Plasma profile of follicle‐stimulating hormone and sex steroid hormones after a single epidural administration of follicle‐stimulating hormone via caudal vertebrae in Holstein dry cows

<jats:title>Abstract</jats:title><jats:p>The conventional follicle‐stimulating hormone (FSH) treatment for bovine superstimulation involves multiple intramuscular injections, which is stressful for animals and onerous. We herein investigated whether a single epidural injection of porcine FSH (pFSH) can induce superovulation and peripheral concentrations of pFSH and steroid hormones after the treatment in Holstein dry cows. We intramuscularly administered pFSH twice daily to three cows for 3 days (control) or a single epidural pFSH administration (epidural). Numbers of follicles (≥10 mm in diameter) at estrus and corpora lutea at luteal phase were counted by ultrasonography. Blood was sampled from 0 to 104 h after the first pFSH administration and plasma pFSH, progesterone, androstenedione, testosterone, and estradiol‐17β concentrations were measured. Numbers of follicles (control: 18.3 ± 7.5, epidural: 15.7 ± 4.0; mean ± SD) and corpora lutea (control: 7.3 ± 4.2, epidural: 8.0 ± 2.6) were similar between both treatments. Plasma pFSH concentrations were higher in epidural than in control (<jats:italic>p</jats:italic> < 0.01). Although no significant differences were observed in progesterone, androstenedione, or estradiol‐17β concentrations between the groups, testosterone concentrations were slightly lower with the epidural treatment than with the control treatment (<jats:italic>p</jats:italic> = 0.08). In conclusion, superovulation was induced by a single epidural injection of pFSH, which achieved higher pFSH level than the multiple injections in Holstein dry cows.</jats:p>