Differences in reproductive performance, embryo development, interferon-tau secretion by the conceptus and luteal function in ewe lambs synchronized in oestrus before or after the spontaneous onset of luteal activity preceding puberty.
In mid-September, 1 month before the insertion of intravaginal pessaries to induce sexual activity, blood samples were collected every 4 days from 16 ewe lambs aged 7 months, in order to determine the incidence of ovulations by measurement of plasma progesterone concentrations. It has been studied whether the response to a progestagen treatment of ewe lambs apparently close to puberty could be modified by the onset of the ovarian events preceding puberty. The effect of the presence or absence of ovulations prior to progestagen treatment on the potential reproductive performance (fertility, litter size and fecundity), embryo development [embryo quality and interferon-tau (IFNtau) secretion], luteal function (progesterone secretion in vitro) and endometrial progesterone content was studied in seven ovulating (Ov+) and nine nonovulating ewe lambs (Ov-) on day 14 after mating. The best potential reproductive results were obtained with Ov+ animals, although these differences could not be initially attributed to either different progesterone secretion in vitro or concentration of endometrial progesterone. Irrespective of the experimental groups, secretion of progesterone by luteal tissue from ewe lambs with normal embryos was significantly greater (p<0.05) than that of animals with abnormal embryos or with no embryos. Normal embryos secreted a higher amount of IFN-tau than those embryos classified as abnormal (p<0.07). In conclusion, ewe lambs which exhibit luteal activity before puberty have the highest levels of reproductive performances after a progestagen treatment. Corpora lutea from ewe lambs with normal embryos had higher rates of progesterone secretion in vitro and their embryos had a higher IFN-tau production by the embryos, indicating greater capacity for subsequent development.
Abecia
J A
JA
University of Zaragoza, Department of Animal Production and Food Science, Faculty of Veterinary, Zaragoza, Spain. alf@posta.unizar.es
Forcada
F
F
Zúñiga
O
O
D000818:Animals; D003338:Corpus Luteum / Q000378:metabolism / Q000502:physiology*; D005314:Embryonic and Fetal Development / Q000502:physiology*; D004717:Endometrium / Q000737:chemistry; D004973:Estrus Synchronization; D005260:Female; D007370:Interferon Type I / Q000096:biosynthesis*; D011247:Pregnancy; D011257:Pregnancy Proteins / Q000096:biosynthesis*; D011374:Progesterone / Q000032:analysis / Q000097:blood; D012098:Reproduction / Q000502:physiology*; D012756:Sheep / Q000196:embryology / Q000502:physiology*
D007370:Interferon Type I; D011257:Pregnancy Proteins; C020947:interferon tau; D011374:Progesterone