Endocrine changes before and after weaning in response to boar exposure and altered suckling in sows

摘要

Summary. Eighteen sows (6 primiparous and 12 multiparous) were allotted randomly within parity to two lactational treatments: litter separation (LS; 6 h/day) plus boar exposure (BE; 1 h/day; N = 14) beginning 8 days before weaning (4 weeks) and no LS + no BE (controls; N = 4). Blood was collected from all sows via indwelling venous catheters at 20-min intervals for 5 h on Days ?1, 0, 1, 2 and 3 from start of treatment. Control sows and those exposed to LS + BE not exhibiting oestrus during lactation were resampled on Days ?1, 0, 1 and 2 from weaning. All 10 multiparous sows receiving LS + BE exhibited oestrus during lactation, whereas none of the 4 primiparous sows exposed to LS + BE or the 2 control multiparous and 2 control primiparous sows exhibited lactational oestrus. Overall concentrations of LH in serum were higher (P < 0·05) in sows receiving LS + BE than in control sows during lactation, whereas overall FSH was higher (P < 0·05) in primiparous than multiparous sows. Number and amplitude of pulses of LH were greater (P < 0·05) for treated primiparous than multiparous sows during lactation. Oestradiol-17β increased (P < 0·05) in sows during LS + BE and was higher (P < 0·01) in multiparous sows of this group than control multiparous or treated primiparous sows. Preweaning concentrations of cortisol and progesterone in serum were higher (P < 0·05) in treated than control sows for multiparous and primiparous animals.