They altered their diet to boost a nutrient that they were missing and the new diet was lacking in far more important nutrients that the zebras really needed. I think I heard that they actually froze to death or something weird because the nutrients missing from their new diet were needed to keep sufficient fat on their bodies. But I might be mistaken because an elephant and some other animals died over the past few years due to mishandling of their diets. The story on the Post site says the zebras died of malnutrition and hypothermia. See the fifth paragraph from the bottom.
Duh!! The zoo is run by the federal government!! The people who are employees of the zoo are federal employees and union memebers. Does that answer your question?