Follicle size and reproductive hormone profiles during a post-weaning altrenogest treatment in primiparous sows

Abstract

This study investigated the endocrine background of follicle size changes during post-weaning altrenogest treatment. altrenogest-treated sows received a 20-mg dosage daily at 8.00 a.m. from Day -1 to Day 14 after weaning. On Day -1, only 3/13 altrenogest-treated sows showed LH pulses compared with 8/8 control sows (P=0.001). On Day 0, control sows showed a typical high frequency-low amplitude LH pattern, indicative for recruitment of oestrogenic follicles. In altrenogest-treated animals on Day 0, half of the sows showed high frequency-high amplitude pulses from 4-5h after weaning. In altrenogest-treated sows, average follicle size increased from 3.1±0.5 mm on Day 0 to 4.4±0.6mm on Day 5, then decreased to 3.7±0.5 mm on Day 7 and stabilised thereafter. FSH and oestradiol (E2) concentrations showed a distinct diurnal pattern; high at 7.00 a.m. and low at 3.00 p.m. E2 concentrations (7.00 a.m.) showed a 2.5-fold increase from Day -1 to Day 2, and subsequently a 2-fold decline to reach a plateau at Day 8. FSH concentrations reached maximum levels by Day 5 and slowly declined afterwards. In conclusion, once-daily administration of altrenogest starting one day before weaning delays the weaning-induced increase in LH pulses. Although FSH and follicle size increase until Day 5 after weaning, follicle E2 production already decreased from Day 2 after weaning. Post-weaning altrenogest treatment thus results in a follicular wave of follicles that lose oestrogenic competence at Day 2 after weaning, presumably related to the changed LH dynamics during altrenogest treatment.

Influence of Backfat Thickness and the Interval from Altrenogest Withdrawal to Estrus on Reproductive Performance of Gilts

“…The altrenogest provides an artificial luteal phase via suppression of gonadotro-phins, particularly LH, and following the withdrawal of altrenogest from primiparous sows the LH pulsatility recovers after several hours, the timing depending on the duration of feeding. With recovery of LH pulsatility the follicular phase is initiated, and most gilts will exhibit estrus 4 to 6 days later [ 6 ]. This variability in the interval to the start of follicular phase, and the innate variability in duration of the follicular phase, results in variation of the interval between last feeding of altrenogest and onset of estrus.…”

Altrenogest treatment effects on the reproductive performance of sows during transition to batch farrowing

“…Therefore, in the ALT7 group, treatment resulted in a reduction of approximately 10% of piglets produced in relation to the other groups. Previous studies evaluated ALT supplementation in primiparous sows to induce a longer WEI, allowing the recovery of body reserves lost during lactation (VAn LEEUWEn et al, 2010;VAn LEEUWEn et al, 2011;WERLAnG et al, 2011;VAn LEEUWEn et al, 2015). However, in this study, ALT supplementation aimed to synchronize the estrus and insemination of weaned primiparous and pluriparous sows during the transition period for a batch farrowing system of 21 days.…”

“…Altrenogest (ALT) is the only product commercially available for controlling estrus and ovulation in swine females. It inhibits GnRH release and, consequently, inhibits LH release (VAn LEEUWEn et al, 2015). The ALT treatment must start before the increase of LH pulse frequency, i.e.…”

Altrenogest treatment before weaning improves litter size in sows

“…Hormonal control of ovary functionality is widely used by swine industry (De Rensis & Kirkwood, ). Altrenogest, a synthetic progestin, inhibits follicular development, and therefore, it is mostly used to group oestrus, mainly in gilts and primiparous sows (Kraeling & Webel, ; van Leeuwen et al., ), in which it also improves reproductive performance (Boyer & Almond, ; van Leeuwen et al., ). The aim of this study was to evaluate whether a short‐term treatment of altrenogest during the last days of lactation could regulate the follicular waves at weaning and thus improve the reproductive performance of weaned sows, in both favourable and unfavourable seasons.…”