The additivity of predicted ATP yields from feedstuffs incubated in vitro with rumen fluid

Rumen micro-organisms ferment feeds to short chain fatty acids (SCFA) with the production of ATP. Measuring SCFA concentration in vitro could therefore be used to predict the yield of ATP in vitro. This estimate could then be used to predict the yield of synthesised microbial biomass. However, feeds may interact when they are incubated together, and so it is quite possible that ATP yield is not additive. The objectives of this experiment were therefore to determine whether the yield of total SCFA produced by feed mixtures was additive, and also whether the ATP yield of feed mixtures could be predicted from the calculated ATP yield of the individual feeds.

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Influence of diet on growth yields of rumen micro-organisms in vitro andin vivo: influence on growth yield of variable carbon fluxes to fermentation products

British Journal Of Nutrition ◽

10.1079/bjn2003934 ◽

2003 ◽

Vol 90 (3) ◽

pp. 625-634 ◽

Cited By ~ 41

Author(s):

M. Blümmel ◽

A. Karsli ◽

J. R. Russell

Keyword(s):

Fatty Acids ◽

Microbial Biomass ◽

Short Chain Fatty Acids ◽

Gas Production ◽

Microbial Production ◽

Short Chain ◽

Maize Grain ◽

Chain Fatty Acids

The efficiency of rumen microbial production (EMP)in vitroandin vivowas examined for three roughages (lucerne (Medicago sativaL.) hay, oat (Avenia sativaL.)–berseem clover (Trifolium alexandrinumcultivar BigBee) hay and maize (Zea maysL.) crop residue (MCR)) and for five isonitrogenous (106 g crude protein (N × 6·25)/kg) diets formulated from lucerne hay, oat–berseem clover hay, MCR, soya-bean meal and maize grain to provide degradable intake protein for the production of 130 g microbial protein/kg total digestible nutrients. EMPin vivowas determined by intestinal purine recovery in sheep and ranged from 240 to 360 g microbial biomass/kg organic matter truly degraded in MCR and in one of the diets respectively (P<0·05). EMPin vitrowas estimated by the substrate degraded: gas volume produced thereby (termed partitioning factor, PF (mg/ml)) at times of estimated peak microbial production and after 16·0 and 24·0h of incubation. For the diets, PF values were significantly related to EMPin vivoat peak microbial production (P= 0·04), but not after 16·0 (P= 0·08) and 24·0h (P= 0·66). For roughages, PF values were significantly related to EMPin vivoonly when measured after 16·0 h (P= 0·04). For MCR and diets, a close non-linear relationship was found between PF values at peak microbial production and EMPin vivo(R20·99,P<0·0001) suggesting a maximum EMPin vivoof 0·39. Low gas production per unit substrate degraded (high PF) was associated with high EMPin vivo.Thein vitrostudy of the products of fermentation, short-chain fatty acids, gases and microbial biomass (by purine analysis) after 16·0h of incubation showed very strong relationships (R2≥ 0·89,P<0·0001) between short-chain fatty acids, gases and gravimetrically measured apparent degradability. Except for maize grain, the true degradability of organic matter estimated by neutral-detergent solution treatment agreed with the sum of the products of fermentation (R20·81,P=0·0004). After 16·0h of incubation, the synergistic effects of diet ingredient on diets were greater for microbial biomass (18%) than for short-chain fatty acids and gas production (7 %). It is concluded that measurement of gas production only gives incomplete information about fodder quality; complementation of gas measurements by true degradability measurements is recommended.

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The amount of rumen fluid influences the composition of short chain fatty acids produced in vitro

BSAP Occasional Publication ◽

10.1017/s146398150004231x ◽

2006 ◽

Vol 34 ◽

pp. 87-92

Author(s):

S. Muetzel ◽

R.M. Mauricio ◽

K. Becker

Keyword(s):

Fatty Acids ◽

Rumen Fluid ◽

Short Chain Fatty Acids ◽

Gas Production ◽

Short Chain ◽

Microbial Composition ◽

Fatty Acid Production ◽

Fermentation Products ◽

Chain Fatty Acids

SummaryIn vitro rumen incubation systems are widely used to determine substrate degradation and the amount of fermentation products like gases, short chain fatty acids and the microbial biomass produced. Here we compare the influence of the amount of inoculum used for preparing the incubation medium on short chain fatty acid production and composition. Treatments were 10% and 30% (v/v) of filtered rumen fluid used for inoculation. In a series of experiments it was demonstrated that the two treatments did not alter the gas production or the amount of substrate truly degraded. However, SCFA production (especially acetate) was significantly reduced when only 10% of inoculum were used for incubation. We propose that acetate was taken up by rumen microorganisms as a precursor for growth, although it cannot be excluded that an altered microbial composition contributed to the observed differences.

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