As Jeff's mouth remained plastered on Sarah's udder, he felt a tingle throughout his body. Sarah was mooing intensely; neither of them cared if Natalie woke up. She filled Jeff's mouth with milk, him savoring every drop.
Jeff was completely transfixed on her milk; he didn't notice the four nubs growing out of his stomach. His belly expanded from Sarah's milk, the skin turning pink and fleshy as his new teats continued to grow longer. At the same time, his penis started shrinking, and all the cum in his testicles shot out of him as his balls receded. His new udder covered his shrinking penis, whose scrotum had become a vaginal opening. Jeff's now tiny cock continued to shrink, until it became his new clit. His udder began to leak milk onto the floor, as horns protruded from his head.
Opening her eyes, Sarah saw her boyfriend's horns, and looking down, his fat pink udder. She gasped.
'Jeff, wait! You're changing,' she said, touching Jeff's horns. Jeff looked down, surprised to see a fleshy mass resting on his cow-like legs.
'What the hell?' He said. Jeff touched his new udder, and it shot milk out onto Sarah's chest, making Jeff moo. He covered his mouth, eyes wide.
'It looks like my milk made you a cow too,' she giggled. Jeff felt an unfamiliar void between his legs. He pulled his udder up, finding nothing but a thin slit where his cock once was.
'Oh my god,' he said, as he touched his new pussy lips, sending a jolt up his spine. He got up, stumbling for a second as his new udder changed his center of gravity. Jeff looked in the full body mirror to inspect his new form. He looked the same as before, except with a heavy, leaking udder on his stomach, and a dampening pussy between his thighs. He lifted his legs, only to find that his feet had been replaced by cow's hooves.
Sarah came up behind Jeff, grabbing his new teats.
'I think you look good like this, babe,' Sarah said, milking her boyfriend's overflowing udder. He mooed loudly as his teats shot milk onto the mirror's reflective surface. Jeff's pussy became dripping wet; Sarah inserted a finger inside, making Jeff's legs weak. Sarah moved between his legs, eating out his pussy as his udder covered her eyes.
Jeff climaxed, experiencing his first female orgasm. He would have collapsed, if it weren't for his girlfriend, who caught him and kissed his face with her cow-like muzzle.
As they lay in each other's arms, they began to discuss what they should do next.