Final answer:
Angus and Hereford breeds of cattle have bulls that tend to have lower weight calves and therefore calving ease.
Step-by-step explanation:
Two breeds of cattle in which the bulls tend to have a lower weight calves and therefore calving ease are the Angus and Hereford breeds. Angus bulls are known for their ability to sire small, easy-calving calves, while Hereford bulls also have a reputation for producing calves with low birth weights and minimal calving difficulties.
For example, Angus cattle have been selectively bred for calving ease for many years. Their smaller size and shorter gestation period contribute to the lower average birth weights of their calves. Similarly, Hereford cattle have been bred for generations to produce lighter calves, making them popular for crossbreeding with other breeds to improve calving ease.