Pine needle abortion in cattle: a review and report of 1973-1984 research.

Research has verified field observations that cows grazing ponderosa pine needles may abort. The incidence and nature of the abortions produced experimentally simulate very closely those reported by livestock producers and veterinarians. The incidence of experimentally-produced abortions varied markedly from year to year even though the needles were collected in the same general area each year. This suggests that the abortifacient compound(s) in the needles vary from year to year, probably due to environmental and site conditions. The impact of stress (cold and nutrition) as a factor in the abortions was examined. It was concluded that the only effects would be on the willingness of cows to eat the needles. The pine needle abortion problem, what is known of the etiology, and mechanisms of the abortion are reviewed. The usefulness of bioassay systems to study pine needle abortions is discussed.