Menstruation Research Today is a free monthly online journal that collates and summarizes the latest research about Menstruation, including details on menstrual cycle, pregnancy, pain, irregular menstruation.

Follicle development during luteal phase and altrenogest treatment in pigs.

Soede NM, Bouwman EG, Langendijk P, van der Laan I, Kanora A, Kemp B

Animal Sciences Group of Wageningen University, Department of Animal Sciences, Wageningen, The Netherlands. nicoline.soede@wur.nl

Synchronization of the oestrous cycle of gilts using altrenogest treatment has been found to increase ovulation rate. The current experiment investigated if the increase in ovulation rate after altrenogest treatment is related to increased follicle size at the end of altrenogest treatment compared with late luteal phase follicles. Crossbred gilts (n = 15) received altrenogest during 18 days [20 mg Regumate (Janssen Animal Health, Beerse, Belgium)], starting 5-7 days after onset of first oestrus. Control gilts (n = 15) did not receive altrenogest. At days 10-12 of the oestrous cycle [i.e. in the presence of corpora lutea (CL)], average follicle development was 2.51 +/- 0.20 mm (assessed with ultrasound) in altrenogest-treated gilts and 2.58 +/- 0.16 mm in control gilts (p > 0.10). During the last days of altrenogest treatment (i.e. when CL had gone into regression), average follicle size had increased to 3.01 +/- 0.31 mm (p < 0.05). Subsequent ovulation rate was 16.6 +/- 1.7 in altrenogest treated gilts and 15.1 +/- 1.2 in control gilts (p < 0.05). Altrenogest treatment resulted in increased follicle size after regression of the CL, showing that suppression of follicle growth by altrenogest alone is less severe than suppression by endogenous progesterone (either with or without altrenogest). Altrenogest treatment also resulted in a higher ovulation rate. However, it is unclear if the increased follicle size and higher ovulation rate after altrenogest treatment are causally related, as the relation between the two on an animal level was not significant.

Published 17 May 2007 in Reprod Domest Anim, 42(3): 329-32.
Full-text of this article is available online (may require subscription).

© 2004-2008 Menstruation Research Today. All Rights Reserved.