We present a preliminary study of a wearable system to monitor biomarkers for dairy and suckling cattle. Finding the optimal location on the cow body (ears) and designing the adapted microneedles to reach the interstitial fluids underneath the cow skin are the two points addressed here.For the selection of the location, 4 breeds of suckling cows (Aubrac, Charolaise, Lim-ousine, Salers) and 3 breeds of dairy cows (Abondance, Montbe ⠁liarde, Holstein) were chosen. Measurements of the thickness of the ear tissues were conducted on three areas of the ear (top, apex and base of the pinna), on the external and internal sides. Results show that the apex of the pinna, external side, is the best area for microneedle implantation with an implantation window of 1403 +/- 589 mm (DeepDe), considering all breeds. To reach this implantation window located between the stratum corneum and the cartilage, the microneedle has to pass through 1323 +/- 404 mm of tissues (SupDe), considering all breeds. From these results, a microneedle design was made on SolidWorks. With a conical shape 2.89 mm in height and a conical channel 300 mm in diameter (at the tip of the microneedle), the model was made using 3D printing. The resulting microneedles respect the SolidWorks design with fair accuracy. They were connected to a microfluidic channel for sampling or releasing fluids.