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

Abstract

The aim of this study was to investigate the effect of altrenogest (ALT) treatment on follicular development and ovulation in sows. Sows (parity 6-9; D0: weaning day) were assigned to four treatments as follows: control (no ALT treatment; n = 20), ALT-4-0 (ALT 20 mg/day, 5 days; D-4-D0; n = 20), ALT-4-2 (ALT 20 mg/day, 7 days; D-4-D2; n = 23), and 2ALT-4-2 (ALT 20 mg twice a day [40 mg/day], 7 days; D-4-D2; n = 24). The sows in each group were further divided into three groups based on slaughter periods: day 1 (DF1) and day 4 (DF4) of the follicular phase, and after the initiation of estrus. The number of follicles was reduced on DF4 compared to DF1 (P < 0.001). On DF1, follicular size (FS) of the control was larger than that of ALT-4-0, ALT-4-2, and 2ALT-4-2, but on DF4, FS of ALT-4-2 and 2ALT-4-2 was larger than that of the control and ALT-4-0 (P < 0.001). The coefficient of variation of FS on DF4 was smaller in ALT-4-2 compared to the control and 2ALT-4-2 (P < 0.05). Ovulation rate was similar between groups (P - 0.05). ALT improved follicular growth and the homogeneity of FS without affecting ovulation.