Nutrient Value of Selected Weeds in Oregon

February 24, 2006

By: Amy Peters, Livestock Agent

and Cassie Bouska, Ag. Research Assistant

Preliminary Report to Agricultural Research Foundation

Nutrient Value of Selected Weeds in Oregon

ARF 8084

The objective of this project was to determine the nutrient content of various common invasive weed species at various developmental stages during the year and compare that to nutrient requirements of livestock.  Do these weeds have sufficient quality to be considered satisfactory feed?  If yes, would livestock grazing within infested areas add to tools available for weed control?  To be an economically viable alternative, the nutrient value of the weeds needs to be determined. 

Currently, one year of data has been collected for weed species during three seasons: fall (August 2004), spring (April 2005), and summer (July 2005).  One more year of data collection is necessary to complete the project.  After weeds are analyzed this year, they will be compared to beef, sheep, and goat requirements at all stages of production.  Weeds most likely to be eaten by each species will be summarized together.

Table 1, using ewes at maintenance, typifies the analyses that will be conducted at the conclusion of this study.  An animal’s energy requirement for maintenance is that amount of dietary energy it must consume daily to neither gain nor lose body energy.  Preliminary data analysis of weeds compared to nutrient requirements of ewes at maintenance suggests that some of the weeds meet protein and energy requirements at some times during the year.  Many of the mineral profiles exceeded recommended levels and many may be toxic. 

Data so far indicates that the rushes and yellow toadflax do not meet nutrient requirements of ewes at maintenance.  Himalaya blackberry meets the crude protein requirement but does not meet a ewe’s spring energy requirement.  The calcium requirements are not met with Himalaya blackberry and the phosphorous requirements are only met in the fall.  Blackberry exceeds the recommendation for iron and manganese but other mineral requirements are not met.  Meadow knapweed meets a ewe’s requirement for protein but the other knapweeds only met requirements spring and summer.  Yellow starthistle was only adequate for protein in summer and energy requirements were only met in spring.  Canada thistle met protein requirements only in fall and bull thistle met requirements in spring.  Canada thistle met energy requirements but bull thistle only met requirements in spring and summer.  

Table 1.  Preliminary results of nutrient content of selected weeds compared to nutrient requirements of ewes at maintenance.  Marked boxes indicate the weed meets nutrient requirements.

This type of specific information is most useful for producers in developing weed control strategies that include livestock grazing.  This award was quite helpful in adding to the knowledge base about weed nutrient values in Oregon.  We look forward to completing the study this year.