Mark's stomach, or rather, stomachs, rumbled with hunger at the delicious smell coming from the trough. The other cows had already crowded around and were slurping away at the grain. Mark took two steps closer to the trough and bent his growing snout towards it.
What am I doing? Mark thought to himself. I'm not a cow! I have to resist; I've got to get back to those vials and become me again, before it's too late!
He fought his new bovine instincts and managed to take a step away from the trough. But as he took another step, the cow next to him shifted, and Mark's foot got tangled with the cow's. Mark fell forward, thrusting his arms out to catch himself before he hit his head on the side of the trough. He tried to push himself back up onto his legs, but found he felt much more comfortable standing on all fours. The trough was also right in front of his nose now, and the delicious aroma wafted straight to his new instincts.
His new, longer tongue darted out before Mark could stop himself and slurped up some of the grain. He chewed and swallowed, and found himself craving still more. The part of his mind that was still human screamed at his body to get away, that he needed to get to the vials, but his now rapidly changing cow body was far more interested in the grain. Mark lowered his snout into the trough, and soon was devouring the grain alongside the other cows.
As Mark ate, the transformation continued, bolstered by the hormones in the grain. He saw out of the corner of his eye that he was nearly as tall as the other cows now, and the cows on either side of him had shifted to accomodate his growing bulk. As Mark and the cows finished up what grain remained in the trough, the sound of the barn door opening reached his ears...