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Titolo:
INTER-BREED VARIATION IN THE POSTPARTUM EWE RESPONSE TO CONTINUOUS LOW-DOSE INFUSION OF GNRH
Autore:
FRAY MD; LAMMING GE; HARESIGN W;
Indirizzi:
UNIV NOTTINGHAM,AFRC,RES GRP HORMONES & FARM ANIM REPROD SUTTON LE12 5RD LEICS ENGLAND
Titolo Testata:
Theriogenology
fascicolo: 5, volume: 45, anno: 1996,
pagine: 1047 - 1064
SICI:
0093-691X(1996)45:5<1047:IVITPE>2.0.ZU;2-Y
Fonte:
ISI
Lingua:
ENG
Soggetto:
SEASONALLY ANESTROUS EWES; POST-PARTUM EWES; CORPORA-LUTEA; PROGESTERONE PRETREATMENT; PREOVULATORY FOLLICLES; MULTIPLE INJECTIONS; BEEF-COWS; INDUCTION; OVULATION; RH;
Keywords:
EWE; GNRH; INFUSION; POST PARTUM; OVULATION;
Tipo documento:
Article
Natura:
Periodico
Settore Disciplinare:
Science Citation Index Expanded
Citazioni:
33
Recensione:
Indirizzi per estratti:
Citazione:
M.D. Fray et al., "INTER-BREED VARIATION IN THE POSTPARTUM EWE RESPONSE TO CONTINUOUS LOW-DOSE INFUSION OF GNRH", Theriogenology, 45(5), 1996, pp. 1047-1064

Abstract

During the nonbreeding season the pituitary and ovarian responses to a subcutaneous GnRH infusion were investigated in acyclic, lactating Mule ewes which exhibit a deep seasonal anestrus and in Finn x Dorset ewes in which seasonal anestrus is ill-defined. Each breed received 10 d of progestagen priming before being subdivided into 3 groups. In Group L+G, 5 lactating ewes received GnRH (250 ng/h sc) for 96 h; in Group D+G, 5 dry ewes received GnRH (250 ng/h sc) for 96 h; in Group L, 5 lactating ewes received saline vehicle for 96 h. The infusions began when lactating and dry ewes were approximately 28 d and 120 d post partum, respectively. Blood samples were collected for LH, progesterone and estradiol analysis. Estrous behavior was monitored between Day -4 and Day +7. On Day +7 the reproductive tract was also examined. In the Mule ewes the mean plasma LH concentration increased (P<0.05) followingminipump insertion in each treatment group, although mean LH levels were greater (P<0.05) in Group D+G, than in either Group L+G or Group L. Following the GnRH infusion, mean plasma estradiol levels increased (P<0.05) in Group D+G but not in Group L+G. A preovulatory LH surge and subsequent ovulation occurred in 5/5, 2/5 and 0/5 ewes from Group D+G, L+G and L, respectively, and estrus was recorded in 5/5, 1/5 and 0/5 of these ewes, respectively. The LH surges began earlier (P<0.05) (43.2+/-6.8 h vs 77.0+/-1.0 h) and the ovulation rate was greater (2.2+/-0.37 vs 1.00+/-0.00) in Group D+G than Group LS-G. In the Finn x Dorset ewes mean LH concentrations increased (P<0.05), to a similar level following minipump insertion in Groups D+G and L+G, but not Group L. The elevated LH levels were accompanied by increased (P<0.05) plasma estradiol levels in Group D+G, but not in Group LI-G. The GnRH infusion culminated in an LH surge and estrous behavior in 5/5, 1/5 and 0/5 ewes from Groups D+G, L+D and L, respectively. The interval to the LH surge was similar between Group D+G (48.4+/-6.6 h) and Group L+G (46.0 h). Ovulation was evident in those ewes which exhibited an LH surge plusone additional ewe from Group L+G. The mean ovulation rate was greater in Group D+G (4.00+/-1.05) than in Group L+G (1.5+/-0.50). These data show that continuous GnRH infusion can consistently induce out of season breeding in the nonlactating Mule and Finn x Dorset ewe but can not break combined seasonal and lactational anestrous in these breeds. Further, between-breed differences are evident in the site along the hypothalamic-pituitary-ovarian axis at which reproduction is compromised in ewes at the same chronological stage post partum.

ASDD Area Sistemi Dipartimentali e Documentali, Università di Bologna, Catalogo delle riviste ed altri periodici
Documento generato il 12/07/20 alle ore 06:35:09