Holly felt as if she was on fire, juices squelching from her vagina, she burned with lust, with each thrust Boris made she began to gain weight. First her shirt already damaged by Boris tore away under the strain of her growing girth, and soon after her ass ballooned out to match Grace's. Holly's new ass served to excite Boris, who pounded even harder than he had been doing, the movement shook Holly's stomach around, and pin pricks of pleasure signaled the new growth of teats along its length, no time was wasted as they quickly grew to full size, her original breasts morphing into matching teats, bra falling away as they did, Holly screamed in pleasure as all her teats bloated and began to leak milk.
Her changes did not stop there, and looking down Holly saw her hands and feet reshape into trotters, her arms and legs reforming into stumpy pig legs as they did. Her pleasure was increased ten fold as finally her vagina morphed into a sows, increasing her compatibility with Boris considerably. A tail erupted from above her ass accompanied by a spray of cum as Boris grunted and began to fill Holly with his seed. "Reeeeaaee, knock me up you stud!" Holly squealed, as her ears enlarged and reshaped, she snorted as she breathed in the cum filled air, her nose beginning to stretch into a snout.
As Boris continued to cum he showed no signs of running out, and Holly's belly began to expand, filling with gallons of semen. She grunted in pleasure as she finished transforming, now fully a sow she was compatible with the cum inside her, and was no doubt already pregnant. As Holly reached her final climax she squealed in ecstasy and collapsed to the ground, having fainted from the pleasure, Boris collapsed on top of her panting, his job complete.
When Holly finally awoke it was dawn, the night having passed, for a passing second she though it had all been a dream, but then she saw Grace asleep nearby, her belly huge and pregnant, she shifted to look down as best she could with her new form and saw her belly, easily twice the size of Grace's, the teats along it's length oozing milk, with her serum boosted reproduction, it would be mere days before she birthed her first litter. Though she retained her mind at first Holly thought she would probably have been better off losing it like Grace, though the growing sense of contentment she felt made her realize maybe she liked this. Perhaps being a breeding sow wouldn't be so bad after all.