The Farm was an odd place, resting outside the normal bounds of space and time. Here, reality was fragile, moldable, to the point of being dangerous. Nobody knows who created it, or if it was even created at all, and the only one capable of controlling the maleable isolated realm was The Owner. It was a place that not many dared to tread. However, it did promise to pay enough for you to put a dent in your student loans.
Your job was simple; take hourly walks around the property, make sure that none of the animals had escaped, and check for fractures anywhere you could find them. It was a fairly easy job, for the most part.

Today was one of the few days you were told to enter the barn on the far side of the property. The Owner said something about needing to fix the old milking machine for the cows, so you took your tools and wandered out to the rust colored wooden building, and entered its dark maw. 
The air smelled sweet, and although the light from the outside wasn't enough to light to full room, it was enough to see everything you needed to see. Still, it felt strange that a barn wouldn't have a lightswitch close to the main doors.
The job you'd been given was simple, and it was over in about two minutes. There wasn't anything wrong with it, there were just a few bolts that needed tightening. 
Before you were able to leave, the scent in their air hit your nose again; it was still sweet, but moreso than before. It was stronger, too, as though its source was getting closer. You noticed far too late that it had been getting closer with every second you were in the building.
You couldn't see what grabbed you, there wasn't nearly enough light for that, but you could feel it as its slimy skin wrapped itself around both of your ankles, pulling them together, and then out from beneath you. It would've been a painful landing had you not been caught by another 'limb' that lifted you further off of the ground. Before long, it had you bound with your arms strapped to your sides and your legs held tightly together. You couldn't move anything below your head.
"What are you?" Said a voice from the shadows, its feminine voice emerging slowly. You tried to squirm out of its grasp, but none of your movements would even make the bindings around you budge. Whatever this thing was, it was far stronger than you, and it knew it.
You heard it laugh, a sickeningly sweet sound that almost took on the feel of a song. It spoke again.
"Are you the new cow? The Owner did say it would send something my way soon. I had no idea that the new cow would be so yummy-looking, though." You tried to speak, opening your mouth to scream at it, but not a single sound escaped you before that slimy skin slid itself over your mouth, sealing it shut with both superior strength and that slime. It slipped its way into your mouth too, it tasted sweet. "None of that, little morsel. Don't worry, I won't eat you, yet. You still have a lot of milk to produce before I even think of doing such a thing, though I'll admit that it's tempting. You just need to be modified first."
'Modified'. That word sounded bad, but there wasn't any time to think about it. The wet flesh over your mouth seperated itself from your lips for just long enough for you to take a deep breath, and then it pushed itself into you. 
All over your body, you felt more of the slime invade your skin as it somehow began to melt your clothes away. In the span of about two minutes, all of your garments had been replaced by a thick layer of mucus from the limbs that were bound around you. It stuck to the skin, creating a layer of what looked like liquid glass that slowly began to harden and sink into you. Every inch of your skin that it touched began to quickly feel numb, and just as one limb had entered your mouth, more approached your head and backside.
One of them slid straight into your ass while the first of them wriggled around in your mouth, coating your insides with the same material that was growing on your skin, but there was so little resistance that the limbs had free reign to go wherever they wanted. 
Two of them were already inside of you, and then two more slipped their way into your ears. They were tiny enough to not cause any pain, but for a brief moment there was significant discomfort, until you felt them enter the inside of your head. Then, the discomfort was gone.
"There we go," the voice cooed, "no more resisting. Let me take care of you." The voice was inside of your head, as though it was being transmitted directly to your brain, which could've very well been the case. You felt the muscles of your limbs try to move on their own as the tendrils physically interacted with your mind, winding their way around until you could feel them all over your thoughts. The flesh wrapped around you lowered you to the ground, but even when you had been released, your body refused to move on any order you gave it. Your limbs shook and shuddered, even moving at times, but only by the commands being given inside of your head. With those two on your mind, and another tendril stuffed down your throat and up your ass, you were a puppet without strings.
The limbs moved your body around to give the being controlling it easier access, laying you on your back with your head tilted upwards to provide easier access for the tenticle sliding in and out of your throat. 
Another limb attached itself to you, sticking right between your legs and sending shocking stimulation straight into the surrounding area. The sudden burst of pleasure made your body go rigid, but it wasn't even close to done. Again, it sent out a shock that wiped your mind clear for a few seconds. Then it did it again, and again, but each time it did so it seperated from you for a moment only to slap down once again. The area felt heavier each time the tendril moved away, but you couldn't see what was happening. 
Two more of them attached to your chest as well. There was a moment of clarity as you questioned what they were doing there, but as they attached themselves to your nipples, the clarity of replaced by the same thought clearing sensation that was now running back and forth through your body without any sign of stopping. You still couldn't see, but you could feel what was happening to your chest. It was getting heavier, weighing your body down more and more as you felt the skin expand and slide down the sides of your torso.
This went on for a few more minutes, but then again you lost your sense of time every few seconds, so it could've been significantly longer.
When it did let you go, it slid itself out of you all at once; your throat, your ass, your mind, was all free at all the same time. It was jarring, so when you were set back up on your feet the first thing you did was fall forward. That's when you saw everything that had been done to your body.
Between your legs was a cock about as thick as your arm, long enough to reach past your knees, and it was barely visible now past the two massive tits now attached to your chest, the nipples of which were longer than they were wide. You didn't have to look behind you to know that the added weight that had been added to your backside; your ass was much larger than before, and each step you managed to take threatened to send you off balance. Then, you tripped, and fell forward to the floor. You landed on your nipples, which was enough to shatter you. Your mouth shot open to scream, not with pain, but with pleasure, but a very different sound emerged.
"Moooo!" You called out, barely able to register the sound you'd just made. There was still enough panic fogging your mind to make you try to move again, but you simply threw yourself back to the floor instead, resulting in another pleasured bovine scream. The panic was turning pink, and you heard the entity behind you laughing again.
"You turned out so very well." It said, reaching over to grab you by the ankles. It pulled you closer to her, making sure to flick at your nipples as it did so. "You're going to make such nice milk for The Owner, aren't you?" In your dazed state, all you could do was release another moo as the limbs wrapped themselves around your nipples and squeezed hard enough to drag out a small stream of milk. The pleasure was damn near unbearable. "Good cow. Now then, you have work to do." The being carried you over to the old milking machine, and grabbed the pumps that lay scattered on the floor. The three pumps were attached, two to your udders, one to your cock, and the moment they were turned on, milk was forcibly drained from your tits, and your cock was being vigerously stroked by the machine, producing load after load of cum over the next few hours.
With the last bit of mind that was still you, you tried to call out for help. Your moos filled quiet barn, and as your milking continued they became louder and louder as they turned from panic to pleasure. You shot out another load of cum, another stream of milk, and before long you were bucking your hips into the machine and massaging your tits to coax the milk out faster. 
You very quickly lost track of time, but that was ok with you; you were far too busy thinking of all of the milk you'd be able to offer your wonderful Owner, and your graceful mistress, before you were finally emptied and drained completely.
You were going to be such a good cow for The Farm.