У лошади болит копыто.

The horse's hoof hurts.

Breakdown of У лошади болит копыто.

• болеть: to hurt
• лошадь: the horse
• копыто: the hoof

Questions & Answers about У лошади болит копыто.

Why does Russian say у лошади instead of just using лошадь as the subject?

Because Russian often uses the pattern у + genitive + болит/болят + body part for aches and pains.

So the structure is:

• у лошади = of the horse / by the horse
• болит копыто = the hoof hurts

Literally, it is something like At the horse, a hoof hurts, but natural English is The horse's hoof hurts or The horse has a sore hoof.

This is a very common Russian pattern:

• У меня болит голова = My head hurts
• У собаки болит лапа = The dog's paw hurts

Why is it лошади and not лошадь?

After the preposition у, Russian uses the genitive case.
The noun лошадь changes to лошади in the genitive singular.

So:

• dictionary form: лошадь
• after у: у лошади

This is just normal case change, not a special idiom limited to this sentence.

Could лошади here mean horses?