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Investigating ruminal nitrogen metabolism

in vitro and in vivo studies using ¹⁵N-labelled forage nitrogen fractions

Vaga, Merko (2017). Investigating ruminal nitrogen metabolism. Diss. (sammanfattning/summary) Umeå : Sveriges lantbruksuniv., Acta Universitatis agriculturae Sueciae, 1652-6880 ; 2017:34
ISBN 978-91-576-8841-5
eISBN 978-91-576-8842-2
[Doctoral thesis]

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Abstract

Nitrogen losses from dairy production have negative impacts on the environment and on production economics. In Northern Europe, dairy cattle are mainly fed forage-based diets supplemented with protein feeds such as rapeseed meal. This thesis sought to develop and evaluate new methods for forage protein evaluation and to improve the value of locally produced protein feeds.

Ruminal metabolism of the grass silage soluble nitrogen (SN) fraction and of 15N-labelled ammonia was modelled based on degradation kinetics determined in vivo. Kinetic models were developed to provide an optimal fit between predicted and observed values of 15N atom excess in different rumen N pools. Microbial N synthesis was around 20% greater with soluble non-ammonia N (SNAN) than with ammonia N, proving that SNAN stimulates microbial growth. The protozoal contribution to direct protein degradation in cows fed at high intake was rather small, with around 95% of protozoal N originating from bacterial N. An estimated 12.5% of SNAN escaped ruminal degradation.

The in vitro degradation rates of SN fractions were very similar to those observed in other in vitro studies, but much lower than those measured in vivo. Immediate predicted microbial uptake of SN in grass silage was similar to that observed in vivo (20% and 14%, respectively), but significantly greater for red clover SN fractions (> 50%). Proportionally more grass silage insoluble N was degraded (detected) to ammonia N than of red clover, and of dried forages than of silage. Dried forage had a higher concentration of utilisable crude protein (uCP) than silage.

Heat treatment of legume seeds (field bean, lupin and peas) increased uCP concentrations, but high temperatures (over 140°C in oven or 120°C in autoclave for more than 30 min) also significantly increased the indigestible N fraction in the feeds.

The in vitro method shows potential for estimating uCP concentrations, but requires further development to estimate degradation of proteins in vivo. Using 15N-labelled forages is a promising method for future protein metabolism studies.

Authors/Creators:Vaga, Merko
Title:Investigating ruminal nitrogen metabolism
Subtitle:in vitro and in vivo studies using ¹⁵N-labelled forage nitrogen fractions
Series/Journal:Acta Universitatis agriculturae Sueciae (1652-6880)
Year of publishing :31 March 2017
Depositing date:3 March 2017
Volume:2017:34
Number of Pages:83
Papers/manuscripts:
NumberReferences
IM. Vaga, M. Hetta and P. Huhtanen (2016). Effects of heat treatment on protein feeds evaluated in vitro by the method of estimating utilisable crude protein at the duodenum. Journal of Animal Physiology and Animal Nutrition, doi:10.1111/jpn.12646.
IIS. Ahvenjärvi, M. Vaga, A. Vanhatalo, and P. Huhtanen (2017). Ruminal metabolism of grass silage soluble N fractions. Journal of Dairy Science (submitted).
IIIM. Vaga and P. Huhtanen. In vitro investigation of the ruminal digestion kinetics of different nitrogen fractions of ¹⁵N-labelled timothy. (manuscript).
IVM. Vaga and P. Huhtanen. In vitro investigation of the ruminal digestion kinetics of different nitrogen fractions of ¹⁵N-labelled red clover. (manuscript).
Place of Publication:Umeå
Publisher:Department of Agricultural Research for Northern Sweden, Swedish University of Agricultural Sciences
ISBN for printed version:978-91-576-8841-5
ISBN for electronic version:978-91-576-8842-2
ISSN:1652-6880
Language:English
Publication Type:Doctoral thesis
Full Text Status:Public
Agris subject categories.:L Animal production > L02 Animal feeding
L Animal production > L51 Animal physiology - Nutrition
Q Food science > Q54 Feed composition
Subjects:(A) Swedish standard research categories 2011 > 4 Agricultural Sciences > 402 Animal and Dairy Science > Animal and Dairy Science.
Agrovoc terms:ruminants, feeds, in vitro, in vivo experimentation, protein metabolism, nitrogen metabolism, digestible nitrogen, dairy cows, environmental impact
Keywords:dairy cow, utilisable crude protein, forages
URN:NBN:urn:nbn:se:slu:epsilon-e-3999
Permanent URL:
http://urn.kb.se/resolve?urn=urn:nbn:se:slu:epsilon-e-3999
ID Code:14125
Faculty:VH - Faculty of Veterinary Medicine and Animal Science
Department:(NL, NJ) > Dept. of Agricultural Research for Northern Sweden
(VH) > Dept. of Agricultural Research for Northern Sweden
External funders:FORMAS and Swedish Board of Agriculture
Deposited By: Mr Merko Vaga
Deposited On:06 Mar 2017 14:03
Metadata Last Modified:09 Mar 2017 09:18

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