Nitrate poisoning can be rapidly fatal with death occurring within three to four hours after ingestion of a fatal dose. I talked with the local Roswell Veterinarian, Dr. Leonard Blach, who said pigweed had been found knotted up in at least one of the hay bales which were three or four years old. Mr. Macias explained that he got one hundred bales of four year old hay free of charge not long ago. New Mexico growers say that if hay is stored correctly and covered well, it can last that long. But if it has pigweed or other nitrate-concentrating plants mixed in, nitrate concentration increases as the plants age.
Nitrate poisoning alters an animal's blood, blocking oxygen absorption.
So basically, cows suffocate. And according to the New Mexico veterinarians, that's what happened to half the herd in Marcello Macias's Roswell corral. All Rights Reserved.