Steroid profile of porcine follicular fluid and blood serum: Relation with follicular development

The aim of this study was to identify follicular fluid (FF) steroids which reflect follicular development in the early stages of the follicular phase and to establish whether the levels of these FF steroids correspond to their levels in serum. If these relations are established, serum steroid profiles may be used to monitor follicular development already in this early stage of the follicular phase. We used samples of two experiments, one with multiparous sows at the onset of the follicular phase (weaning) and one with primiparous sows at the midfollicular phase (48 hr after weaning). Complete steroid profiles were measured in pooled FF of the 15 largest follicles and serum using high‐performance liquid chromatography‐tandem mass spectrometry. In experiment 1, pooled FF volume, as a measure for average follicle size, tended to be positively related to higher FF 17β‐estradiol levels (β = 0.56, p = .08). In experiment 2, a larger FF volume was related not only to FF higher 17β‐estradiol levels (β = 2.11, p