Introduction: Information asymmetry within the supply chain leads to numerous challenges, particularly in the chains involving perishable products such as dairy. If a third-party logistics (3PL) provider fails to communicate demand information to the manufacturer in a timely manner, it compromises both the manufacturer's planning and the performance of other supply chain actors. Furthermore, under such conditions, the manufacturer would be unable to respond effectively to market changes. So in this study, a new contract has been developed which is designed considering demand information delivery time. Through this contract, the third-party logistics (3PL) provider company is required to share demand information within a predetermined timeframe agreed upon with the manufacturer; otherwise the third-party logistics (3PL) provider company should pay penalties to the manufacturer. This mechanism results to reduce the impact of information asymmetry in the chain and enhance the overall performance of the supply chain than before.

Methods: A four-echelon model for perishable dairy products has been considered in this research, which includes the government, the dairy manufacturer (Pak Company), the retailer, and a third-party logistics (3PL) provider company; so that the demand function is modeled as a function of both price (incorporating both direct effects of retail price and the effects of government subsidy) and the level of efforts to make freshness. A Stackelberg game model is employed, in which the government acts as the overall supply chain policymaker and the manufacturer and the third-party logistics (3PL) provider company are considered as the internal supply chain leaders under different scenarios and at the same time, the retailer is given as the follower in all scenarios. The Pak Dairy Company has been selected as a case study and it should be noted that the data used in this study were collected from this company and also validated based on expert opinions of the company’s experts.

Results: The results of the data analysis demonstrate that designing an information-sharing contract between the manufacturer and the third-party logistics (3PL) provider company is effective to mitigate demand-related information asymmetry within the chain and maximize the profit of all stakeholders, whenever the subsidy is granted to the retailer and the manufacturer is considered as the leader of internal chain. When the subsidy is given to the retailer, the retailer also strives more efforts toward product freshness; these efforts are tangible to consumers and consequently drive an increase in demand. Meanwhile, as the manufacturer is the chain leader, the freshness-related efforts by the third-party logistics (3PL) provider company are effectively managed by the manufacturer. Conversely, if the third-party logistics (3PL) provider company is the chain leader, it will make fewer efforts towards the product freshness and may also potentially provide misleading reports to attract the attention of the other players in the chain about its efforts to keep the product fresh.

Conclusion: Based on the findings of this study, the manufacturer-led scenario, combined with government subsidies to retailers for their efforts in product freshness, yields the best performance among all evaluated scenarios. Furthermore, if the time of information-sharing between the third-party logistics (3PL) provider company and the manufacturer is determined to be less than 2.5 days, the total profit for all stakeholders is maximized. Under these conditions, the supply chain achieves superior performance compared to the current state of the company, and the impact of information asymmetry within the chain is significantly mitigated.