What races can this apply to?
As a variant of a racial feat, looking at which races satisfy the prerequisites is important. Part of the reason Squat Nimbleness need not consider the balance as heavily in providing an additional 5 feet of movement is that the races it applies to have a base movement speed of 25 feet. Here are the races which (can) have hooves:
- Ravnican Races
- The Ravnican Races of Minotaur and Centaur each fit this category.
- The Tiefling
- The Variant Tiefling in the Sword Coast Adventurer's Guide allows for the presentation of cloven hooves.
- The Simic Hybrid (maybe)
- The Simic Hybrid of Ravnica may fit this category as they are fit with animal enhancement, although generally these enhancement are aquatic, reptilian, or amphibious in nature (and all of the mechanical options as racial features fit that general category).
Re (Simic Hybrid): since there is no mention of hooves in reference to the Simic Hybrid race, you will have to ask your GM if this is an animal characteristic that an individual could incorporate (even if it lacks mechanical significance)
Each of these races have a movement speed of 30 feet or higher making the 5 feet of movement increase more powerful than the version that appears in Squat Nimbleness.
Is it balanced?
Instead of comparing to Squat Nimbleness, I think it is better to compare to the Mobile feat. The Mobile feat offers three benefits:
- Your speed increases by 10 feet.
This is obviously more potent than the 5 feet increase of your Beast of Burden feat, but the 5 feet boost is a bit more than half as effective as being able to outspeed all 30 feet movement speed creatures is more relevant than being able to keep up with 40 feet movement speed creatures. I'd call this a slight pro to Mobile over Beast of Burden.
- When you use the Dash action, difficult terrain doesn't cost you extra movement on that turn.
This is a fairly secondary benefit of Mobile that comes up only in a few situations. I'd argue it carries slightly less applicability to the advantage against prone-effects and force-movement-effects that your Beast of Burden offers. Therefore, it is a slight pro to Beast of Burden over Mobile.
- When you make a melee attack against a creature, you don't provoke opportunity attacks from that creature for the rest of the turn, whether you hit or not
This is the most powerful effect of the Mobile feat and it is compared to a trade-off of +1 Strength and proficiency in a (rarely applicable in my experience) skill. The Beast of Burden trade-offs constitute a moderate boon (ability score fixing can be quite useful) while the Mobile feat's third bullet is an exceptional boon. I'd call this a slight pro to Mobile over Beast of Burden.
Overall, we add up the benefits to either feat and arrive at one more slight pro for Mobile than Beast of Burden. This is certainly within the range of power levels that other feats present, so I conclude that your homebrew feat is balanced compared to official options.