Thurs Nedarim 81

The Gemara says that if he she swears off working for their parents or to give straw to his cattle, he cannot be Meifer, since she is not obligated to do this for him However, he may Meifer if she swears off pouring him wine, wash him or spread his sheets on his bed, since she's obligated to him.

Ran asks: however, the Gemara in Kesuvos said she's also obligated to feed his cattle, so why can't he be Meifer?

Ran answers: we refer to after he hired four maids, which they do all of the wife's duties, so she's no longer obligated to do so. However, this exemption only applies to work. However, poring wine etc she's still obligated, because this is not regular work, but actions to create closeness between wife and husband.