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International audience; Like most farm animals, the piglet is born devoid of systemic humoral immunity and therefore relies on maternal immunoglobulins G (IgG) provided by colostrum. Concentrations of IgG in colostrum are highly variable among sows and factors influencing them are not fully known in pigs. Although passive diffusion between mammary epithelial cells cannot be excluded, the uptake of IgG by mammary glands in pigs could be mediated by a Fc-specific receptor, the neonatal Fc receptor (FcRn), as is the case in ruminants. In cattle, the expression of FcRn could be stimulated by the decrease in progesterone/oestradiol ratio in late pregnancy and then be inhibited by the peripartum peak of prolactin. The aim of the present study was to investigate the relations between hormonal concentrations around parturition and colostral IgG concentrations in primiparous sows. Colostrum samples were collected in 40 Landrace × Large White primiparous sows at the onset of parturition (t0) and 24 h later (t24) and were assayed for IgG concentrations. Colostrum yield was estimated during 24 h starting at the onset of farrowing using piglets’ weight gains. Jugular blood samples were taken on d-8, d-2, d-1 and the day of farrowing (d0) and were assayed for prolactin, progesterone, oestradiol-17β, cortisol, IGF-I, and IgG. Amounts of IgG exported into colostrum in 24 h were estimated (colostrum yield x ([IgG] at t0 + [IgG] at t24)/2). Analyses of correlations and multiple regression were performed. Multiple regression was focussed on a subset of 20 sows because one of the most contributing variables (IgG concentrations in sow plasma) had been measured in 20 sows only. Concentrations of IgG in colostrum (means ± SD) averaged 70.5 ± 23.5 and 13.0 ± 7.4 mg/mL at t0 and t24, respectively. Concentrations of IgG in colostrum at t0 were positively correlated with plasma concentrations of IgG at all times (with IgG on d-1: r = 0.61, P = 0.004) and IGF-I on d0 (r = 0.33, P = 0.041) and were negatively correlated with prolactin on d-2 (r = -0.36, P = 0.031). In the multiple regression analysis, variation in colostral IgG concentrations at t0 were explained by plasma concentrations of IgG on d-1 (36%, P = 0.005), prolactin on d-2 (24%, P = 0.019), and progesterone on d-8 (6%, P = 0.118). Amounts of IgG exported in 24 h averaged 157 ± 55 g and this value was partly explained by plasma concentrations of IgG on d-1 (37%, P = 0.004) and progesterone on d-8 (13%, P = 0.044). In conclusion, IgG concentrations in colostrum at the onset of farrowing are related to IgG concentrations in sow plasma in late pregnancy, as previously reported, and IgG transfer into colostrum could be partly regulated by circulating progesterone in sows.

International audience; Hormonal changes involved in the farrowing process partly control the initiation of lactation. Inducing farrowing by injection of prostaglandins may alter the normal prepartum hormonal “cascade.” The aim of the study was to investigate the consequences of farrowing induction on colostrum yield and composition, as well as newborn piglet growth. Gilts were treated with 2 mg of alfaprostol on d 113 of gestation (induced farrowing, IF, n = 9) or were injected with 1 mL of a saline solution (natural farrowing, NF, n = 11). Colostrum production was estimated during 24 h, starting at the onset of parturition, based on piglet weight gains. Colostrum samples were collected during the 36 h following the onset of parturition. Blood samples were collected from sows as of d 112 of pregnancy until d 2 postpartum (d 0 being the day of parturition). Piglet blood samples were obtained at birth, on d 1, and on d 21. Litter size and litter weight at birth did not differ between groups (P > 0.10). Farrowing induction did not influence (P > 0.10) colostrum yield (3.96 ± 0.20 kg) or piglet weight gain during d 1 postpartum (116 ± 8 g). At the onset of farrowing (T0), lactose content in colostrum was greater in IF sows than in NF sows (P < 0.05), whereas colostrum ash and protein contents were lesser (P < 0.05) in IF sows. Concentrations of IgG in colostrum were similar in both groups of sows, while concentrations of IgA at T0 were lower in IF than in NF sows (P < 0.01). Overall, endocrine changes in blood from d -2 until d 2 (cortisol, prolactin, progesterone, and estradiol-17β) were not altered by farrowing induction (P > 0.10), but 1 h after the injection of alfaprostol, IF sows had greater circulating concentrations of prolactin (P < 0.01) and cortisol (P < 0.10) than NF sows. The greater concentration of lactose in colostrum from IF sows could be attributed to this transient increase in prolactin and cortisol. At birth, concentrations of white blood cells were less in piglets born from IF sows (P < 0.01). On d 1 and d 21, piglets from IF sows had similar IgG concentrations in plasma to piglets from NF sows (P > 0.1). In conclusion, farrowing induction at 113 d of pregnancy induced transient hormonal changes in sows and alterations in colostrum composition, without significantly affecting colostrum yield. It also modified some hematological variables of piglets at birth.

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International audience; 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-17 beta, 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.

International audience; The decrease in circulating concentrations of progesterone is the lactogenic trigger in many species. The aim of the present study was to determine the effect of an orally active progestogen, altrenogest, administered in late gestation, on lactogenesis in sows. Gilts were treated with altrenogest (20 mg/d) from d 109 to 112 of gestation (ALT112, n = 6) or d 113 (ALT113, n = 8) or were not treated (control, n = 9). Colostrum production, estimated from the BW gains of the piglets, was measured during 24 h starting at the onset of parturition. Colostrum samples were collected at the onset of parturition until 48 h later. Jugular blood samples were taken from d 8 prepartum until d 3 postpartum. Altrenogest treatment extended the gestation length of ALT113 sows in comparison with control sows (116.3 vs. 114.7 d; P < 0.05). Litter size and litter weight at birth did not differ between groups (P > 0.1). Estimated colostrum yield was not reduced in altrenogest-treated sows compared with control sows (4.20 kg) and tended to be greater in ALT112 (4.73 kg) than in ALT113 sows (3.74 kg; P = 0.09). Altrenogest reduced endogenous progesterone concentrations during the 2 d prepartum in ALT113 relative to control sows (P < 0.05), likely because luteolysis occurred earlier in relation to parturition in ALT113 sows. Altrenogest reduced estradiol-17 beta concentrations during the 2 d prepartum in ALT113 (P < 0.05) and ALT112 (P < 0.1) sows. Altrenogest treatment did not influence the timing of the prepartum peak of prolactin in relation to parturition. The ALT113 sows had lesser (P < 0.05) concentrations of lactose in plasma and a lesser Na:K ratio in colostrum after parturition than Control and ALT112 sows, indicating that the junctions between their mammary epithelial cells were tighter. Concentrations of colostral IgG in sows that received altrenogest tended to be less than in control sows (P = 0.08). In conclusion, altrenogest administered from d 109 to 112 or 113 of pregnancy did not affect lactogenesis in sows, possibly because the treatment delayed farrowing and main hormonal changes without affecting the relative chronology of these changes.

Diplôme : Dr. Ing.

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