Ovulation and Fertilization in the Lamb

Section: Discussionsupporting

confidence: 90%

Section: Introductionmentioning

confidence: 99%

Reproductive function in prepubertal lambs: ovulation, embryo development and ovarian steroidogenesis

Trounson¹,

Willadsen²,

Moor³

1977

“…From several studies on ovaries from lambs between 10 and 32 weeks of age it has been noted that they are able to secrete steroids, ovulate and produce fertilizable ova in response to PMSG and/or hCG (Mansour, 1959;Land & McGovern, 1968;Trounson et ai, 1977). The also Trounson et ai, 1977;Tassell et ai, 1978;Tassell & Kennedy, 1980 (Hillier, 1981).…”

Section: Discussionmentioning

confidence: 99%

Ovarian follicular activity in Booroola lambs with and without a fecundity gene

McNatty¹,

Lun²,

Heath³

et al. 1987

Summary. The ovaries of 3-month-old Booroola lambs which were heterozygous carriers of a major gene (F) influencing the ovulation rate in mature ewes (i.e. F + lambs) were compared to those ofsimilarly-aged Booroola lambs which were non\ x=req-\ carriers of the F-gene (i.e. ++ lambs). The ovaries of the F+ Booroola lambs were significantly lighter (P < 0\m=.\01) than those of ++ lambs even though the mean \ m=+-\ s.e.m. number of follicles (\ m=ge\ 1 mm diam.) in the F+ lambs was greater than that in the ++ lambs (i.e. F+ lambs, 30\m=.\2\ m=+-\ 2\ m=. \ 5follicles; ++ lambs, 18\m=.\4\m=+-\1\m=.\2follicles; P < 0\m=.\01).In granulosa cells from non-atretic follicles (\m=ge\1 mm diam.) from F+ and ++ Booroola lambs, FSH (NIAMDD-FSH-S16) doses of 100 and 1000 ng/ml caused significant stepwise increases (P < 0\m=.\05) in cyclic adenosine 3\m='\,5\m='\-monophosphate(cAMP) production compared to that achieved at FSH doses of 0 and 1 ng/ml or at any FSH dose in cells from atretic follicles. However, no significant differences in FSH-induced cAMP production were noted with regard to Booroola genotype or follicular diameter.None of the granulosa cell preparations from non-atretic follicles of 1\ p=n-\ 2\ m=. \ 5mm diameter from F+ lambs (N = 13) or from non-atretic follicles of 1\ p=n-\ 4\ m=. \ 5mm diameter from ++ lambs (N = 16) responded to LH (NIAMDD-LH-S24; 10 or 1000 ng/ml) to produce significantly more cAMP than did the controls. In contrast, the granulosa cell preparations from non-atretic follicles of 3\ p=n-\ 4\ m=. \ 5 mm diameter from F+ lambs (N = 4) and from non-atretic follicles of \m=ge\5 mm diameter of ++ lambs (N = 4) produced significantly more cAMP (P < 0\m=.\05) in response to LH (1000 and/or 10 ng/ml) relative to that in the controls. The theca interna from follicles of lambs of both genotypes had functional LH receptors as judged by the androstenedione responses to exogenous LH although no genotypic differences were noted.In F+ lambs, the follicular fluid concentrations of testosterone but not oestradiol (i.e. in 1\ p=n-\ 4\ m=. \ 5mm diam. follicles) and granulosa cell aromatase activity (i.e. in 3\ p=n-\ 3\ m=. \ 5mm diam. follicles) were significantly higher (both P < 0\m=.\05) than in corresponding follicles or cells from ++ lambs.Collectively the results suggest that the Booroola F-gene influences the composition and function of sheep ovaries before puberty.

“…The follicles are able to respond to exogenous gonadotrophins and ovulation may be induced (Mansour, 1959). If intrauterine insemination is used to bypass the cervical block, the eggs ovulated may be fertilized (Land & McGovern, 1968), and when transferred to adults at an appropriate stage of the oestrous cycle they develop normally (Trounson, Willadsen & Moor, 1977). The latter authors also demonstrated that the capacity of the lamb follicle to secrete oestrogen, testosterone and progesterone in vitro was similar to that of the adult.…”

Section: Genetic and Seasonal Variationmentioning

confidence: 97%

Reproduction in young sheep: some genetic and environmental sources of variation

Land¹

1978

Self Cite

Summary. 'The extent of genetic and environmental variation' in the development of reproduction in sheep is illustrated by examples with particular reference to variation among breeds and to the effects of photoperiod. The interactions between genetic and environmental effects are introduced ; these may be so great that genetic groups may reverse their ranking for rate of development in different environments. The 'physiology of puberty' is then discussed. The difficulty of separating puberty from seasonal variation is stressed, and a possible contrast is drawn between the physiological characteristics of genetic variation and those of environmental variation in reproductive development. Finally the physiological factors associated with sterility in young females are discussed; most studies, however, have been conducted during the time of year when adult females would also be expected to be sterile, so that conclusions are difficult and a 'missing link' cannot be identified.