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Substrate levels, carbohydrate degradation rate and their effects on ruminal end-product formation

Sveinbjörnsson, Jóhannes (2006). Substrate levels, carbohydrate degradation rate and their effects on ruminal end-product formation. Diss. (sammanfattning/summary) Uppsala : Sveriges lantbruksuniv., Acta Universitatis agriculturae Sueciae, 1652-6880 ; 2006:26
ISBN 91-576-7075-7
[Doctoral thesis]

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Abstract

New feed evaluation systems for ruminants, based on dynamic-mechanistic models and predictions of production responses to nutrients, demand accurate prediction of end-products formed during rumen fermentation. The aim of the present work was to investigate the effects of levels of different substrates and carbohydrate degradation rates upon ruminal end-product formation. An in vitro method was introduced to evaluate feeds with respect to ruminal starch degradation. The method was based on incubation of feed samples in a buffered rumen fluid solution and a subsequent enzymatic analysis of remaining starch. Heat treatment generally increased rate or extent of starch degradation to glucose. Use of single time point determinations correlated reasonably well with degradation rate estimates and offers the possibility to reduce the cost of analysis. Two experiments with a 2x2x2 factorial arrangement of treatments were performed with an in vitro rumen simulation technique (SIMCO) to investigate the direct effects and interactions of several dietary factors upon ruminal fermentation. Response in volatile fatty acid (VFA) proportions to starch level was dependent on starch and neutral detergent fibre (NDF) sources. Faster degradation rates of starch and NDF had a positive effect upon microbial N efficiency and the propionate proportion. Increasing the level of N improved microbial N efficiency and increased the proportion of propionate and butyrate at the expense of acetate. Increased feeding level resulted in a lower microbial N efficiency and a lower proportion of propionate. The results of the two in vitro experiments clearly point out that rumen VFA proportions and microbial N efficiency are not only affected by the level of different substrates fermented in the rumen but also their degradation rates. Data from Nordic dairy cow experiments were analysed and modeled with respect to effects of feed characteristics upon rumen fermentation patterns. The final model differed relative to published VFA models by predicting a smaller effects of starch but large effects of silage lactate levels on propionate proportions. To improve the prediction of end-product formation, better characterization of feeds are needed. Carbohydrate degradation rate and type of forage are factors that probably should be included in future models.

Authors/Creators:Sveinbjörnsson, Jóhannes
Title:Substrate levels, carbohydrate degradation rate and their effects on ruminal end-product formation
Year of publishing :March 2006
Volume:2006:26
Number of Pages:54
Papers/manuscripts:
NumberReferences
ALLI. Sveinbjörnsson, J., Murphy, M. Udén, P. 2006. In vitro evaluation of starch degradation from feeds with or without heat-treatments. Submitted. II. Sveinbjörnsson, J., Murphy, M., Udén, P. 2006. Effect of the proportions of neutral detergent fibre and starch, and their degradation rates, on in vitro ruminal fermentation. Animal Feed Science and Technology. In Press. III. Sveinbjörnsson, J., Murphy, M., Udén, P. 2006. Effect of the level of dry matter and protein and degradation rate of starch on in vitro ruminal fermentation. Animal Feed Science and Technology. In Press. IV. Sveinbjörnsson, J., Huhtanen, P. Udén, P. 2006. The Nordic dairy cow model Karoline – development of VFA sub-model. In: Nutrient digestion and utilisation in farm animals: modelling approaches. Edited by E. Kebreab, J. Dijkstra, A. Bannink, W. J. J. Gerrits & J. France. CAB International, Wallingford, UK, pp. 1-14. In Press.
Place of Publication:Uppsala
ISBN for printed version:91-576-7075-7
ISSN:1652-6880
Language:English
Publication Type:Doctoral thesis
Full Text Status:Public
Agrovoc terms:dairy cattle, ruminants, fermentation, rumen digestion, starch, degradation, carbohydrates, in vitro experimentation
Keywords:dairy cattle, in vitro technique, modelling, microbial N efficiency, rumen fermentation, starch degradation stochiometry, VFA
URN:NBN:urn:nbn:se:slu:epsilon-1000
Permanent URL:
http://urn.kb.se/resolve?urn=urn:nbn:se:slu:epsilon-1000
ID Code:1076
Department:(VH) > Dept. of Animal Nutrition and Management
Deposited By: Jóhannes Sveinbjörnsson
Deposited On:31 Mar 2006 00:00
Metadata Last Modified:02 Dec 2014 10:09

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