Effect of dosage and duration of altrenogest treatment on 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.