Progesterone and Corticosteroids in the Initiation of Lactation in the Sow

Abstract

The concentration of lactose in the mammary secretion from individual glands of two sows increased significantly (P < 0·01) between 0 and 24 h after parturition. In six sows studied during the perinatal period there was a negative correlation (r = -0 .80; P < 0·02) at parturition between the concentration of progesterone in the blood and the concentration of lactose in the mammary secretion. Furthermore, the increase in concentration of lactose in the mammary secretion after parturition was related to the timing of the decline of plasma progesterone to low levels. The results indicate that the initiation of lactation occurs within 24 h of parturition in most sows, and the results are consistent with the hypothesis that progesterone withdrawal acts as the 'trigger'. Neither the changes in corticosteroid binding globulin nor the changes in total corticosteroids were temporally related to the initiation of lactation. However, a circadian rhythm was observed for total corticosteroids in the blood of three out of nine lactating and pregnant sows, whereas no circadian rhythm was observed in progesterone of the four pregnant sows. The results are discussed in relation to the disease complex mastitis-metritis-agalactia.

Hormones, IgG and lactose changes around parturition in plasma, and colostrum or saliva of multiparous sows

“…The increase in concentrations of lactose in the colostrum occurred under low P4 plasma concentrations but high E2 and PRL concentrations. This was in agreement with the suggested inhibitory action of P4 [4,47,48] and stimulatory actions of E2 and PRL [34,35,49] on lactose synthesis in the mammary glands. The decrease in the ratio of lactose concentrations in colostrum over those in plasma before and during parturition is in accordance with the passage of lactose from the colostrum to the blood circulation.…”

“…Despite a decrease following parturition, our data confirm that plasma PRL concentrations remain relatively high thereafter, which is likely due to stimulation by the suckling piglets [36,37]. The existence of a negative correlation between P4 and E2 and, between P4 and PRL, together with the coincidental fall of P4 on the one hand and rises in E2 and PRL on the other hand, support the proposed role of the P4 decrease as the trigger for other hormonal variations at parturition [3,4,35,38].…”

“…This elevated salivary to plasma cortisol ratio around parturition can be explained by a lower binding of cortisol to blood proteins at that time. Indeed, plasmatic concentrations of CBG do not vary around parturition [4], while cortisol concentrations show a 4-fold increase during farrowing. The binding capacity of CBG for cortisol is therefore likely exceeded [69] and the free cortisol fraction increases up to 28% of the whole fraction around parturition instead of 10-13% during gestation [69,70].…”

“…3 Correlation between concentrations in plasma and lactoserum. 4 Correlations for each period were not calculated since the ratio of concentrations in lactoserum or saliva over those in plasma did not vary significantly with time. 5 Correlation between concentrations in plasma and saliva.…”

“…The roles of hormones such as progesterone (P4), oestradiol-17β (E2), cortisol and prolactin (PRL) on the initiation of lactation and colostrum production have been demonstrated [1,2]. The withdrawal of P4 before parturition acts as a trigger for a succession of hormonal changes leading to farrowing and to colostrum and milk production [3][4][5]. This fall in P4 allows PRL secretion to increase while E2 and cortisol amplify the 382 N. Devillers et al stimulatory action of PRL on the mammary glands [2].…”