Bioassay of Oestrogen Using Sheep

Lamond,; Southcott, W. H.

doi:10.1071/bi9620379

Cited by 9 publications

(3 citation statements)

References 15 publications

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“…Regression equations for quantal data were calculated by the method of Bliss & Marks (1939), while regression analyses weighted for unequal subclass numbers were used for continuous variables. The values of difference characteristics of oestrous behaviour as end-points for oestrogen assay were compared using the index of precision ( ) (Lamond & Southcott, 1962).…”

Section: Analysis Of Resultsmentioning

confidence: 99%

Effect of Oestrogen on Oestrous Behaviour and Its Variation With Season in the Ewe

Fletcher¹,

Lindsay²

1971

Journal of Endocrinology

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The effects of dose of oestrogen and season on the expression of oestrous behaviour was studied in 60 spayed and 16 intact ewes.In progesterone-primed spayed ewes the incidence and duration of oestrous behaviour increased and the interval between injection of oestrogen, and onset of oestrous behaviour decreased as the dose of oestrogen was increased. The linear regression of duration of oestrus on log dose of injected oestrogen provided the most precise measure of the effect of changing dose level of oestrogen on oestrous behaviour.The sensitivity of spayed ewes to constant levels of oestrogen increased to a maximum near the middle of the breeding season and then declined to a minimum during the non-breeding season. In progesterone-synchronized intact ewes the interval between the end of progesterone treatment and onset of oestrus was at a minimum, and duration of oestrus at a maximum, near the middle of the breeding season. By bioassay it was estimated that endogenous oestrogen production was greater near the middle ofthe breeding season than at either the beginning or end.It is concluded that seasonal variation in the expression of oestrous behaviour in intact ewes is controlled by changes in both the production of endogenous oestrogen and the sensitivity of ewes to it.

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Section: Analysis Of Resultsmentioning

confidence: 99%

Effect of Oestrogen on Oestrous Behaviour and Its Variation With Season in the Ewe

Fletcher¹,

Lindsay²

1971

Journal of Endocrinology

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“…Lamond and Southcott (1962) showed that the uterine weight increase after administration of stilboestrol could be the basis of a useful assay, and Davies and Bennett (1962) used the assay in assessing differences in oestrogenic potency between subterranean clover varieties (Trifolium subterraneum). Braden, Southcott, and Moule (1964) examined the increase in teat length in wethers and ovariectomized ewes after oestrogenic stimulation, and concluded that the response could be used for detecting oestrogens in pasture and under certain circumstances would also provide a measure of the oestrogenic potency.…”

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confidence: 99%

Investigation of the vaginal smear (Allen-Doisy) assay of oestrogen in ovariectomized ewes

Lamond¹,

Lang²

1965

Aust. J. Agric. Res.

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The vaginal smear (Allen-Doisy) assay for oestrogens has been studied with ovariectomized ewes. Variation between ewes was considerable and the slopes of the log dose-response lines were low. The value of the assay for quantitative determination of oestrogen is limited by lack of precision. The oestrogenic content of red clover (Trifolium pratense) was estimated in terms of micrograms of injected stilboestrol per kilogram of dry matter.Considerable variation in sensitivity to the standard was observed. Intraruminal administration of stilboestrol reduced its activity about 100-fold compared with subcutaneous administration. Ewes were given carbon tetrachloride to cause liver damage but the vaginal response to red clover was not altered.The increasing importance of pasture oestrogens in reproduction in ewes (Moule, Braden, and Lamond 1963) has prompted investigation of methods of bioassay of oestrogenic pasture by using sheep. Lamond and Southcott (1962) showed that the uterine weight increase after administration of stilboestrol could be the basis of a useful assay, and Davies and Bennett (1962) used the assay in assessing differences in oestrogenic potency between subterranean clover varieties (Trifolium subterraneum). Braden, Southcott, and Moule (1964) examined the increase in teat length in wethers and ovariectomized ewes after oestrogenic stimulation, and concluded that the response could be used for detecting oestrogens in pasture and under certain circumstances would also provide a measure of the oestrogenic potency. Morley, Bennett, and Axelson (personal communication) have found that mammary gland growth and a lactation score in ewes may be related to dose of oestrogen. Since the vaginal smear (Allen-Doisy) assay depends on a response that is qualitatively accurate (substances other than oestrogen may influence uterine, teat, and mammary gland growth) it was decided to examine its value for quantitative assay of pasture oestrogens.

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“…In earlier studies the oestrogen content of clover was measured as responses from bioassay using small animals (see Moule et al 1963 Lamond and Southcott 1962;Davies and Bennett 1962;Braden et al 1964;Millington et al 1964a;Bennett and Dudzinski 1967;Lindsay and Francis 1968), but responses are still from short-term measurements. Secondly, for farm practice the Eong-term response (years.…”

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confidence: 99%

Factors Affecting the Oestrogen Content of Subterranean Clover Pastures

Rc¹

1970

Aust Veterinary J

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Bioassay of Oestrogen Using Sheep

Cited by 9 publications

References 15 publications

Effect of Oestrogen on Oestrous Behaviour and Its Variation With Season in the Ewe

Effect of Oestrogen on Oestrous Behaviour and Its Variation With Season in the Ewe

Investigation of the vaginal smear (Allen-Doisy) assay of oestrogen in ovariectomized ewes

Factors Affecting the Oestrogen Content of Subterranean Clover Pastures

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