Enzymeimmunoassay of oestrone sulphate concentrations in faeces for non-invasive pregnancy determination in mares.

AIM: To determine the suitability of measuring faecal oestrone sulphate (OS) by enzymeimmunoassay as a means of determining pregnancy status in mares bred under New Zealand conditions. METHODS: An antibody-coated microtitre plate-based enzymeimmunoassay was used to determine the concentration of OS in faecal and plasma samples obtained from pregnant and non-pregnant mares. RESULTS: In non-pregnant mares, the mean faecal OS concentration was 34 ng/g, and the value three standard deviations above this was 80 ng/g. None of 427 faecal samples collected from 116 non-pregnant mares over a l-year period had an OS concentration >80 ng/g. Only five samples from three mares had an OS concentration >65 ng/g, the value two standard deviations above the mean non-pregnant value. Analysis of faecal OS concentrations in 532 faecal samples collected from 39 pregnant mares showed that as pregnancy progressed, an increasing proportion of faecal samples had OS concentrations >80 ng/g. None of the mares 150 days or more pregnant had faecal OS concentrations <50 ng/g, and 204/220 samples obtained from these mares had faecal OS concentrations >80 ng/g. Following foaling or foetal death, elevated faecal OS concentrations returned quickly to non-pregnant levels. The mean +/- s.e.m. plasma level of OS in five mares bled daily throughout one oestrous cycle was 1.7 +/- 0.2 ng/ml. Sixty-eight blood samples from pregnant mares bled up to five times between 92 days after mating and foaling all had plasma OS concentrations >30 ng/ml, with 64/68 being >50 ng/ml. CONCLUSIONS: This study shows that measuring faecal OS concentrations by enzymeimmunoassay offers a convenient, accurate, non-invasive means of determining pregnancy status in mares from 150 days after mating onwards. Mares with faecal OS concentrations <50 ng/g can be considered not pregnant, while mares with faecal OS concentrations >80 ng/g can be considered pregnant. Those few mares returning a faecal OS concentration between 50 and 80 ng/g should be retested to obtain a conclusive result. Measuring plasma OS concentrations allows pregnancy status to be determined earlier (from 100 days after mating). Moreover, the discrimination between non-pregnant and pregnant levels is greater for OS in plasma than in faeces. CLINICAL RELEVANCE: Measurement of OS concentrations in faeces provides an alternative and non-invasive means of determining pregnancy status in mares from 150 days after mating.

Comparison of the merits of measuring equine chorionic gonadotrophin (eCG) and blood and faecal concentrations of oestrone sulphate for determining the pregnancy status of miniature horses.

The relative merits of measuring blood concentrations of equine chorionic gonadotrophin (eCG, previously known as pregnant mare serum gonadotrophin (PMSG)), or oestrone sulphate (OS), or faecal OS concentrations for determining pregnancy status in miniature horses were investigated. Pregnant mares between 40 and 140 days after mating had serum eCG concentrations > 1 I.U. mL-1, with the highest concentrations occurring between days 50 and 120. However, eCG measurements were susceptible to returning a 'false positive' diagnosis of pregnancy. Plasma OS concentrations ranged from 0.1 to 3.6 ng mL-1 in non-pregnant mares, whereas pregnant mares beyond 100 days post-mating all had plasma OS concentrations > 30 ng mL-1. Faecal OS concentrations ranged from 4 to 89 ng g-1 in non-pregnant mares. For faecal samples collected from pregnant mares 150 days or more after mating, 97% of samples had OS concentrations > 85 ng g-1, the value 3 standard deviations above the mean non-pregnant value. None had values below 67 ng g-1, the value 2 standard deviations above the mean non-pregnant value. These results show that measurement of eCG is suitable for determining pregnancy status in miniature mares between 40 and 100 days post-mating. However, mares returning a 'pregnant' diagnosis should undergo a blood OS test 100 or more days after mating to eliminate the possibility of a 'false positive' diagnosis. Measuring blood OS is recommended as the method of choice for determining pregnancy status in miniature mares 100 or more days after mating. Faecal OS measurements provide a non-invasive alternative to blood OS testing from 150 days post-mating. However, the discrimination between 'pregnant' and 'non-pregnant' levels of OS is not as great in faeces as it is in blood.

Inhibin production in vitro by granulosa cells from Booroola ewes which were either homozygous or non-carriers of a fecundity gene influencing their ovulation rate.

The production of inhibin by granulosa cells was studied in vitro using cells from follicles of various sizes and health. Follicles were recovered on Days 10-13 of the oestrous cycle, from Booroola x Romney ewes which were homozygous (FF) carriers or non-carriers (++) of the fecundity (F) gene. Inhibin was measured using a bioassay based on the suppression of follicle-stimulating hormone (FSH) output by cultured pituitary cells from ovariectomized Romney ewes and, in some instances, for comparative purposes, by radioimmunoassay also. Geometric mean inhibin production by granulosa cells from nonatretic follicles increased with increasing follicle diameter, during the first 24 h of culture, for both genotypes. The geometric mean production of inhibin by cells from nonatretic 3-4.5 mm diameter FF follicles (the largest follicles found in FF ewes), was significantly higher (P less than 0.05) than that by cells from non-atretic 3-4.5 mm diameter ++ follicles, but similar to that of cells from non-atretic greater than or equal to 5 mm diameter ++ follicles. The production of oestradiol-17 beta by cells cultured in the presence of testosterone (1 microgram/ml) followed a pattern similar to cellular inhibin production. There was a positive linear correlation between inhibin and oestradiol-17 beta production during the first 24 h of culture, for both genotypes. In addition to acting as a substrate for oestradiol-17 beta synthesis, testosterone generally had a slight, stimulatory effect on inhibin production.(ABSTRACT TRUNCATED AT 250 WORDS)

Oocyte production and ovarian steroid concentrations of immature rats in response to some commercial gonadotrophin preparations.

Four commercial gonadotrophin preparations, namely Folligon, F.S.H.-P., Folltropin and Ovagen, were examined for their effects on oocyte production and ovarian steroid concentrations in immature rats. The ratios of the FSH to LH concentrations of the preparations, determined by radioreceptor assays, were Folligon 5, F.S.H.-P. 18, Folltropin 49 and Ovagen 1090. Forty-eight hours after administering each gonadotrophin preparation to immature rats, ovulation was induced by injection of chorionic gonadotrophin. Twenty-four hours later, oocytes were recovered from the oviducts and counted. Oocytes were produced after injection of chorionic gonadotrophin following a single injection of Folligon (10-50 i.u.). However, no oocytes were produced in response to the other gonadotrophin preparations unless they were administered by continuous infusion (30-1000 micrograms day-1). When given by injection (Folligon) or infusion (others), the gonadotrophin preparations all promoted a dose-dependent increase in mean oocyte production, except at the highest doses when mean oocyte numbers either remained unchanged or declined significantly in the cases of Folligon and F.S.H.-P. The highest mean numbers of oocytes produced in response to Folltropin (48 +/- 9 oocytes, mean +/- s.e.m.) and Ovagen (47 +/- 7) were greater than those attained with Folligon (21 +/- 6) or F.S.H.-P. (31 +/- 5). Mean ovarian weights also increased in a dose-dependent fashion in response to each of the gonadotrophin preparations. Measurements of ovarian steroid concentrations 48 h after the onset of gonadotrophin treatment (i.e. immediately prior to ovulation induction with chorionic gonadotrophin) showed that the gonadotrophin preparations markedly influenced the ratios of ovarian oestradiol-17 beta and androgen (androstenedione plus testosterone) concentrations. At low doses the gonadotrophin preparations increased the ratio of oestradiol-17 beta to androgens, but at the highest doses, with the exception of Ovagen, the ratio was reduced relative to peak values. Co-infusion of ovine LH (NIADDK-oLH-25; 10-20 micrograms day-1) with Ovagen (250 micrograms day-1) or ovine FSH (10 micrograms day-1, NIADDK-oFSH-17), both low in LH content, increased the mean number of oocytes produced and also the ovarian oestradiol-17 beta:androgen concentration ratio. However, with 40 micrograms LH day-1, the oestradiol-17 beta:androgen ratio fell due to a continued increase in mean ovarian androgen concentrations and a decrease in mean ovarian oestradiol-17 beta concentration. The mean number of oocytes produced also fell significantly.(ABSTRACT TRUNCATED AT 400 WORDS)