I haven't studied vertical integration and its consequences in the food industry, but I've certainly studied it. In fact, I teach it. I just did my class on this.
With vertical integration in major economies—mostly in the States—the trend is towards de-integration because of market forces, and I don't have time to go into all the reasons. The reason we have so much vertical integration in agri-food in Canada, I think, is the lack of competition. It has sheltered companies and allowed them to vertically integrate, and I think it's fair to say that the research shows that companies that are vertically integrated are able to impose more market discipline and control over prices and to make more money.
Ideally, I think we want to encourage de-integration, whereby a firm will sell off its subsidiaries that are upstream more than the downstream ones.