 99%

Morphological fractions, chemical composition and in vitro fermentation characteristics of maize stover of five genotypes

Tang

Gan

Tan

et al. 2008

“…The MM and GM models both might not increase continuously with longer incubation time and have different characteristics from other models. For the MM model (Groot et al, 1996), the FRD increases initially to a maximum value and decreases or continuously decreases till the minimum FRD, depending on the shape parameter. For the GM model , the FRD can be constant, can decrease or increase asymptotically with time, depending on the rate constant.…”

Section: Discussionmentioning

confidence: 99%

“…Therefore, there are large differences in the FRD among the LE 0 , MM and GM models (Figure 3), resulting from different underlying assumptions included in the models. The LE 0 , MM and GM models are developed on the basis of the conception of microbial growth and substrate degradation (Wang et al, 2011), enzyme reactions (Groot et al, 1996) and substrate surface and complete invasion by microbes (France et al, 1993), respectively. It is widely accepted that FRG and the FRD are different concepts Ló pez et al, 2007).…”

Section: Discussionmentioning

confidence: 99%

“…Curve fitting The LE 0 (Wang et al, 2011), the EXP LAG (Schofield et al, 1994), the GM (France et al, 1993) and the MM (Groot et al, 1996) models were compared for their ability in revealing fermentation processes from the gas production curve (Table 2 and Figure 3). The NLREG version 5.4 software (Sherrod, 1995) was used to calculate fermentation parameters with the four models tested.…”

Section: Logistic-exponential (Le) Modelmentioning

confidence: 99%

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Deriving fractional rate of degradation of logistic-exponential (LE) model to evaluate early in vitro fermentation

Wang

Sun

Tang

et al. 2013

Water-soluble components of feedstuffs are mainly utilized during the early phase of microbial fermentation, which could be deemed an important determinant of gas production behavior in vitro. Many studies proposed that the fractional rate of degradation (FRD) estimated by fitting gas production curves to mathematical models might be used to characterize the early incubation for in vitro systems. In this study, the mathematical concept of FRD was developed on the basis of the Logistic-Exponential (LE) model, with initial gas volume being zero (LE 0 ). The FRD of the LE 0 model exhibits a continuous increase from initial (FRD 0 ) toward final asymptotic value (FRD F ) with longer incubation time. The relationships between the FRD and gas production at incubation times 2, 4, 6, 8, 12 and 24 h were compared for four models, in addition to LE 0 , Generalization of the Mitscherlich (GM), c th order Michaelis-Menten (MM) and Exponential with a discrete LAG (EXP LAG ). A total of 94 in vitro gas curves from four subsets with a wide range of feedstuffs from different laboratories and incubation periods were used for model testing. Results indicated that compared with the GM, MM and EXP LAG models, the FRD of LE 0 model consistently had stronger correlations with gas production across the four subsets, especially at incubation times 2, 4, 6, 8 and 12 h. Thus, the LE 0 model was deemed to provide a better representation of the early fermentation rates. Furthermore, the FRD 0 also exhibited strong correlations (P , 0.05) with gas production at early incubation times 2, 4, 6 and 8 h across all four subsets. In summary, the FRD of LE 0 model provides an alternative to quantify the rate of early stage incubation, and its initial value could be an important starting parameter of rate.Keywords: mathematical models, rate of gas production, logistic-exponential model, in vitro fermentation ImplicationsThe fractional rate of degradation (FRD) of LE 0 model generally had high correlation with gas production at 2, 4, 6 and 8 h across all four subsets tested, and thus provides a good alternative to reveal the rate of early stage in vitro fermentation. The FRD of LE 0 model would have an implication in quantifying the rate of fermentation and evaluating digestion efficiency of feedstuffs in the rumen, as ruminal retention time of feedstuffs is short. However, further studies are needed to testify whether a higher FRD leads to a higher nutritive value (e.g. volatile fatty acid profile, microbial protein synthesis and feedstuff digestibility) for ruminants.

“…Calculations and statistical analyses Total gas production was calculated as the amount of gas produced per gram organic matter (OM) of substrate initially incubated (termed OMCV = organic matter corrected volume; in ml/g OM) after fitting a monophasic model (Groot et al, 1996):…”

Section: Microbial Composition Profilingmentioning

confidence: 99%

Adaptation of faecal microbiota in sows after diet changes and consequences for in vitro fermentation capacity

Sappok

Gutiérrez

Smidt

et al. 2015

In vitro gas production studies are routinely used to assess the metabolic capacity of intestinal microbiota to ferment dietary fibre sources. The faecal inocula used during the in vitro gas production procedure are most often obtained from animals adapted to a certain diet. The present study was designed to assess whether 19 days of adaptation to a diet are sufficient for faecal inocula of pigs to reach a stable microbial composition and activity as determined by in vitro gas production. Eighteen multiparous sows were allotted to one of two treatments for three weeks: a diet high in fibre (H) or a diet low in fibre (L). After this 3-week period, the H group was transferred to the low fibre diet (HL-treatment) while the L group was transferred to the diet high in fibre (LH-treatment). Faecal samples were collected from each sow at 1, 4, 7, 10, 13, 16 and 19 days after the diet change and prepared as inoculum used for incubation with three contrasting fermentable substrates: oligofructose, soya pectin and cellulose. In addition, inocula were characterised using a phylogenetic microarray targeting the pig gastrointestinal tract microbiota. Time after diet change had an effect ( P < 0.05) on total gas production for the medium-fast fermentable substrates; soya pectin and oligofructose. For the more slowly fermentable cellulose, all measured fermentation parameters were consistently higher ( P < 0.05) for animals in the HL-treatment. Diet changes led to significant changes in relative abundance of specific bacteria, especially for members of the Bacteroidetes and Bacilli, which, respectively, increased or decreased for the LH-treatment, while changes were opposite for the HL-treatment. Changing the diet of sows led to changes in fermentation activity of the faecal microbiota and in composition of the microbiota over time. Adaptation of the microbiota as assessed by gas production occurred faster for LH-animals for fast fermentable substrates compared with HL-animals. Overall, adaptation of the large intestinal microbiota of sows as a result of ingestion of low and high fibre diets seems to take longer than 19 days, especially for the ability to ferment slowly fermentable substrates.