Prolactin and progesterone concentrations around farrowing influence sow colostrum yield

In swine, colostrum production is induced by the drop of progesterone concentrations which leads to theprepartum peak of prolactin. Prolactin regulates mammary cell turnover and stimulates lacteal nutrientsynthesis. Progesterone inhibits prolactin secretion and down-regulates the prolactin receptor in the mammarygland. The aim of the study was to determine if the relative peripartal concentrations of progesteroneand prolactin (PRL/P4 ratio) influence sow colostrum production. Twenty-nine Landrace Large Whiteprimiparous 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 bloodsamples were collected during the peripartum period (i.e. from -72 to +24 h related to farrowing) and wereassayed for progesterone and prolactin. Sows were retrospectively categorized according to their PRL/P4ratio 24 h before farrowing: 3 (HighPRL/P4, n=13). Data were analyzed byANOVA using the MIXED procedure (SAS Inst.), except for piglet mortality (GENMOD procedure). Duringthe peripartum period, the circulating concentrations of progesterone were lower (P0.10). Piglet mortality between birth and T24 averaged 10.0% in LowPRL/P4 litters and 7.0% inHighPRL/P4 litters (P=0.29). In conclusion, a higher PRL/P4 ratio 24 h prepartum, characterized by lowerprogesterone concentrations and a trend for higher prolactin concentrations peripartum, led to a greatercolostrum yield