Published online by Cambridge University Press: 02 September 2010
Administration of exogenous progesterone (0-55 mg/kg live weight) and oestrone (0-275μg/kg live weight) during various discrete intervals between days 4 and 30 of gestation elicited variable results depending upon the time and duration of administration. Administration of the combined steroids early in gestation (days 4 to 20, trial 1; days 4 to 12, trial 2) tended to affect farrowing performance adversely. In general, advantageous effects on farrowing performance occurred when treatment with exogenous progesterone and oestrone was initiated at day 12 or later of gestation.