Progesterone Levels Following Treatment of Seasonally Anoestrous Ewes With Synthetic Lh-Releasing Hormone

Abstract

Summary. Plasma progesterone determinations were carried out on blood samples collected daily from Clun Forest ewes during the normal oestrous cycle and also after administration of LH-releasing hormone (LH-RH) during seasonal anoestrus.Levels of plasma progesterone at oestrus ranged from 0\m=.\1to 0\m=.\5 ng/ml and luteal phase levels from 3 to 6 ng/ml. Levels found during seasonal anoestrus were within the range of those observed at oestrus. Following treatment with LH-RH, there was an increase in the plasma LH level in all cases and ovulation occurred in twenty-three out of twenty-seven treated ewes. In the animals which ovulated, the plasma progesterone concentration either remained basal (eighteen animals) or rose to a lower level (<2 ng/ml) than that found during the luteal phase of the cycle.

Response of ewes to a single injection of an analogue of PGF-2 given at different stages of the oestrous cycle

“…injection of 100 µg of the PGF-2a analogue, ICI 80,996, given to ewes between Days 5 and 8 of the oestrous cycle, caused rapid luteolysis and resulted in well synchronized behavioural oestrus (Acritopoulou, Haresign, Foster & Lamming, 1977), but response to treat¬ ment at other stages of the cycle was not studied. The Plasma progesterone concentrations were measured in the 2 h (10 ml) and daily samples by the radioimmunoassay described by Haresign, Foster, Haynes, Crighton & Lamming (1975). The degree of cross-reaction with other major steroids in sheep plasma was < 1%, the sensitivity of the assay was 0-08 ng/ml plasma and the inter-and intra-assay coefficients of variation in this study were both <10%.…”

Response of cyclic and post-partum suckled cows to injections of synthetic LH-RH

“…Three separate cow plasma samples were assayed at dilutions of 1:1, 1:2, 1:4, 1:8, 1:16 and the linear regression lines were parallel. The intra-assay coefficient of variation for randomly selected duplicate pairs, calculated by the method of Snedecor (1952) Plasma progesterone was determined by the technique described for sheep plasma (Haresign, Foster, Haynes, Crighton & Lamming, 1975). Water blanks were 25-9 ± 6-0 (S.E.M.)…”

Response of sows to oestradiol benzoate treatment after weaning at two stages of lactation

“…Blood samples were analysed for LH (Foxcroft, Pomerantz & Nalbandov, 1975), FSH and oestradiol-17ß (Foxcroft, Elsaesser, Stickney, Back & Haynes, 1983) and progesterone (Haresign, Foster, Haynes, Crighton & Lamming, 1975) by previously validated radioimmunoassays. Interand intra-assay coefficients of variation (CV) were 12 and 6% and 15 and 4% for LH and FSH respectively.…”