Toxicological Trivia from February 09. 2010: A wide variety of forage species and weeds have the ability to accumulate nitrate. Among nitrate accumulating weeds and associated  cases of ruminanrs toxicity,  with which of the following plant of the picture could occur:
a) Sorghum Aleppo;
b) Red weed;
c) Giant thistle.

Correct answer c. The scientific name is Silybum marianum. Read mores in Spanish article: Nitrates in plants eaten by ruminants