Endocrine Profiles Associated with Life Span of Induced Corpora Lutea in Postpartum Beef Cows

Abstract

Two experiments were designed to examine whether hormonal profiles were related to luteal life span in pluriparous postpartum anestrous beef cows. Cows (Exp. 1, n = 34; Exp. 2, n = 23) received norgestomet (N) for 9 d or served as controls (C). Each cow received 1,000 IU human chorionic gonadotropin (hCG) 48 h after removal of N (d 0). Blood samples collected every 15 min for 8 h on d -5, 3 and 5 (Exp. 1) or on d -10 and -1 (Exp. 2) were assayed for luteinizing hormone (LH) and follicle stimulating hormone (FSH). Cortisol was determined in hourly samples collected on d -5 and in samples collected every 2 min during suckling on the same day (Exp. 1). Concentrations of 15-keto-13,14-dihydro-PGF2 alpha (PGFM) were determined in samples collected at 15-min intervals for 2 h on d -5, 3, 5 and 10 (Exp. 1). Estradiol-17 beta was measured in samples collected on d -5 (Exp. 1) or on d -10 and -1 (Exp. 2). Life span of induced corpora lutea was longer (P less than .05) in N than C cows. Percentages of N cows in which corpora lutea, formed in response to hCG, exhibited a normal life span were 83% on farm 1 and 25% on farm 2 (Exp. 1), and 90% (Exp. 2), compared with 0% in C cows. Concentrations of FSH were not affected by N but were lower (P less than .05) on d -5 in cows on farm 2 (.6 +/- .1 ng/ml) than in cows on farm 1 (.8 +/- .1 ng/ml). On d -5, a treatment X farm interaction (P less than .05) for mean LH was observed and frequency of pulses of LH was higher (P less than .01) in N than C cows (2.7 +/- .4 vs. .8 +/- .8 pulses/8 h). Neither cortisol nor PGFM was affected by N. Estradiol was increased in d -1 (6.1 +/- .5 vs 2.6 +/- .8 pg/ml; P less than .01) by N. It is suggested that pre-treatment with N enhanced life span of induced corpora lutea, in part, by influencing secretion of LH and development of follicles, but a threshold concentration of FSH was required for N to exert this effect.

Development of preovulatory follicles expected to form short-lived corpora lutea in beef cows

“…However, Manns et al (1983) measured peripheral serum concentrations of 15-keto-13,14-dihydro-PGF-2a as an indicator of PGF-2a release and did not observe any pulses of this metabolite during regression of short-lived corpora lutea that would be expected to occur during normal luteal regression. These data can be interpreted to indicate that short-lived corpora lutea are more sensitive to (Wilks et al, 1976;Stouffer & Hodgen, 1980;Ramirez-Godinez et al, 1982a;Garcia-Winder et al, 1986) when compared to the follicular phase of a normal length cycle. Additionally, the concentration of oestradiol-17ß in follicular fluid of Type F follicles was~25% that in Type C follicles.…”

“…Progestagen pretreatment of anoestrous cows induced to ovulate with exogenous gonadotrophin-releasing hormone (GnRH) or human chorionic gonadotrophin (hCG) resulted in higher serum concentrations of oestradiol-17ß during the follicular phase than in cows not pre¬ treated with a progestagen (Sheffel et al, 1982;Garcia-Winder et al, 1986). Lower circulating concentrations of follicle-stimulating hormone (FSH) have been observed during the follicular phase in cows (Ramirez-Godinez et al, 1982a) and primates (Stouffer & Hodgen, 1980) preceding the formation of a short-lived corpus luteum.…”

Efeito do eCG ou benzoato de estradiol associado ao norgestomet na taxa de concepção de vacas de corte submetidas à IATF no pós-parto

“…14,15 Alguns autores reportaram que 30 dias após o parto ocorre um aumento na liberação de GnRH e consequentemente nos pulsos de LH. 16 O aumento na pulsatilidade de LH é necessário para que os folículos adquiram dominância e capacidade de secretarem grandes quantidades de E 2 , evento fisiológico determinante do "feedback" positivo no hipotálamo. 9,17 Vacas de corte, com boa condição corporal, possuem um intervalo de 27 a 37 dias entre o parto e a primeira ovulação.…”

“…O tratamento com Norgestomet aumentou a freqüência dos pulsos de LH 19 , as concentrações de E 2 no soro sangüíneo 16,20 e no fluído folicular 19 . Além disso, tais hormônios promoveram um "priming" no útero que previniram a ocorrência de ciclos interovulatórios de curta duração.…”

Effect of active immunization of pre-partum and post-partum cows against prostaglandin F-2 on lifespan and progesterone secretion of short-lived corpora lutea

“…Furthermore, corpora lutea having short lifespans occur after early weaning of calves from anoestrous cows (Odde et al, 1980;Copelin et al, 1987) and after ovulations induced by gonadotrophin-releasing hormone (GnRH) or human chorionic gonadotrophin during the early post-partum period in cattle (Lishman et al, 1979;Pratt et al, 1982;Garcia-Winder et al, 1986). The physiological importance of short-lived corpora lutea is unknown.…”