Control of oestrus in gilts II. Synchronization of oestrus with a progestagen, altrenogest (Regumate): Effect on fertility and litter size

After control of puberty, 525 crossbred gilts were randomly distributed between two groups: a control group (281), and a treated group (244) receiving 20 mg of Regumate daily for 18 days in the food. Ninety-six percent of Regumate-treated gilts were in oestrus between days 4 and 7 after the end of the treatment. After double A.I. with 6 billion spermatozoa, the farrowing rates and the litter sizes were 88.4% and 9.6, respectively, for the Regumate group, and 80.8% and 9.1 for the controls. This progestagen treatment not only allowed a good synchronization of ovulations, but improved the fertility and the litter size simultaneously.