Poison hemlock is another weed we have. Being originally from the east coast, I made the assumption all those pretty plants were Queen Anne's Lace...wrong!!
It can be distinguished from the benign plants by the purple blotches on the stems.The stuff has been growning all over the yard and in the fields and I never really worried about it. Occasionally the horses would nibble a bit on it, but it never seemed to affect them. You can read about it in many placed, but I will just use the Merch Veterninary Manual.
To quote the online Merck manual the toxic principles and effects are:
"Piperidine alkaloids (coniine and others) in vegetative parts. Acute course. Dilated pupils; weakness; staggering gait; slow pulse, progressing to rapid and thready. Slow, irregular breathing; death from respiratory failure."
Symptoms include nervous trembling, dilated pupils, salivation and coordination problems usually in the hindquarters. Check for week pulse and look for a bluish appearance of gums and mouth tissue.
I have read that in serious cases death due to respiratory paralysis may occur within ten hours of the beginning of symptoms. There are treatments for less serious cases, and these may include stomach tubing with mineral oil and immediate use of stimulants.
The last dangerous weed we know we have is cockleburr. This week is something that I have tolerated, and every fall end up cleaning manes on the horses for hours on end. Sure, I run them down with the lawn mower when they are small, but still the manage to grow in places I just can't quite reach. So back to the online Merck manual, and what did I find:
"Carboxyatractyloside (seeds and young seedlings). Anorexia, depression, nausea, vomiting, weakness, rapid weak pulse, dyspnea, muscle spasms, convulsions. Lesions include GI inflammation, acute hepatitis, nephritis."
Okay so a lot of big words, but obvious not good for horses, so I started in on them as well. Well below is one little load of many that I ended up digging out, piling and burning. Yes, there are still more around the place, and it has become a daily chore. So you are probably thinking, why not use a herbicide to kill all this stuff? Really simple, I own peacocks and I don't want to kill them with the poision chemicals I would have to use. So excuse me for now, have an appointment with another load of weeds.