Grazing management effects on sediment, phosphorus, and pathogen loading of streams in cool-season grass pastures.

Erosion and runoff from pastures may lead to degradation of surface water. A 2-yr grazing study was conducted to quantify the effects of grazing management on sediment, phosphorus (P), and pathogen loading of streams in cool-season grass pastures. Six adjoining 12.1-ha pastures bisected by a stream in central Iowa were divided into three treatments: continuous stocking with unrestricted stream access (CSU), continuous stocking with restricted stream access (CSR), and rotational stocking (RS). Rainfall simulations on stream banks resulted in greater ( < 0.10) proportions of applied precipitation and amounts of sediment and P transported in runoff from bare sites than from vegetated sites across grazing treatments. Similar differences were observed comparing vegetated sites in CSU and RS pastures with vegetated sites in CSR pastures. Bovine enterovirus was shed by an average of 24.3% of cows during the study period and was collected in the runoff of 8.3 and 16.7% of runoff simulations on bare sites in CSU pastures in June and October of 2008, respectively, and from 8.3% of runoff simulations on vegetated sites in CSU pastures in April 2009. Fecal pathogens (bovine coronavirus [BCV], bovine rotavirus group A, and O157:H7) shed or detected in runoff were almost nonexistent; only BCV was detected in feces of one cow in August of 2008. Erosion of cut-banks was the greatest contributor of sediment and P loading to the stream; contributions from surface runoff and grazing animals were considerably less and were minimized by grazing management practices that reduced congregation of cattle by pasture streams.

Pine needle abortion biomarker detected in bovine fetal fluids.

Pine needle abortion is a naturally occurring condition in free-range cattle caused by the consumption of pine needles from select species of cypress, juniper, pine, and spruce trees. Confirmatory diagnosis of pine needle abortion has previously relied on a combined case history of pine needle consumption and detection of isocupressic acid in a sample from the dam. Stable metabolites of isocupressic acid include agathic acid, dihydroagathic acid, and tetrahydroagathic acid, which have been shown to be present in the serum of mature animals for a few days following consumption of pine needles. As maternal serum is infrequently submitted for diagnosis of cattle abortions, a diagnostic assay capable of confirming isocupressic acid exposure in other matrices would be desirable. To the authors' knowledge, no previous investigations have indicated whether these stable metabolites of isocupressic acid cross the placenta or are detectable in fetal tissues. Therefore, the presence of agathic acid, dihydroagathic acid, and tetrahydroagathic acid was evaluated using gas chromatography-mass spectroscopy on fetal thoracic fluid and stomach contents collected from 2 aborted bovine fetuses with a recent herd history of pine needle consumption by the dams and a subsequent abortion outbreak in the herd. Only tetrahydroagathic acid was detected in the fetal thoracic fluid and fetal stomach contents. The current study encourages diagnosticians to collect fetal thoracic fluids to permit the detection of tetrahydroagathic acid in cases of suspected pine needle abortion.