Effect of the body condition of ewes on the secretion of LH and FSH and the pituitary response to gonadotrophin-releasing hormone

Abstract

The effects of body fat content (body condition) of ewes on hypothalamic activity and gonadotrophin-releasing hormone (GnRH) secretion and on pituitary sensitivity to GnRH were investigated using Scottish Blackface ewes. Two groups of 12 ewes were fed so that they achieved either a high body condition score (2.98, S.E.M. = 0.046; approximately 27% of empty body weight as fat) or a low body condition score (1.94, S.E.M. = 0.031; approximately 19% of empty body weight as fat) by 4 weeks before the period of study. Thereafter, they were differentially fed so that the difference in mean condition score was maintained. Oestrus was synchronized, and on day 11 of the subsequent cycle half of the ewes of each group were ovariectomized. On day 12, the remaining ewes were injected (i.m.) with 100 micrograms prostaglandin F2 alpha analogue and ovariectomized 30 h later. Numbers of large ovarian follicles and corpora lutea present at ovariectomy were recorded. Blood samples were collected at 15-min intervals for 12 h on day 10 of the cycle (luteal phase) and at 10-min intervals from 24 to 30 h after prostaglandin injection (follicular phase). At days 2 and 7 after ovariectomy, samples were collected at 15-min intervals for 8 h and ewes were then injected with 10 micrograms GnRH and samples were collected for a further 3 h.(ABSTRACT TRUNCATED AT 250 WORDS)

Winter Body Condition of Moose (Alces Alces) in a Declining Population in Northeastern Minnesota

“…Although BCS systems are somewhat limited by an inherent subjectivity, benefits relative to the nutrition, health, and reproduction of domestic livestock have been documented (Wildman et al, 1982;Gunn et al, 1984;Rhind et al, 1989;Otto et al, 1991;Ruegg, 1991). Overall practicality for fieldwork; the ability to make condition assessments on live animals (i.e., no need to sacrifice); quick, reliable identification of ''extremes of nutritional status''; and providing an index of stored energy have been cited as advantages of BCS techniques for free-ranging animals (Franzmann, 1985;Gerhart et al, 1996).…”

Management Factors Affecting Fertility in Sheep

“…Body condition score (BCS) has proved useful as a management tool for subjectively assessing the nutritional status of ewes. In this way, body condition directly affects hypothalamic activity and GnRH secretion, but not pituitary sensitivity to GnRH, and these effects on reproductive performance are also mediated through changes in ovarian hormones or in hypothalamo-pituitary sensitivity to ovarian hormones (Rhind, et al, 1989). The effect of body condition on the ovulation rate of ewes has been extensively reported (Ducker & Boyd, 1977;Morley, et al, 1978;Adalsteinsson, 1979;.…”

“…The effect of body condition on the ovulation rate of ewes has been extensively reported (Ducker & Boyd, 1977;Morley, et al, 1978;Adalsteinsson, 1979;. High body condition score has been associated with an increase of ovulation (Rhind, et al, 1989;Xu, et al, 1989), especially in Mediterranean breeds at the beginning of the breeding season (Forcada, et al, 1992). Most authors recommend a BCS of 2.5 to 3.0 either for natural or artificially breeding (Contreras-Solis, et al, 2009;Husein & Ababneh, 2008).…”

FSH-stimulated follicle development in ewes in high and low body condition and chronically treated with gonadotrophin-releasing hormone agonist

“…Ewes in high body condition have a higher rate of repro¬ ductive performance than ewes in low body condition as a result of their greater ovulation rate (Gunn, 1983 (Rhind and McNeilly, 1986;Rhind et al, 1989). FSH has an essential role in the development of follicles tô 2.5 mm diameter , but differences in follicle populations and ovulation rate associated with differ¬ ences in body condition are not consistently associated with differences in circulating FSH concentrations (Findlay and Cumming, 1976; Rhind and McNeilly, 1986;Rhind et al, 1989).…”

“…FSH has an essential role in the development of follicles tô 2.5 mm diameter , but differences in follicle populations and ovulation rate associated with differ¬ ences in body condition are not consistently associated with differences in circulating FSH concentrations (Findlay and Cumming, 1976; Rhind and McNeilly, 1986;Rhind et al, 1989). It was therefore postulated that differences in the pattern of follicle development associated with differences in body con¬ dition may be attributable to differences in the response of small ovarian follicles ( < 2.5 mm diameter) to FSH stimulation.…”