Effects of lactation on metabolic and reproductive hormones in Lipizzaner mares

• Published in: Domestic animal endocrinology Vol. 25; no. 1; pp. 47 - 59
• Main Authors: Heidler, B., Parvizi, N., Sauerwein, H., Bruckmaier, R.M., Heintges, U., Aurich, J.E., Aurich, C.
• Format: Journal Article
• Language: English
• Published: United States Elsevier Inc 01.07.2003
• Subjects: Animals; Female; foaling; Gestational Age; Growth Hormone - blood; hormone secretion; Hormones - blood; Horse; horse breeds; Horses - physiology; IGF-1; insulin-like growth factor I; Insulin-Like Growth Factor I - analysis; Lactation; Lactation - physiology; Leptin; Leptin - blood; luteinizing hormone; Luteinizing Hormone - blood; mares; postpartum period; Pregnancy; prolactin; Prolactin - blood; Reproduction; somatotropin; temporal variation; IGF-1; Lactation; LH; Leptin; Horse
• ISSN: 0739-7240; 1879-0054
• DOI: 10.1016/S0739-7240(03)00044-4

In this study, growth hormone (GH), insulin-like growth factor 1 (IGF-1), leptin, luteinising hormone (LH) and prolactin were analyzed in mares from late pregnancy throughout lactation (group 1, n=46) and in non-lactating mares (group 2, n=11). Plasma GH concentrations in group 1 mares during gestation and lactation were lower than in mares of group 2 ( P<0.05). Highest IGF-1 levels were found in lactating mares in the week of foaling. IGF-1 concentrations decreased continuously thereafter. Plasma leptin concentrations decreased after foaling and, for 4 weeks, were lower in lactating than in non-lactating mares ( P<0.05). Reduced leptin concentrations may promote feed intake and allow lactating mares to avoid an energy deficit. In group 1 mares, prolactin concentrations reached a maximum in the week of foaling and decreased rapidly thereafter. Plasma LH concentrations in group 1 mares before foaling were lower than at corresponding times in group 2 ( P<0.05). LH concentrations then increased and did no longer differ from group 2 until week 2 postpartum. This increase may contribute to the resumption of cyclic ovarian activity in postpartum mares. Subsequently, LH levels in lactating mares decreased again ( P<0.05). Increased IGF-1 concentrations early postpartum might contribute to ovarian stimulation while reduced IGF-1 and GH concentrations later in lactation might cause reduced stimulation. The changes in somatotrophic hormones could thus explain, at least in part, a more pronounced stimulation of ovarian function early postpartum than during the following months of lactation.