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United States Department of Agriculture

Agricultural Research Service

Research Project: IMPROVED PLANT GENETIC RESOURCES FOR PASTURES AND RANGELANDS IN THE TEMPERATE SEMIARID REGIONS OF THE WESTERN U.S.

Location: Forage and Range Research

Title: Differential Ruminal Degradation of Alfalfa Proteins

Authors
item Chen, Dong -
item Peel, Michael
item Olson, Kenneth -
item Weimer, Bart -
item Dewald, Daryll -

Submitted to: Canadian Journal of Plant Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: June 24, 2009
Publication Date: November 1, 2009
Citation: Chen, D., Peel, M., Olson, K.C., Weimer, B.C., Dewald, D.B. 2009. Differential Ruminal Degradation of Alfalfa Proteins. Canadian Journal of Plant Science. 89:1065-1074.

Interpretive Summary: Alfalfa is high in protein that is rapidly and extensively degraded in the rumen. Increasing protein escape from the rumen is a global issue and would provide an economic benefit to the livestock industry, particularly the dairy industry. Development of alfalfas with increased ruminal protein bypass will require the ability to identify proteins that are not degraded in the rumen and those alfalfa plants that contain those proteins. The objective of this research was to develop a protocol where individual proteins could be characterized for their ruminal degradation. Using gel electrophoresis, it was demonstrated that individual proteins from alfalfa could be separated for ther relative degradation in the rumen. Using the protocol, 26 individual proteins were characterized, representing about 40% of the total alfalfa protein. Most importantly, it was demonstrated differences for protein degradation could be detected. The research showed that although all proteins were degraded over time, the rate and amount of degradation was dramatically different among them. Individual proteins characterized ranged in mass from 41% to 0.29% of the total mass of protein characterized. The ability to separate proteins based ruminal degradation suggests there is potential to select for protein that degrades more slowly and possibly escapes the rumen.

Technical Abstract: Alfalfa (Medicago sativa L.) has high crude protein that is rapidly and extensively degraaded in the rumen. Our objective was to develop a protocol where individual proteins could be characterized for their ruminal degradation. Proteins from individual genotypes of three alfalfa cultivars were characterized using fluorescence 2D difference gel electrophoresis combined with MALDI-TOF mass spectrometry for protein identification. Twenty-six proteins were characterized, representing between 33 and 41% of the total protein among genotypes. Variation for protein degradation was observed among proteins after 45 and 120 min of incubation in the rumen of a Holstein steer (PBO.001). After 45 min of ruminal incubation, nine proteins averaged 75% or more remaining, 12 had 50% or less remaining, and five were intermediate. After 120 min of ruminal incubation, four proteins averaged greater than 80%, seven between 80 and 50%, and 15 less than 50% remaining. Although all proteins were degraded over time, the rate and amount of degradation was dramatically different among them. The rate of digestion differed (P_0.05) for 3 and 10 proteins among genotypes after 45 and 120 min, respectively. Individual proteins characterized ranged in mass from 41 to 0.29% of the total mass of protein characterized. Total content of those proteins that differed for rate of digestion ranged from 7 to 1%. The results demonstrate that individual proteins can be characterized for their ruminal degradataion. The ability to separate proteins based ruminal degradation suggests there is potential to select for protein that degrades more slowly and possibly escapes the rumen.

Last Modified: 8/22/2014
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