In swine, colostrum production is induced by the drop of progesterone concentrations which leads to the prepartum peak of prolactin. Prolactin regulates mammary cell turnover and stimulates lacteal nutrient synthesis. Progesterone inhibits prolactin secretion and down-regulates the prolactin receptor in the mammary gland. The aim of the study was to determine if the relative peripartal concentrations of progesterone and prolactin (PRL/P4 ratio) influence sow colostrum production. Twenty-nine Landrace Large White primiparous sows were used. Colostrum yield was estimated during 24 h starting at the onset of parturition (T0) using litter weight gains. Colostrum was collected at T0 and 24 h later (T24). Repeated jugular blood samples were collected during the peripartum period (i.e. from -72 to +24 h related to farrowing) and were assayed for progesterone and prolactin. Sows were retrospectively categorized according to their PRL/P4 ratio 24 h before farrowing: <2 (LowPRL/P4, n=16) or >3 (HighPRL/P4, n=13). Data were analyzed by ANOVA using the MIXED procedure (SAS Inst.), except for piglet mortality (GENMOD procedure). During the peripartum period, the circulating concentrations of progesterone were lower (P<0.05) while those of prolactin tended to be greater (P<0.10) in HighPRL/P4 compared with LowPRL/P4 sows. Colostrum yield was greater in HighPRL/P4 compared with LowPRL/P4 sows (4.1 versus 3.5 kg [RMSE=0.7], P<0.05). Colostrum gross composition and IgG and IgA concentrations did not differ between the two groups of sows (P>0.10). Piglet mortality between birth and T24 averaged 10.0% in LowPRL/P4 litters and 7.0% in HighPRL/P4 litters (P=0.29). In conclusion, a higher PRL/P4 ratio 24 h prepartum, characterized by lower progesterone concentrations and a trend for higher prolactin concentrations peripartum, led to a greater colostrum yield.