Control of gonadotrophin release in Scottish Blackface and Finnish Landrace ewes during seasonal anoestrus

Section: Short-term Studysupporting

confidence: 89%

Season influences FSH concentration in ovariectomized Ile-de-France ewes

Montgomery¹,

Martin²,

Blanc³

et al. 1987

“…This, at first glance, seems inconsistent with the results of previous studies (McNatty et al, 1989) in which mean daily FSH and LH concentrations were found overall to be significantly higher in FF than in ++ ovariectomized ewes. However, in these animals the genotypic differences were obvious only in the frequency of higher FSH and LH values in FF compared to ++ ewes over a long (i.e. (Webb et al, 1985a). Although Booroola FF ewes are more likely to have a higher fequency of elevated FSH and LH concentrations compared to ++ ewes (McNatty et al, , 1989, as is the case for Finnish Landrace compared to Scottish Blackface ewes (Webb et al, 1985a), the mechanisms which underly these differences may not be the same.…”

Section: Discussionmentioning

confidence: 87%

“…However, it is not known whether F gene-specific differences exist in the sensitivity of the hypothalamic-pituitary axis to oestradiol, progesterone or other ovarian hormones. The highly fecund Finnish Landrace ewe is known to be less sensitive to oestradiol negative feedback than the less fecund Scottish Blackface ewe as assessed by the plasma concentrations of follicle-stimulating hormone (FSH) and luteinizing hormone (LH) (Webb et al, 1985a). Ovarian hormones other than oestradiol or progesterone also contribute to pedigree analysis: these genotypic classifications were confirmed by laparoscopy according to the criteria of Davis et al (1982).…”

Section: Introductionmentioning

confidence: 99%

Effects of oestradiol-17 , progesterone or bovine follicular fluid on the plasma concentrations of FSH and LH in ovariectomized Booroola ewes which were homozygous carriers or non-carriers of a fecundity gene

McNatty

Hudson²,

Collins³

et al. 1989

Summary. The although there were significant effects of the steroids and bFF with respect to dose (P < 0\m=.\05). At 6 days after steroid implantation, no gene-specific effects were noted for the plasma concentrations of FSH although significant effects of dose of oestradiol (P < 0\m=.\01) but not progesterone were noted. Also at 6 days after steroid implantation, no gene-specific differences in the pulsatile patterns (i.e. peak frequency or amplitude) of plasma LH concentrations were noted although there were significant effects of steroid dose (P < 0\m=.\05) on frequency and/or amplitude.It is concluded that the higher ovulation-rate in FF than ++ Booroola ewes is unlikely to be due to gene-specific differences in the sensitivity of the hypothalamic\p=n-\ pituitary axis to ovarian hormones.

“…The concentrations of FSH and LH in the plasma samples were measured using radioimmunoassays. Details of the LH assay modified in this laboratory have been described previously (Martensz et al, 1976;Webb et al, 1985b). Plasma FSH concentrations were measured by an homologous assay supplied by NIAMDD.…”

Section: Methodsmentioning

confidence: 99%

“…The differences in mean concentrations of gonadotrophins between the two selected lines during the periods of frequent blood sampling were investigated by analysis of variance after log transformation. The method of analysis used for the LH pulse frequency and amplitude has previously been described in detail (Webb et al, 1985b).…”

Section: Methodsmentioning

confidence: 99%

Changes in the feedback control of gonadotrophin secretion in ewes from lines selected for testis size in the ram lamb

McNeilly

Fordyce²,

Land³

et al. 1988

Self Cite

Summary. The dynamics of FSH and LH secretion were studied in sheep genetically selected for High (H) and Low (L) rates of testis growth. Gonadotrophin secretion had previously been shown to be affected in the ram lamb with H-line lambs more sensitive to steroid feedback than L. While there were significant differences in mean LH concentrations during the luteal and follicular phases of the oestrous cycle, mean LH values were essentially similar in the two lines in response to ovariectomy, the effect of oestradiol implants on the response to ovariectomy and the response to LHRH. However, the frequency of LH pulses in the H line was similar during both phases of the oestrous cycle, showing a surprising insensitivity to steroid feedback. By contrast, LH pulse frequency was markedly lower in the L-line ewes in the luteal than the follicular phase (0\m=.\6 vs 1\m=.\1 pulses/h) as expected from the literature. Mean FSH concentrations were significantly higher in the L-line ewes during the follicular phase of the oestrous cycle and after ovariectomy but no significant differences were detected at the other sampling periods. There were no differences in ovulation rate between the lines.It was concluded that selection for testis size had affected the feedback control of gonadotrophin release in the ewe, as in the ram, and hence the expression of the genes controlling this is not sex limited.