He made a proclamation and published through Nineveh by the decree of the king and his nobles, saying, "Let neither man nor animal, herd nor flock, taste anything; let them not feed, nor drink water;
What a bellowing must have gone up to God when none of the cattle were watered or fed.  Anyone who ever witnessed the lowing of thirsty cattle can never forget the terrible impact of it.  This action initiated by the king was evidently designed to achieve just such an impact upon the whole population.  The king's decree is continued in the next verse.