O atraso do parto utilizando dispositivos intravaginais impregnados com progestágeno não afeta a proporção de leitões nascidos vivos

The objective of this study was to evaluate the efficiency of progestagen intravaginal devices (IVDs) in preventing parturition in sows by determining the effect of delaying parturition on the alive/total born piglets ratio. Evaluations of IVDs containing 0.5, 1.0 or 1.5g progesterone (P4) showed they were not effective in delaying parturition at any dosage tested. In a second experiment, seventy-five sows at day 112 of pregnancy were equally distributed (n=15 per group) in the following treatments: prostaglandin (PGF2 alpha; 250 mu g sodium cloprostenol; control group) or PGF2 alpha and simultaneous insertion of an IVD containing medroxyprogesterone acetate (MPA) for 48h. Control sows initiated labor 27.7 +/- 1.6h after PGF2 alpha injection. The mean time (+/- SEM) between PGF2 alpha administration and parturition was 72.1 +/- 8.8h, 72.7 +/- 3.8h, 82.7 +/- 7.1h and 81.8 +/- 3.5h for MPA 100, 200, 400 and 800mg, respectively, differing from control group (P<0.05). To evaluate the effect of delaying parturition on the alive/total born piglets ratio at birth, sows between days 109 and 112 of gestation received IVDs containing 800mg MPA (on Thursdays) for 72h to prevent parturition in weekends and then were treated with PGF2 alpha at the time of device withdrawal (on Sundays). The alive/total born piglets ratio was 89.0 +/- 1.6, 90.1 +/- 1.2 and 89.0 +/- 1.5% for control (Normal group; n=57 sows), PGF2 alpha-induced (Induced group; n=57 sows), and IVD+PGF2 alpha-induced (MPA800 group, n=56 sows) groups, respectively (P>0.05). These findings confirm that IVDs impregnated with MPA can effectively prevent parturition in sows without affecting the alive/total born piglets ratio and therefore represent an alternative to avoid weekend farrowing in swine herds.