@porkpal there are a lot of similar plants, many are shrubby and a few, like this one, are annuals. I think nearly all of them are toxic to some degree or another to cattle. I think in this case the danger occurs when forage is poor and they eat the mature bean pods. It's sort of a circumstantial thing and not very common. Our drought corresponded with an increase in the number of these plants since they primarily grow in the dry river bed. Drought also results in poor forage which is exacerbated by the onset of winter and that leaves the mature pods exposed at the worst possible time. Toxic plant poisoning in livestock happens more often than people realize. It occurs especially in cattle when they are relocated to an unfamiliar grazing area with a different set of plants. I was pretty sure I would find this plant toxic for cattle, so I want to be aware. A lot of times an apparently healthy animal will die unexpectedly for unknown reasons. As the quote from the web page I quoted above says, the early symptoms are often not observed. Cattle are domesticated animals, but they aren't usually pets and close observation as with a pet doesn't usually happen. I'm not overly concerned, but I want the knowledge if it's available. Prussic acid poisoning, which is Hydrogen cyanide (HCN), is probably the most common one here usually from Johnson grass. It's very quick and very lethal. In wet years clover causes pasture bloat and that is also common here.
