A Rapid Procedure for Purine Measurement and Its Use for Estimating Net Ruminal Protein Synthesis

Many feeding trials have been conducted to quantify enteric methane (CH 4 ) production in ruminants. Although a relationship between diet composition, rumen fermentation and CH 4 production is generally accepted, the efforts to quantify this relationship within the same experiment remain scarce. In the present study, a data set was compiled from the results of three intensive respiration chamber trials with lactating rumen and intestinal fistulated Holstein cows, including measurements of rumen and intestinal digestion, rumen fermentation parameters and CH 4 production. Two approaches were used to calculate CH 4 from observations: (1) a rumen organic matter (OM) balance was derived from OM intake and duodenal organic matter flow (DOM) distinguishing various nutrients and (2) a rumen carbon balance was derived from carbon intake and duodenal carbon flow (DCARB). Duodenal flow was corrected for endogenous matter, and contribution of fermentation in the large intestine was accounted for. Hydrogen (H 2 ) arising from fermentation was calculated using the fermentation pattern measured in rumen fluid. CH 4 was calculated from H 2 production corrected for H 2 use with biohydrogenation of fatty acids. The DOM model overestimated CH 4 /kg dry matter intake (DMI) by 6.1% ( R 2 = 0.36) and the DCARB model underestimated CH 4 /kg DMI by 0.4% ( R 2 = 0.43). A stepwise regression of the difference between measured and calculated daily CH 4 production was conducted to examine explanations for the deviance. Dietary carbohydrate composition and rumen carbohydrate digestion were the main sources of inaccuracies for both models. Furthermore, differences were related to rumen ammonia concentration with the DOM model and to rumen pH and dietary fat with the DCARB model. Adding these parameters to the models and performing a multiple regression against observed daily CH 4 production resulted in R 2 of 0.66 and 0.72 for DOM and DCARB models, respectively. The diurnal pattern of CH 4 production followed that of rumen volatile fatty acid (VFA) concentration and the CH 4 to CO 2 production ratio, but was inverse to rumen pH and the rumen hydrogen balance calculated from 4 × (acetate + butyrate)/2 × (propionate + valerate). In conclusion, the amount of feed fermented was the most important factor determining variations in CH 4 production between animals, diets and during the day. Interactions between feed components, VFA absorption rates and variation between animals seemed to be factors that were complicating the accurate prediction of CH 4 . Using a ruminal carbon balance appeared to predict CH 4 production just as well as calculations based on rumen digestion of individual nutrients.Keywords: modelling methane, VFA, enteric fermentation, carbon, dairy cow Implications Methane (CH 4 ) is a potent greenhouse gas that arises from feed fermentation in the rumen and large intestine of ruminant animals. The quantity of CH 4 depends on daily feed intake, feed chemical composition and feed rumen digestibility. Therefore, the present paper was ...

“…Purines in rumen microbes and duodenal samples were analysed by spectrophotometry according to Zinn and Owens (1986) with modifications according to Thode (1999).…”

Section: Datamentioning

confidence: 99%

Methane production and diurnal variation measured in dairy cows and predicted from fermentation pattern and nutrient or carbon flow

Brask

Weisbjerg

Hellwing

et al. 2015

“…Microbial biomass was estimated using purine bases (adenine 1 guanine) as markers (Zinn and Owens, 1986). Data from VFA production and application of the stoichiometric theoretical equations (Demeyer, 1991;Van Soest, 1994;Groot et al, 1998) allowed the estimation of ATP production.…”

Section: Gas Production Incubationsmentioning

confidence: 99%

The influence of casein and urea as nitrogen sources on in vitro equine caecal fermentation

Santos

Ferreira

Martin‐Rosset

et al. 2012

To access the fermentative response of equine caecal microbial population to nitrogen availability, an in vitro study was conducted using caecal contents provided with adequate energy sources and nitrogen as limiting nutrient. Two nitrogen (N) sources were provided, protein (casein) and non-protein (urea). Caecal fluid, taken from three cannulated horses receiving a hay-concentrate diet, was mixed with a N-free buffer-mineral solution. The influence of four N levels (3.7, 6.3, 12.5 or 25 mg of N in casein or urea) was studied using the gas production technique. Total volatile fatty acids (VFA), NH 3 -N and gas production were measured after a 24-h incubation period. Microbial biomass was estimated using adenine and guanine bases as internal markers, and ATP production was estimated stoichiometrically. Microbial growth efficiency (Y ATP ) and gas efficiency (E gas ) were estimated. Fermentation with casein as the sole N source was generally characterized by lower total VFA, NH 3 -N, total gas production and higher acetate : propionate (A : P) ratio and Y ATP than with urea. Results herein presented indicate that, under these in vitro conditions, caecal microbial population does in fact use urea N, but less efficiently than casein in terms of microbial growth.

“…Duodenal flow of microbial FA was calculated from microbial FA content and duodenal flow of microbial organic matter (OM) (flow of duodenal microbial N divided by the ruminal bacterial N : OM ratio). Duodenal microbial N was derived from the ratio of purine to N in isolated bacteria and in duodenal samples (Zinn and Owens, 1986).…”

Section: Data Selection and Calculationmentioning

confidence: 99%

Digestion of fatty acids in ruminants: a meta-analysis of flows and variation factors. 1. Total fatty acids

Schmidely

Glasser

Doreau

et al. 2008

A database built from 95 experiments with 303 treatments was used to quantify the ruminal biohydrogenation (BH) of fatty acids (FA), efficiency of microbial protein synthesis (EMPS), duodenal flow and intestinal absorption of total FA and of FA with 12 to 18 C units, in response to variations in dietary FA content, source or technological treatment of fat supplement. Flows of FA were expressed relative to dry matter intake (DMI) to compile data from bovine and ovine species. BH tended to increase curvilinearly with FA intake, whereas dietary FA did not affect EMPS. A linear relationship between FA intake and duodenal flow of total FA was obtained, with a coefficient of 0.75 6 0.06 g duodenal FA/kg DMI for each g FA intake/kg DMI. Between experiments, positive balances of total FA (intake -duodenum) were related to low EMPS. Relationships between duodenal flows of FA with 12 to 18 C units and their respective intakes were linear, with a coefficient that increased with the number of C units. Duodenal flow of bacterial FA was linearly related to FA intake (coefficient 0.33 6 0.13), whereas contribution of bacterial lipid to duodenal flow decreased as FA intake increased. For each FA with 12 to 16 C units, prediction of FA absorption from its respective duodenal flow was linear. For total FA and FA with 18 C units, apparent absorption levelled off at high duodenal flows. All these relationships were discussed according to current knowledge on microbial metabolism in the rumen and on the intestinal digestibility of FA in the intestine.