Dr. Elena Voss slammed her apartment door shut after a grueling twelve-hour shift at the pharmaceutical lab. At thirty, the single biochemist had poured her career into developing a new blood pressure medication, a potent vasodilator that relaxed smooth muscles with ruthless efficiency. Her white lab coat, slung over her arm, felt heavier than usual. She tossed it onto the kitchen counter, not noticing the faint rattle from the pocket where a few stray sample pills had tumbled in during a rushed meeting.
Rex, her sleek black Doberman, bounded in from the living room, his muscular frame rippling under short fur. The dog nosed at the counter, tongue lolling as the pills spilled out with a soft clatter. He snatched them up in one gulp, crunching them like his usual treats, tail wagging furiously. Elena barely glanced over, kicking off her heels. "Good boy, Rex. Mommy's home."
She showered quickly, the hot water easing the ache in her athletic legs from hours on her feet. Her body stayed toned from weekend runs and gym sessions, her 32D breasts firm against the steam-fogged glass. Dressed in a loose tank top and yoga pants, she flopped onto the couch with a glass of wine, scrolling her phone. Rex paced nearby, whining softly.
An hour later, a low growl pulled her attention. Rex lay on the floor, hind legs splayed, his sheath swollen and exposed. A thick, red rocket of a cock protruded fully, nine inches long and veined, the tip tapered and glistening with precum. At its base, a bulbous knot throbbed, three inches wide, pulsing with unnatural vigor. The pills. Fuck, the vasodilator had hit him hard, flooding his system with relentless blood flow, trapping that erection in overdrive.
Elena's stomach twisted. The vet? No way. "My dog ate experimental boner pills and now his dick won't go down"? She'd lose custody, face questions, maybe lab audits. Her cheeks burned at the thought. Rex whined again, humping the air, his massive cock slapping against his belly with wet smacks. She couldn't leave him like this. Heart pounding, she coaxed him to her bedroom. "Easy, boy. Mama's gonna fix it."
She guided the hundred-pound Doberman onto her king-sized bed, pushing his shoulders until he rolled onto his back, legs akimbo. His cock jutted straight up, hot and slick, the knot inflating further under her gaze. The musky scent hit her first, sharp and animalistic, mixing with the faint chemical tang of his saliva. Elena knelt between his thighs, her small hand wrapping around the shaft. It burned against her palm, velvet skin over steel hardness, veins throbbing like live wires.
She stroked slowly at first, base to tip, twisting her wrist on the upstroke. Precum oozed from the pointed head, slicking her fingers. Rex panted, hips twitching, but after five minutes, nothing. The drug's endurance boost kept him rigid, unyielding. Her arm ached. "Come on, boy," she muttered, pumping faster. The shaft pulsed, but no release. Sweat beaded on her forehead. This wasn't working.
Desperation clawed at her. She leaned down, breath ghosting the flared tip. The smell intensified, pungent and feral, stirring something dark in her gut. She parted her lips, tongue flicking out to taste the salty bead of precum. Bitter, thick. She hated it, the wrongness of it twisting her insides. But Rex's cock twitched, and a forbidden heat bloomed between her legs. Her pussy clenched, dampening her panties.
Elena took the head into her mouth, lips stretching around the girth. The heat seared her tongue, the flavor overwhelming her senses. She sucked tentatively, cheeks hollowing, then bobbed deeper. Inch by inch, the cock filled her mouth, pressing her tongue flat. She gagged as it hit her throat, saliva drooling down the shaft, but the sensation sparked electricity in her core. Her clit throbbed, nipples hardening against her tank top. She hated how good it felt, the fullness, the dog's helpless whines turning to guttural rumbles.
Her head moved with rhythm now, sucking hard on the upstroke, tongue swirling the underside. She went deeper, forcing past her gag reflex, nose burying in the musky fur at his sheath. The cock shuddered, twitching violently, but held firm. Precum flooded her throat, forcing her to swallow around the invasion. Gagging turned to moans, her free hand slipping into her pants to rub her soaked pussy. Wet folds parted under her fingers, clit swollen and slick. She loved it now, the degradation fueling her arousal, her throat milking that massive dog cock like a vice.
Still, no cum. Rex's endurance mocked her, his knot swelling bigger, balls tight but unrelenting. Elena pulled off with a gasp, strings of spit connecting her lips to the glistening red meat. Her body burned. She needed more. Stripping off her tank and pants, she revealed her athletic frame, toned abs flexing, full 32D tits bouncing free, pink nipples erect. Panties last, her shaved pussy glistened, lips puffy and dripping.
She straddled Rex cowgirl-style, knees sinking into the mattress on either side of his hips. Grabbing his cock, she aligned the pointed tip with her entrance. "That's it, boy. Fuck your mama's pussy." She sank down slowly, cunt stretching around the girth. Inch after burning inch split her open, the veins dragging against her walls. She gasped at the fullness, her juices coating him, dripping down to lube the knot. Bottomed out, she rocked her hips, grinding her clit against his sheath.
Rex bucked instinctively, fast and brutal. She guided him with her hands on his chest fur. "Hump me, Rex. Give it to me hard." He did, pistoning up with jackhammer force, cock slamming her cervix. Her tits jiggled wildly, pussy clenching in waves. Orgasm hit fast, her walls spasming, cream gushing around his shaft. "Fuck, yes! Cumming on your dog dick!" But he kept going, faster, her athletic body glistening with sweat, scent of her arousal thick in the air.
She came again, thighs quivering, nails digging into his fur. Third orgasm ripped through her, vision blurring, pussy squirting onto his belly. Still hard. Breath ragged, she lifted off, pussy gaping and red. "Not done yet, big boy. My ass needs that monster cock." She scooped her own cum as lube, slathering his shaft, then positioned the tip at her tight asshole. "Look at this endurance, Rex. Nine inches of perfect dog cock, knot like a fist. And these tits? Thirty-two D's just for you, bouncing while you wreck my shithole."
She pushed back, sphincter yielding with a pop. Pain flared, then pleasure as he filled her bowels, thicker than anything human. Rex thrust wildly, balls slapping her pussy. She rode reverse cowgirl now, ass cheeks spreading wide, the dirty slide audible over her moans. "Fuck my ass, you stud! Pound it!" Her hand mauled her tits, pinching nipples, dirty words spilling. The friction built, her hole gripping like a glove. Rex growled, hips blurring. Heat bloomed deep, his cock swelling, then erupting. Thick ropes of dog cum blasted into her guts, hot and endless, filling her until it leaked out in creamy rivulets.
Fifteen minutes later, he slipped free, ass prolapsed slightly, cum pouring onto the sheets in heavy globs. But his cock stayed rock-hard, knot throbbing, ready. Elena's eyes glazed with hunger. She wanted it all. Flipping to missionary, legs spread wide, she pulled him over her. "Breed me now, Rex. Knot your mama's pussy."
His tip speared her folds, plunging deep in one thrust. She wrapped legs around his haunches, heels digging in. He fucked like a machine, knot battering her entrance with each slam. Her pussy stretched obscenely, walls rippling, clit grinding his fur. Sweat-slick tits heaved, nipples rasped by his chest hair. "Deeper, boy! Fill me with that cum!" Sensations overwhelmed: the wet squelch of penetration, salty tang on her lips from earlier, his hot breath on her neck.
Ten minutes of relentless pounding, and he came. The knot forced in with a painful pop, sealing her tight. Cum jetted in powerful spurts, bloating her belly, pressure building as her pussy milked every drop. She orgasmed around the lock, convulsing, squirting past the seal. Twenty minutes they stayed tied, his cock pulsing inside her, her fingers circling her clit through aftershocks. Rex panted atop her, finally spent, but Elena lay there, filled and claimed, the forbidden high lingering in every throb.
Elena lay there for a long minute, chest heaving, every muscle trembling from the marathon of orgasms. Cum still leaked steadily from her gaping pussy and ass, thick white trails cooling on her thighs. Rex panted beside her, tongue lolling, his red cock finally starting to soften at the tip but still mostly rigid, knot half-deflated yet twitching with residual drug-fueled life. The vasodilator's grip was loosening, but not fast enough for her liking. She wanted control now, wanted to wring every last drop out of him before the high faded completely.
She sat up slowly, legs shaky, and grabbed the leather leash from the nightstand. "Come here, big boy. Time to make this easy." She coaxed Rex onto his back again, this time looping the leash around one of the sturdy wooden bedposts at the headboard. She tied it short, securing his collar so he couldn't roll away or lunge too far. His paws flailed a bit in confusion, but he stayed put, cock jutting up vulnerably, still glistening with her juices and his own cum.
Elena straddled him reverse now, facing his head so she could watch his reactions. She grabbed the base of his shaft, slick and hot, and sank down in one smooth motion. Her pussy swallowed him easily after all the stretching, walls fluttering around the familiar girth. "Fuck yes, that's my good stud. Mama's gonna ride this dog dick until you give me everything left in those heavy balls."
She rolled her hips in slow, grinding circles at first, clit dragging against his sheath fur with every rotation. Her full tits bounced heavily as she picked up speed, hands braced on his chest for leverage. "Look at you, tied up like my personal fuck toy. Nine inches of perfect red meat just for my greedy cunt. You love filling me, don't you? Love pumping all that thick cum deep where it belongs."
Dirty words spilled out faster, voice husky and wrecked. "God, your knot feels so good bumping my cervix. Stretch me wider, boy. Make my pussy gape for days." She lifted almost off him, then slammed back down, ass cheeks clapping against his hips. Sweat slicked her skin, tits jiggling wildly. She pinched her own nipples hard, twisting until pain sparked fresh heat in her core. "Cum for me soon, Rex. I want to feel you throb and flood my throat next."
After a few minutes of brutal riding, she pulled off abruptly, pussy clenching on nothing, dripping strings of mixed fluids onto his belly. She scooted down between his spread hind legs, mouth watering at the sight of his cock bobbing, still rock-hard but starting to leak less precum. The drug was definitely wearing off now; his endurance was cracking.
She wrapped her lips around the pointed tip and sucked hard, tongue swirling the underside. "Mmm, taste us together, boy. All that cum you pumped into my holes mixed with my pussy juice. So fucking filthy." She bobbed deep, throat opening easily after earlier abuse, nose pressing into his sheath. One hand cupped his heavy balls, rolling them gently while she hollowed her cheeks.
Rex whined, hips twitching against the restraint. In under five minutes his body tensed. Elena felt the first powerful spurt hit the back of her throat, thick and hot. She swallowed greedily, moaning around his shaft as rope after rope flooded her mouth. "Yes! Give it to me, stud. Cum down mama's throat like the good breeding dog you are." She milked him with her lips and tongue until he shuddered through the last weak pulses, finally spent in her mouth. She pulled off slowly, letting the last dribble coat her tongue before swallowing with an exaggerated gulp.
His cock softened noticeably now, knot shrinking fast, red length retreating toward the sheath. But Elena wasn't ready to end it. A wicked idea sparked, one she'd used on an ex years ago. That guy had gone rock-hard again after she rimmed him, begging for round two. If it worked on a man, why not on her beast?
She leaned lower, tongue flicking out to lap at his heavy balls, salty and musky. "These big balls worked so hard for me tonight. Time to worship them properly." She sucked one into her mouth, rolling it gently with her tongue, then the other, humming vibrations through the sensitive skin. Her hand wrapped around his softening shaft, stroking slowly from base to tip, coaxing life back into it.
Rex panted harder, tail thumping weakly against the mattress. She felt him twitch in her palm, thickening again under the dual assault. Emboldened, she pushed his hind legs wider with her free hand. Her tongue traced lower, past the base of his balls, until it circled the tight pucker of his ass. The taste was raw, earthy, animal. Filthy thoughts flooded her mind: this is so wrong, so depraved, licking my dog's asshole like a desperate slut. And fuck, I love it.
She pressed her tongue flat against the ring, then pointed it, pushing inside slowly. Rex yelped in surprise, then settled into low, rumbling growls of pleasure, hips bucking slightly. "That's it, boy. Feel mama's tongue in your tight little ass. You love being rimmed, don't you? Makes that cock wake right back up."
She worked her tongue deeper, in and out, while her hand stroked his shaft faster now, slick with leftover cum and spit. His cock hardened fully in her grip, knot swelling again at the base. The combination drove him wild; he whined and thrust into her fist, ass clenching around her invading tongue.
In less than three minutes he tensed again. Thick spurts erupted from his tip, splattering her cheek, chin, and tits in hot ropes. Elena kept stroking through it, milking every drop while her tongue stayed buried, feeling his hole pulse rhythmically. "Cum for me again, you filthy stud. Cover your mama in it."
When the last spurt faded, his cock finally shrank completely, slipping back into the sheath, knot gone for good. Rex lay there panting, eyes half-lidded, completely drained.
Elena sat back on her heels, face and chest streaked with cum, body aching in the best way. She wiped a glob from her nipple and sucked it off her finger, smiling lazily. "Good boy. All better now. But don't think this is the last time, Rex. Next time mommy brings home more samples... we're going even longer."
She untied the leash, curled up beside him, one hand resting possessively on his sheath as they both drifted toward exhausted sleep.
Two months had passed since the night Rex accidentally swallowed the prototype vasodilator.
Dr. Elena Voss no longer pretended this was an accident.
The 30 year old vascular biochemist stood in her home laboratory at 11:47 p.m., wearing nothing but an open white lab coat that barely covered her full breasts and left her shaved pussy completely exposed. Her long blonde hair was tied in a loose ponytail that swayed as she moved. The workbench was covered with neatly labeled blister packs and small amber bottles. Her private collection of custom formulations.
She had been busy.
Pill A: Enhanced vasodilator. Longer duration, moderate knot inflation.
Pill B: Potency plus seminal volume booster. Thicker, heavier loads.
Pill C: Combined hyper relaxant. Slower swelling but extreme endurance.
Pill D: Her latest. Knotlock 9. Aggressive blood flow plus delayed deflation. She was particularly proud of D.
Elena picked up two capsules. One B and one D. She crushed them into a small dish of wet dog food, the sharp chemical scent mixing with the meaty aroma. She watched Rex, her sleek black Doberman, eagerly devour the mixture from his bowl, his powerful tongue lapping noisily. Her pulse quickened with clinical anticipation and something far less professional. Heat was already pooling between her thighs.
"Good boy," she murmured, stroking his sleek head as he licked the bowl clean. "Tonight we will test the oral protocol first."
She led him into the living room and sank down onto the wide leather couch, spreading her long legs wide. Her slick pink folds glistened under the soft lamp light. Rex needed no further invitation. The moment she patted her thigh he jumped up, front paws on the cushions, his muscular body looming over her, warm fur brushing her sensitive skin.
Elena leaned forward, green eyes gleaming with hunger. She started slow. Exactly the way she liked it now.
Her fingers gently coaxed his sheath, stroking the emerging red tip until the full length slid out, hot and slick, veins pulsing visibly. She wrapped her soft lips around the tapered head, sucking softly at first, then deeper, letting her tongue swirl around the sensitive shaft. The salty, musky taste flooded her mouth and made her thighs clench with raw anticipation. She moaned around his cock, the vibration traveling straight down his throbbing length.
Rex panted heavily above her, hot breath washing over her blonde hair, hips twitching as she worked him with practiced skill. Elena took him further into her warm, wet mouth, cheeks hollowing, one hand massaging the slowly swelling knot at the base while the other stroked his firm belly. Drool began to drip down her chin as she bobbed her head, sucking noisily, savoring every inch of his growing dog cock.
She spent long minutes like this. Sucking, licking, occasionally pulling off to kiss and lap at the growing knot with wet, sloppy strokes of her tongue, whispering filthy observations between breaths.
"Already responding faster. Pill B is definitely increasing pre ejaculate volume. Mmm, look at you leaking for mommy already."
When his knot had grown to a solid fist size, shiny and swollen, and his shaft was throbbing angrily with need, Elena finally pulled back. Thick strings of saliva connected her swollen lips to his glistening red cock.
"Enough foreplay," she said, voice husky and dripping with lust. "Time for the main test."
She turned around on the couch, climbed on top of him in cowgirl position, and slowly sank down, guiding the thick, chemically enhanced cock into her dripping, eager pussy. The stretch was immediate and perfect, her slick walls parting around his hot girth with a wet squelch. She rode him with deliberate, rolling hips, feeling every vein and ridge drag along her inner walls. Leaning forward, she captured his long, slobbery tongue in her mouth again.
The tongue sucking had become her favorite part.
Elena sucked greedily on Rex's warm, wet tongue while she bounced, blonde hair swaying wildly, her full breasts pressing and jiggling against his furry chest. The pills were working beautifully. The knot swelled faster than ever. Thick, hot, and unyielding. Locking deep inside her with a loud, wet pop that made her gasp sharply into his mouth.
"Fuck yes, Rex. Look at that fat knot stretching mommy open so wide. You are such a good boy for me. Keep swelling, baby. Stretch mommy's tight cunt until I can't think."
She ground down harder, voice growing breathier and dirtier with every bounce, her words spilling out between messy tongue kisses.
"Come on, big boy. Swell up bigger for mommy. I want to feel you lock me so tight I cannot even move. That is it. Good dog. Fill mommy's greedy pussy with that huge throbbing knot. You love breeding your owner, don't you? Pumping all that hot cum deep inside me while I ride you like a desperate slut."
Elena's dirty talk flowed naturally now, low and filthy, right against his muzzle as she sucked harder on his drooling tongue between sentences, saliva running down her chin and onto her bouncing tits.
"Yes, just like that. Pound mommy from below. Make me your bitch. I can feel you getting even bigger inside me. Fuck, it is so deep. You are going to make mommy cum all over your big dog cock."
The tie lasted longer this time. The combination of pills kept the knot inflated for nearly an hour and a half. Elena came three times during the extended ride. Once from the initial lock, her walls clamping down hard around the massive bulge. Once from the relentless internal pressure grinding against her g spot. And once from the slow, grinding overstimulation while tied, her body shaking uncontrollably.
When Rex finally erupted, the load was massive. Thick, heavy ropes of hot dog cum blasted against her cervix in powerful jets, filling her so completely that her lower belly visibly swelled outward. Creamy white overflow squirted out around the massive knot in messy, rhythmic pulses, soaking the couch beneath them and running down her thighs in sticky rivers.
Elena stayed impaled, trembling violently, still lazily sucking on Rex's tongue even as the aftershocks rolled through her. Her scientific brain tried to take notes, but the words kept dissolving into soft, broken whimpers of pure pleasure.
After another twenty minutes, when the knot had only slightly deflated, she whispered against his muzzle, voice hoarse and satisfied.
"Tomorrow we try triple dose of D with a new oral enhancer. For science."
Rex gave a contented huff, his knot giving one final possessive throb inside her.
Elena smiled faintly, already thinking about the next formulation, her body still buzzing with the afterglow of being so thoroughly used.
Experimental Knot – Part 5: Oral Protocol
The next evening arrived faster than Elena expected.
Dr. Elena Voss stood once again in her dimly lit living room, completely naked this time, her white lab coat tossed carelessly over the arm of the couch. Her long blonde hair hung loose around her shoulders, a few strands already sticking to her flushed skin. On the coffee table sat three crushed capsules of Knotlock 9 and a small blue pill she had finished developing that afternoon. Oral Enhancer Alpha. It was designed to dramatically increase saliva production, heighten sensitivity in the canine tongue and shaft, and amplify the dog's urge to thrust without triggering full knot inflation.
She wanted control tonight. She wanted to focus purely on the oral side.
Rex watched her with eager, dark eyes as she mixed the pills into his favorite wet food. The moment the bowl hit the floor he attacked it, powerful jaws crunching and lapping until every trace was gone. Elena's heart raced as she knelt on the soft rug in front of the couch, her full breasts swaying gently with the movement.
"Come here, baby," she purred, patting her thighs. "Mommy has a special treat for you tonight."
Rex padded over immediately, his sleek black body towering above her as he stood. Elena reached up and gently coaxed his sheath with both hands, stroking slowly and firmly. The red tip emerged quickly, already glistening. She leaned in, warm breath washing over the sensitive flesh.
"That is it, good boy. Get nice and hard for mommy."
She started with soft, teasing kisses along the tapered head, then opened her mouth and took him in. Her lips stretched around the hot, smooth shaft as she sucked gently at first, tongue swirling in slow circles. The taste was strong and musky, sending a fresh wave of heat straight to her core. She moaned deeply around him, the vibration making Rex's hips jerk forward.
"Mmm… you taste so fucking good tonight," she whispered, pulling off just enough to speak before diving back down. "Mommy loves sucking her big dog cock. Look at you twitching already."
Elena worked him with practiced hunger. She bobbed her head steadily, taking more of his length into her warm, wet mouth with each pass. Drool poured freely from the corners of her lips, dripping down her chin and onto her heaving breasts. She used one hand to stroke the base of his shaft while the other gently massaged his heavy balls, feeling them tighten under her touch.
Rex panted loudly above her, hot breath ruffling her blonde hair. His hips began to thrust in short, instinctive pumps, fucking her mouth with growing urgency. Elena welcomed it, relaxing her throat and letting him slide deeper until the tip bumped the back of her mouth. She gagged softly but kept going, eyes watering with pleasure as thick strings of saliva stretched from her lips every time she pulled back.
"Fuck yes, Rex. Use mommy's mouth. Thrust into my throat like the horny dog you are," she gasped between sloppy strokes, her voice thick and filthy. "You love face fucking your owner, don't you? Getting all that warm drool all over your cock while I suck you dry."
She sucked harder, cheeks hollowing, tongue pressing flat against the underside of his shaft. The Oral Enhancer was clearly working. Rex's cock seemed even more sensitive, twitching and leaking pre cum steadily onto her tongue. She swallowed every drop greedily, moaning louder.
"Give mommy more. Leak for me, baby. I want to taste how much you need this."
For nearly twenty minutes she worshipped him. Long, wet, noisy sucks. Deep throating as far as she could without triggering the knot. Sloppy kisses and long licks along the entire length, paying special attention to the swelling base without ever letting it push past her lips. Her own arousal dripped down her thighs onto the rug as she lost herself in the act, one hand slipping between her legs to rub her swollen clit in time with her sucking.
When Rex's thrusting grew frantic and his balls drew up tight, Elena knew he was close. She pulled back just enough to look up at him with lust filled green eyes, lips shiny and swollen.
"Cum for mommy, Rex. Shoot it all in my mouth. Fill your dirty little bitch with that hot dog cum. Don't hold back."
She dove back down, sucking with desperate intensity, tongue working furiously. Rex's entire body tensed. With a deep, guttural growl he erupted.
Thick, powerful jets of cum blasted across her tongue and straight down her throat. The load was heavy and voluminous thanks to the pills, rope after rope flooding her mouth faster than she could swallow. Creamy white seed spilled from the corners of her lips, running down her chin and dripping onto her breasts in sticky strands. Elena moaned loudly around his pulsing cock, swallowing as much as she could while the overflow made a complete mess of her face and chest.
She kept sucking gently through his orgasm, milking every last drop until his spasms finally slowed. Only then did she pull off with a wet pop, strings of cum and saliva connecting her lips to his still twitching shaft.
Elena sat back on her heels, breathing hard, her face and tits glistening with his cum. She licked her lips slowly, savoring the thick, salty taste, then looked up at Rex with a satisfied, wicked smile.
"Good boy. Such a good fucking boy."
She wiped a thick strand of cum from her cheek and sucked it off her finger, eyes half lidded with pleasure.
"Tomorrow we combine the oral enhancer with a low dose of Knotlock 9 again. But tonight… mommy needs to ride that afterglow for a while."
Rex panted happily, tail wagging slowly as he leaned down to lick her cum covered face.
Elena laughed softly, already planning the next experiment in her head.
Experimental Knot – Part 6: Full Breeding
One days later, Dr. Elena Voss could no longer wait.
She had spent the morning finalizing the ultimate combination: a moderate dose of Knotlock 9 mixed with the new Oral Enhancer Alpha and a fresh seminal volume booster. The pills were already crushed and waiting in Rex's bowl. The moment he finished eating, she felt the familiar rush of heat between her legs.
Elena dropped to her hands and knees on the living room rug, completely naked, her full breasts hanging heavily and her ass raised high. Her long blonde hair spilled across the floor like a golden curtain. She looked back over her shoulder, green eyes dark with lust.
"Come here, Rex. Mommy needs you to fuck her properly tonight."
Rex padded over, his sleek black body already showing signs of the pills working. His red cock was sliding out, thick and ready. Elena reached back and guided the tapered tip to her dripping entrance.
"Put it in me, baby. Mount your dirty bitch."
The big Doberman did not need telling twice. He reared up, front paws landing heavily on her back as he thrust forward. His hot, slick cock speared into her soaked pussy in one powerful stroke, stretching her walls wide open with a wet squelch. Elena cried out in pleasure, fingers digging into the rug.
"Fuck yes! That is it, Rex. Shove that big dog cock deep inside mommy. Breed me like the horny slut I am."
Rex began pounding her hard in doggystyle, his hips slamming against her ass with loud, rhythmic slaps. Each thrust drove him deeper, the chemically enhanced shaft dragging along her g spot with every stroke. Elena pushed back to meet him, her voice turning into a steady stream of filthy encouragement.
"Harder, baby. Pound mommy's tight cunt. You love fucking your owner from behind, don't you? Making me your personal breeding bitch. Yes, just like that. Deeper. Stretch me open."
Her full breasts swung wildly beneath her as Rex rutted faster. The knot at the base of his cock was already starting to swell, bumping insistently against her stretched lips with every powerful thrust.
"Feel that fat knot growing for me? It is going to lock inside and fill me up so good. Keep going, good boy. Make mommy cum all over your cock."
Elena came hard within minutes, her walls clamping down around him as she screamed into the rug. Rex did not slow down. He kept hammering into her, growling low in his throat, his heavy balls slapping against her clit.
After several long minutes of relentless doggystyle fucking, Elena's arms gave out. She collapsed forward onto her chest, ass still raised high for him.
"Turn me over, baby. Mommy wants to look at you while you breed me."
Rex pulled out with a wet pop. Elena quickly rolled onto her back and spread her legs wide, pulling her knees toward her shoulders. Rex mounted her again in full missionary position, his front paws on either side of her head. His thick cock sank back into her dripping pussy with ease.
"Yes… fuck me face to face, Rex. Look at mommy while you fill her up."
The angle was even deeper now. Elena stared up at him, eyes glassy with pleasure, as he thrust into her with long, powerful strokes. Her hands roamed over his furry chest and sides, pulling him closer.
"You are so deep inside me, baby. Hitting mommy's womb with every thrust. Such a good breeding dog. Pump all that hot cum into your owner. Make my belly swell with your load."
Rex's knot swelled rapidly, stretching her wider and wider until it finally popped inside with a loud, obscene squelch. The massive bulb locked behind her pubic bone, grinding relentlessly against her g spot. Elena's back arched off the floor as another powerful orgasm ripped through her.
"Fuck, it is so big! You are locking mommy so tight. Don't stop. Keep thrusting while you are stuck inside me. Fill me up, Rex. Breed your filthy little bitch."
The tie lasted over an hour. Rex kept making small, instinctive thrusts even while locked, the huge knot pulsing and throbbing deep inside her. Elena came twice more, her body shaking uncontrollably, dirty talk spilling from her lips the entire time.
When Rex finally reached his peak, the load was enormous. Thick, heavy ropes of hot dog cum blasted directly against her cervix in powerful jets. Her lower belly visibly swelled as he flooded her, the pressure so intense that creamy white seed forced its way out around the massive knot in messy, gushing spurts, soaking the rug beneath them.
Elena trembled beneath him, whispering hoarsely, "Good boy… fill mommy so full… such a perfect breeding dog."
After the knot finally began to soften and Rex pulled free with a wet flood of cum pouring from her stretched pussy, Elena was not done.
She pushed him gently onto his back on the rug and crawled between his hind legs. Her green eyes were glazed with pure depraved lust as she spread his cheeks with both hands.
"Now for mommy's favorite reward," she purred.
Elena leaned in and pressed her tongue flat against Rex's tight, musky asshole. She licked slowly at first, savoring the filthy, animal taste, then grew bolder. Her tongue circled the puckered hole, probing gently, pushing inside as far as she could. She moaned loudly into his ass, the vibration traveling through him as she ate him out with hungry, sloppy strokes.
"You taste so fucking dirty, baby. Mommy loves rimming her good boy's ass after he breeds her. Such a nasty little treat."
She licked and sucked with depraved enthusiasm, tongue fucking his hole while one hand lazily stroked his softening cock. Thick globs of their mixed cum still dripped from her own pussy onto the rug as she worshipped him.
Rex panted happily, tail thumping weakly against the floor while Elena continued her lovely, filthy rimjob, completely lost in the depraved aftercare.
She finally pulled back, lips shiny and swollen, and smiled up at him with a wicked, satisfied grin.
"Next time we go even higher on the dose. For science… and for mommy's greedy holes."