Wireless Body Area Networks (WBANs) provide promising applications in the healthcare monitoring of dairy cows. The characterization of the path loss between on-body nodes constitutes an important step in the deployment of a WBAN. In this paper, the path loss between nodes placed on the body of a dairy cow was determined at 2.45 GHz. FDTD simulations with two half-wavelength dipoles placed 20 mm above a cow model were performed using a 3-D electromagnetic solver. Measurements were conducted on a live cow to validate the simulation results. Excellent agreement between measurements and simulations was achieved and the obtained path loss values as a function of the transmitter-receiver separation were well fitted by a lognormal path loss model with a path loss exponent of 3.1 and a path loss at reference distance (10 cm) of 44 dB. As an application, the packet error rate and the energy efficiency of different WBAN topologies for dairy cows (i.e., single-hop, multi-hop, and cooperative networks) were investigated. The analysis results revealed that exploiting multi-hop and cooperative communication schemes decreases the packet error rate and increases the optimal payload packet size. The analysis results revealed that exploiting multi-hop and cooperative communication schemes increases the optimal payload packet size and improves the energy efficiency by 30%.