Relationships between colostrum production by primiparous sows and sow physiology around parturition.

Relationships between hormonal and metabolic changes around parturition and colostrum yield and composition were investigated in 16 Landrace x Large White primiparous sows. Blood samples were taken daily from d 105 of pregnancy to d 2 postpartum (with d 0 being the day of parturition). Colostrum samples were taken at the onset of parturition (T0), and then 3, 6, and 24 h later (T3, T6, and T24, respectively). Colostrum yield was calculated from the beginning of parturition until 24 h later by adding colostrum intake of individual piglets, which was estimated from their BW gain. Colostrum yield averaged 3.22 +/- 0.34 kg. Four sows had very low colostrum production (1.10 +/- 0.12 kg; n = 4), whereas the others produced between 2.83 and 4.64 kg of colostrum (3.93 +/- 0.16 kg; n = 12). Compared with the high-colostrum-producing sows, the low-colostrum-producing sows tended (P < 0.1) to have greater plasma concentrations of progesterone during the 20-h prepartum and tended (P < 0.1) to have smaller plasma concentrations of prolactin 40 and 30 h before parturition. Sows with a low colostrum yield had greater plasma concentrations of glucose than sows with a high colostrum yield from d -9 to -2 (P < 0.05). At the onset of parturition, colostrum from low-producing sows had greater percentages (P < 0.01) of DM, lipids, and GE, but less (P < 0.05) lactose, than that from high-producing sows. The Na:K ratio in colostrum during the 6 h postpartum was greater (P < 0.01) in low-producing sows than in high-producing sows, indicating that cellular junctions between epithelial mammary cells were less tightly closed. Concentrations of IgG in colostrum varied greatly between sows and decreased by approximately 80% between T0 and T24. Within high-producing sows, concentrations of IgG in colostrum at T0, T3, and T6 were negatively correlated (P < 0.05) with lactose concentrations in colostrum at the same times and were positively correlated (P < 0.05) with plasma concentrations of IGF-I measured from d -9 to 0. In contrast, no correlation (P > 0.1) was found between IgG concentrations in colostrum at any time and prolactin, estradiol-17beta, progesterone, or cortisol. In conclusion, sows that produced a low yield of colostrum were characterized by a leaky mammary epithelium and reduced synthesis of lactose, related to delayed hormonal changes before parturition.