The primary theme in Herriot's All Creatures Great and Small is that of survival in life's harsh conditions. The setting is the Dales that are tucked in at the feet of the fells that rise high above the Dales. The setting is a metaphor for and a symbol of the hard lives the farmers live in the Dales. They daily experience the cycle of life and death and of illness and struggle, which regularly phases into death. The people of the Dales are desperate to keep their animals alive even when stricken with disease, yet they don't trust the vets who might be the best able to help their animals, which adds to the struggles.
The farmer, Mr Dinsdale, was a long, sad, silent man of few words who always seemed to be expecting the worst to happen. He had a long, sad, silent son with him and the two of them had watched my efforts [with the calving] with deepening gloom.
Sophisticated people living in cities who read Herriot's books found (and find) in them a return to the struggles that the comfort and abundance of city life stand in stark contrast to life in the Dales. Even though separated from the struggle with the land and life, readers nonetheless felt (and feel) a sympathetic pull to the essential nature of a life pitting human against nature. As a consequence, this theme of life's hardships has a universal appeal and makes Herriot's vets universal characters who help to live out the theme with the farmers in the Dales.
No, there wasn't a word in the books about ... the slow numbing if the arms, the creeping paralysis of the muscles as the fingers tried to work ... no mention anywhere of the gradual exhaustion, the feeling of futility ....