Variation in LH pulsatility during 24h after a postweaning altrenogest treatment in relation to follicle development in primiparous sows

Split‐weaning Before Altrenogest Synchronization of Multiparous Sows Alters Follicular Development and Reduces Embryo Survival

“…This seems to be substantiated with the finding that at Day 3 after weaning, split‐weaned sows with low embryo survival had fewer medium‐sized follicles (3–5 mm) and higher numbers of larger sized follicles in their follicle pool. These results are in accordance with findings from a previous study (van Leeuwen et al. 2011a,b), in which reduced farrowing rates after a 4–8‐day post‐weaning altrenogest feeding period were found by possible ageing of the larger follicles during altrenogest feeding, which could have reduced fertility.…”

“…This study used SW to stimulate follicle development before weaning and study effects on subsequent reproductive performance after post‐weaning altrenogest feeding, as previous study showed that a sow’s response to post‐weaning altrenogest feeding is influenced by follicle size at weaning (van Leeuwen et al. 2011a,b).…”

“…2008; van Leeuwen et al. 2010) or on follicular size at the initiation of altrenogest feeding (van Leeuwen et al. 2011a,b).…”

“…2011a,b). For example, sows with large follicles at weaning had decreased farrowing rates after an 8 days post‐weaning altrenogest feeding (van Leeuwen et al. 2011a,b), perhaps because of ‘ageing’ of the larger follicles during altrenogest feeding.…”

Effect of dosage and duration of altrenogest treatmenton follicular development and ovulation in sows*

“…However, a different aspect was found, which was that ALT treatment at 20 mg/day for 7 days did not obstruct follicular development to a large size completely, so large follicles on DF1 in ALT-4-2 were present. Administration of ALT at 20 mg/day allowed further growth of follicles because the period of 12 h after ALT treatment had more variability of LH pulse and concentration that could permit follicular development (28). Meanwhile, ALT treatment at 40 mg/day (20 mg twice a day, 12-h interval; 2ALT-4-2) could inhibit or delay follicular growth completely.…”