Companies throughout the food chain are changing the way they do business in response to soaring grain costs, and consumers are likely to bear the brunt in the form of rising food prices.

Farmers are making the broadest cuts to their livestock herds in decades, meaning meat at the supermarket will likely cost more in coming years. Middlemen are trying to shorten the duration of supply contracts to 90 days from one year so they can pass on higher costs more quickly. And food brands are shrinking the contents of their packages,...