Abstract: Abstract: Weaned piglet's pellet feeds are designed for healthy growth of weaned piglet. Conditioning is a key factor affecting pellet feed quality and pellet mill throughput, which can be defined as the process of transforming the physical state of the mixed mash with the addition of saturated steam to facilitate the compaction of the feed mash. Knowledge of the thermal properties of mash feed is required to perform the heat transfer calculations that are involved in the optimal design of conditioner and evaluation of operating parameters. Specific heat is an important thermodynamic parameter used in heat transfer and energy balance calculations. Conditioning processing involves broad temperature (25-95 ℃) and moisture content (12%-16.5%, wet base) ranges. The objectives of this investigation were to determine the specific heat of mash feeds for weaned piglet as affected by moisture content, temperature and grinding particle size. In this work, the specific heat of mash feeds for weaned piglet in 4 grinding particle sizes (geometric mean diameter of 346.34, 364.57, 388.93 and 404.25 μm, and sieve aperture of Φ1.0, Φ1.5, Φ2.0 and Φ2.5 mm) was measured as a function of moisture content (10%-18%) and temperature (25-100 ℃) by differential scanning calorimetry (DSC). The mash feeds were processed in Xinsanfeng feed mill in Miyun District, Beijing, while the determination of specific heat was conducted in China Agriculture University from April to November in 2015. As for the experiment design, the method of total experiment with full randomization was applied with 3 factors which included 4 kinds of grinding particle sizes (346.34, 364.57, 388.93 and 404.25 μm), 16 levels of temperatures (25, 30, 35 , 40, 45, 50, 55, 60, 65, 70, 75, 80, 85, 90, 95 and 100 ℃) and 5 levels of moisture contents (10%, 12%, 14%, 16% and 18%). The influences of these variables on the specific heat were analyzed and a prediction model of specific heat concerning these variables was established. The specific heat was found to be significantly dependent on moisture content, temperature and grinding particle size, and the effect of moisture content was greater than the other 2 factors. In addition, the specific heat was proved to be significantly dependent on the interactions of moisture content and grinding particle size/temperature. Specific heat of mash feeds over 4 grinding particle sizes increased in the range of 1.572-2.747, 1.533-2.783, 1.562-2.869 and 1.548-2.881 kJ/kg·K with the increase in moisture content and temperature respectively. Specific heat had a linear positive correlation with moisture content and a logarithmic correlation with temperature. At 25 ℃ and 85 ℃, the specific heat values of mash feeds over 4 grinding particle sizes varied in the range of 1.533-2.037 and 2.289-2.758 kJ/kg·K with the increase of moisture content respectively. The specific heat of mash feeds with higher grinding particle size (404.25 and 388.93 μm) was greater than that with lower grinding particle size, especially at high temperature (60-100 ℃) and high moisture content (18%). As the grinding particle size of mash feed is reduced, the surface area is increased geometrically. So per unit weight of mash feed with lower particle size will condense more heat and water. This will result in the mash feed with lower particle size having higher degrees of starch gelatinization and protein denaturation. The variations in state and components of mash feeds may contribute to the differences in specific heat. Regression models with high R2 values were established to predict the specific heat of mash feeds as a function of 2 dependent terms of only moisture content and temperature, and of 3 dependent terms of moisture content, temperature and grinding particle size. The inclusion of grinding particle size dependent term in the empirical equation is expected to enhance the predictive capacity of model at high moisture contents in comparison with that equation only including moisture content and temperature. The results provide basic data for the establishment of the heat-transfer equation in conditioning of feeds for weaned piglet, and offer theoretical reference for the optimization of process parameters in thermo-processing.