競走 (a race) + 馬, read ば.
Common collocations
- 競走馬を育てる: to raise racehorses
- 引退競走馬: a retired racehorse
- 競走馬の血統: a racehorse's bloodline
Watch out
競走 (a race, running against others) and 競争 (competition in general) share a reading. The horse is always 競走馬.