Fatty acid (FA) supplements are widely used in lactating cow diets to increase energy intake. Previous published research has reported that supplements with moderate enrichment (~85%) of palmitic acid have expected digestibility, while very high enrichments (~98%) have lower digestibility. Saturated FA have the potential to form organized secondary structures at high purity. Differential scanning calorimetry (DSC) is a thermal technique commonly used in material science to measure the change in heat flow as energy is absorbed or released from a sample during heating. Our hypothesis was that a supplement with a very high enrichment would differ in physical characteristics due to the formation of a secondary structure, which may contribute to a decreased digestibility. A 98% stearic acid (SA; 98.5% C18:0, 0.4% C16:0), 98% palmitic acid (PA; 98.5% C16:0, 0.7% C18:0), and a mixture of palmitic and stearic (PA/SA; 54.5% C16:0, 44.5% C18:0) sample were used for this characterization. Sample FA profile was determined by gas chromatography with a flame ionization detector. Data from DSC was gathered on a Q600 SDT (TA Instruments). Briefly, ~40 mg of sample was heated at 5°C/min from 25°C to 110°C. TA Universal Analysis software (TA Instruments) was used to determine melting temperature, and total enthalpy of melting (area under the curve). Triplicate runs were highly reproducible. Melting temperature of the PA/SA mixture was 61.2°C, similar to the reported melting temperature of PA (62.9°C). However, the melting temperatures of the high purity PA and SA were increased to 67.8°C and 73.7°C, respectively. The enthalpy of melting was increased 12.5% in the high purity PA compared with the PA/SA blend. Melting enthalpy for the high purity SA supplement was increased 3.5% from the high purity PA and 16.4% from PA/SA mixture. Although melting temperatures are well above body temperature, increasing the energy required to melt the sample is indicative of physical characteristics of the supplement expected to decrease digestibility.