Complex sentence: Many grocery stores and supermarkets, including the nation's three largest chains, announced that they would no longer sell products containing the additive, while some grocery companies, restaurants and school districts discontinued the sale and provision of beef containing the additive after the media reports.
Split into simpler sentences: Many grocery stores and supermarkets, including the nation's three largest chains, announced that they would no longer sell products containing the additive. Some grocery companies, restaurants and school districts discontinued the sale and provision of beef containing the additive after the media reports.