Days, weeks, possibly even months passed. Maria had no idea anymore. Occasionally the scientists visited her to take her elsewhere for tests, and sometimes fuck her too.
Everyday was basically the same. Most of the time she was horny, but the alpha usually saw to that at least once a day. By this point though she'd had all the males inside her at least once, today was one of those days. Maria was underneath one of them, back legs stood upright, but bent over so she was holding onto the males front legs for support as it humped back and forth, thrusting itself into her. This quickly became her go to position after arriving. It was hard work supporting them when they tried to mount her normally against the fence, this way was just easier for everyone involved. Even all the males knew it, she was easily the most 'popular' female in the field.
Maria whinnied loudly as she came, the male filling her with his cum at the same time. She laid on the floor, satiated for now, but she knew she'd be ready for more later. Maria snoozed for a few hours, waking up to the familiar deep hunger in her stomach. She'd been hungrier than normal for a number of days now, each day eating more than the previous. She ran her hands over her belly, as large and as round as it was now, she felt a tinge of excitement for it getting bigger. Even her old human breasts had expanded out again, almost as big as they used to be, as if her hormones just weren't sure where to disperse themselves throughout her body.
Maria felt the being inside her shift around. She knew she wasn't the same as the other horses, and sometimes wondered how her child would look too. Would it be like her? Or the others? Or like the men that checked on her? She got to her feet and trotted towards the rest of the horses, gathered around the food. They moved out of the way as she approached, leaving her room to get on her knees and lean into the trough. She ate continuously for 15 minutes, then got up and moved to the beds for another nap. This was generally how her days usually went. Lots of napping, but the pregnancy was making her more tired than normal.
Second nap of the day was usually followed by a session with the alpha, as she awoke to him nudging her with his head, prodding her behind with the tip of his cock. He was already stood over her, she just had to shift into position.
If she wasn't already already awake, she was now.