If you talk about young blood, you mean new, young people who are brought into an organization to introduce new ideas and energy. The family business was badly in need of young blood. The selectors have gone for some young blood, fielding a side whose average age is just 26. Note: You can also talk about young bloods, meaning the young people in an organisation or doing a particular activity. Floyd proved he can still compete with the young bloods by becoming the oldest winner of the US Open at 43. Compare with new blood.