Effects of lactation on metabolic and reproductive hormones in Lipizzaner mares.
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.
Heidler
B
B
Clinic for Obstetrics, Gynecology and Andrology, University of Veterinary Sciences, Vienna, Austria.
Parvizi
N
N
Sauerwein
H
H
Bruckmaier
R M
RM
Heintges
U
U
Aurich
J E
JE
Aurich
C
C
D000818:Animals; D005260:Female; D005865:Gestational Age; D013006:Growth Hormone / Q000097:blood; D006728:Hormones / Q000097:blood*; D006736:Horses / Q000502:physiology*; D007334:Insulin-Like Growth Factor I / Q000032:analysis; D007774:Lactation / Q000502:physiology*; D020738:Leptin / Q000097:blood; D007986:Luteinizing Hormone / Q000097:blood; D011247:Pregnancy; D011388:Prolactin / Q000097:blood; D012098:Reproduction
D006728:Hormones; D020738:Leptin; D007334:Insulin-Like Growth Factor I; D011388:Prolactin; D007986:Luteinizing Hormone; D013006:Growth Hormone