What is the main conflict in All Things Bright and Beautiful by James Herriot?

The novel "All Things Bright and Beautiful" details the life and work of country veterinarian James Herriot during the early years of his practice. Herriot writes his touching stories, which feature the antics of the animals he treats as well as their owners' eccentricities, from his own experience as an animal doctor in Yorkshire, England. Through his stories Herriot shares the challenges of his job as well as the fulfillment and joy he gains working with the animals.