Despite Sales and Operations Planning (S&OP) is widely known in today's supply chain literature, its impact on supply chain's performance has been neglected. Furthermore, no research exists on mathematical modeling of S&OP in dairy industry. This study is going to investigate the benefits of S&OP using a mathematical modeling approach. Three novel Mixed Integer Programming models are presented to do so: a Fully Integrated S&OP (FI-S&OP) model, a Partially Integrated S&OP (PI-S&OP) model, and a decoupled planning (DP) model. All these models are developed for a multi-site manufacturing company, which is coping with various raw material suppliers and Third Party Logistics (3PLs), Distribution Centers (DCs), and customers with wide range of product families. Finally, all the models are applied in a real case in a dairy manufacturing company in Iran. The results demonstrate a slight superiority of FI-S&OP over PI-S&OP model and a strong domination over DP model. (C) 2017 Published by Elsevier Ltd.