This study aimed to evaluate the biological activity in blood serum plasma samples from mares at different reproductive stages using dynamic speckle analysis. For this purpose, samples were collected from 40 Mangalarga Machador mares from the Formoso 2S horse farm in Cajueiro, AL. The mares were classified into four groups of ten animals each according to the pregnancy stage: ten empty mares (not pregnant), ten pregnant mares in the early third of pregnancy between one month and four months, ten pregnant mares in the final third of the pregnancy between seven and eleven months, and ten lactating mares (within two months post-partum). The biological activity response using a dynamic speckle (biospeckle) was obtained by capturing images reflected by a coherent light (diode laser with a wavelength of 532 nm and intensity of 3 mW) on a sample using a CCD (charge coupled device) camera. This data was analyzed using image processing techniques through the computational application Speckle-THSP-MCO-Descritores (STMD), applying THSP (time history speckle pattern) methodology, which evaluates the temporal evolution of the interference image from spreading over the sample surface over time. A coherence matrix generated from the THSP was used to present the intensity module dispersion, which provided the bioactivity data. These data were then processed using the program OriginPro 8. Ink, generate graphs and compare the results from the different groups under study. A general biospeckle signature was observed regardless of the mares’ reproductive stage considered in this study. A short phase of movement of the samples associated with an accommodation of the drop on the slide was observed. It was followed by an ascending curve starting between 5 and 10 min of observation, reaching a peak within 15 and 25 min, and finally decayed uniformly until almost zero after 45 min. The group of pregnant mares in the final third of pregnancy presented superior bioactivity compared to pregnant mares in the early third of pregnancy. The curve observed for the group of lactating mares is similar to the curve obtained for the group of pregnant mares in the early third of pregnancy. Bioactive molecules act as dispersion elements of coherent light incident on a sample. The variation inherent to the presence of bioactive molecules in the different stages evaluated influenced the biospeckle pattern detected in each sample. It was concluded that the biological activity peaks of the blood plasma samples from the mares evaluated in this study using the dynamic speckle analysis technique were different for both amplitude and time of occurrence, according to the different reproductive stages.