Sentence:  Out of the whole ninety-five [cows] there were eight in particular ... who, though the teats of one or two were as hard as carrots, gave down to her with a readiness that made her work on them a mere touch of the fingers.  Knowing, however, the dairyman's wish, she endeavoured conscientiously to take the animals just as they came, excepting the very hard <WSD>yielders</WSD> which she could not yet manage. 
Meaning of the word marked with <WSD> tags:  Someone or something that yields a crop or other product.