A reliable method to measure presence and quantity of the toxic factor in needles of ponderosa pine (Pinus ponderosa Laws.) was developed using embryo implantation and gestation in laboratory mice as the basis of the assay. The abortiofacient factor was present in both aqueous and acetone extracts of ponderosa pine needles. Control animals had significantly (P<0.1) greater number of viable embryos at 124, 148, and 172 hr post-coitum than mice fed pine needle extracts. A gestation study verified results from the implantation experiment, as few mice fed pine needle extracts delivered normal litters. Frequently, mice receiving the concentrated aqueous extract had diarrhea and decreased feed intake. Failure of implantation by 124 hr postcoitum in bred mice fed aqueous or acetone extracts of ponderosa pine can be used as an index of the risk involved in grazing ponderosa pine ranges, but cannot be used to predict losses. This material was digitized as part of a cooperative project between the Society for Range Management and the University of Arizona Libraries. The Journal of Range Management archives are made available by the Society for Range Management and the University of Arizona Libraries. Contact lbry-journals@email.arizona.edu for further information. Migrated from OJS platform August 2020
Scholarly peer-reviewed articles published by the Society for Range Management. Access articles on a rolling-window basis from vol. 1, 1948 up to 5 years from the current year. Formerly Journal of Range Management (JRM). More recent content is available by subscription from SRM.