As Mary slowly gets up and recovers from her fucking, in her daze she looks over at the mare leaving her behind. As she watched the mare head toward the other she was entranced by the balls and cock bobbing side to side. Standing there in a daze she felt cum continue to slide out of her gaping cunt, and her cock started to stir again with little life. As she watched the mare's cock drip and harden as the other mare was accepting the mount she noticed something. Being exposed to the cum the other mare was unaffected by the mare cock that was now being rammed into her. Just watching the really started to stir Mary's libido again and wanted her vagina filled again with the massive horse cock.
After a few more seconds bewildered that the other horse wasn't growing she decided to take matters into her own hands. Quickly she squatted down and soaked her hands in the puddle of her cum and the mare and rushed over to the fucking mares and got underneath the one being mounted. Watching the massive horse balls swinging back and forth as the cock rammed the cunt excited Mary so much she was acting on auto pilot. She placed her hands between the mares legs and wiped all her cum off onto the mares underside. A shrill loud whiny came out and Mary saw the formation of a giant bulge and growing skin. As fascinated as she was she turned quickly and positioned herself to receive the newly growing hard cock.
As soon as she did she felt a rod hit her backside she lifted just enough and quickly greeted with a massive girth penetrating her pussy. She then not only felt the cock growing inside her but the strength of the mare fucking her partner. Seconds later the new cock was hard and the new futa was naturally bucking her hips at the sensation of something on her cock. Mary was overcome with pleasure as the cock was driven into her cunt and deep into her body with a force that she never dreamed of. She pushed back with all her might but still her arms would buckle as she was thrust forward by the massive cock. She was overwhelmed again and soon felt the strongest thrust of all and the cum explode into her hungry cunt. Her gut swelled slightly as she stood pinned on the rod, as her body shuddered. Just as quickly as it happened she felt the cock dislodge from her cunt and she collapsed to the ground and passed out from exhaustion.