I had so much fun with this game, I spent much more time on it than I planned to. At first I thought it was a neat racing game, then I unlocked all the buildings and found out the game had much more to it than I expected. The whole body part building aspect is a really cool concept, and juggling between what to spend money on, to make sure you have enough money for mother, race entry fee and to buy parts/new horses was fun to manage. Especially with mother's unpredictable needs it felt like I was always kept on my toes.
In the end I made it all the way to day 19 with 7$ to my name, so I knew I couldn't make it to 20, only being able to enter an intermediate race, but I'm happy with how far I made it. I may try again another time to beat it, but I have other horse games to play for now.
As for suggestions for improvement, aside from the obvious like sound, something small but helpful would be some sort of green plus/red minus indicator for each stat when swapping parts to show which are increasing or decreasing, as there are quite a lot of stats so it takes a while to check and compare.
Also, maybe I just got lucky, but whenever mother ate one of my horses she always picked the one at the bottom of my list, which after I figured it out it made the threat not as scary as all I had to do was buy a random new horse and that made the cost equivalent to her food costs being whatever cost that new horse was instead of the cost being me losing one of my horses, if that makes sense. That being said, if it had been a truly random pick that would really increase the game's difficulty as I mainly focused on upgrading one particular horse and if I lost him then I would've been done for. At the same time though I'm also not sure how players would feel having random chance deciding the fate of their run. I suppose it would incentivise having a roster of multiple good horses. I'm not sure if it's something that even needs to be changed, but it's something to think about.