Measurement of faecal estrone sulphate by enzymeimmunoassay was evaluated as a non-invasive means of monitoring pregnancy status in mares. Faecal samples from non-pregnant mares had a mean ± s.e.m. estrone sulphate concentration of 23 ± 0.9 ng/g (N=242). In pregnant mares, mean faecal estrone sulphate concentrations increased progressively during the first half of gestation. The values rose from a mean ± s.e.m. of 49 ± 4 ng/g (N=121) for samples collected <80 days post-mating, to 122 ± 9 ng/g (N=30) for samples collected 161 to 180 days post-mating. Thereafter, faecal estrone sulphate concentrations remained relatively constant for the remainder of pregnancy. From 150 days post-mating onwards, <2% of faecal samples from pregnant mares had an estrone sulphate concentration below 66 ng/g which was the value 3 standard deviations above the mean value found for non-pregnant mares. Following foaling or foetal death, faecal estrone sulphate concentrations returned quickly to non-pregnant levels. Using this estrone sulphate enzymeimmunoassay, mares may be confirmed pregnant once faecal estrone sulphate concentrations rise above the 66 ng/g cut-off value. Those mares in which faecal estrone sulphate concentrations have not risen above 66 ng/g by 150 days post-mating may be considered to be non-pregnant. Measurement of faecal estrone sulphate thus offers a convenient, non-invasive means of monitoring pregnancy status.
Proceedings of the New Zealand Society of Animal Production, Volume 57, , 234-236, 1997
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