| Summary: | <p>Abstract</p> <p>Background</p> <p>In mammals, the ovarian follicular reserve is highly variable between individuals and impacts strongly on ovarian function and fertility. Nowadays, the best endocrine marker of this reserve in human, mouse and cattle is the anti-Müllerian hormone (AMH). The objectives of this work were to determine whether AMH could be detected in the plasma of prepubertal ewe lambs and to assess its relationship with their fertility at a young age.</p> <p>Results</p> <p>Plasma was taken from 76 Rasa Aragonesa ewe lambs at 3.6 months of age for AMH determination. Simultaneously, 600 IU equine chorionic gonadotropin (eCG) was administered and the number of ovulations recorded 6 days later. AMH was detected in 93% of the lambs, and the concentrations were about 3–4-fold higher in ovulating than in non-ovulating lambs (<it>P</it> < 0.004). Ewes aged around 10 months were mated, giving an overall fertility of 29%, and those failing to conceive were mated again 4 months later. Fertility at first mating was significantly correlated with plasma AMH concentration at 3.6 months (Spearman’s ρ = 0.34; <it>P</it> < 0.01). To use plasma AMH concentration as a screening test, a value of 97 pg/mL was determined as the optimum cutoff value to predict fertility at first mating (sensitivity = 68.2%; specificity = 72.2%). Fertility at first mating was 34.8 percentage points higher in ewe lambs with an AMH ≥ 97 pg/mL than in those with lower AMH concentrations (50% vs. 15%; <it>P</it> < 0.001).</p> <p>Conclusions</p> <p>Plasma AMH concentration might be a reliable marker of the ovarian status of prepubertal ewe lambs, reflecting their ability to respond to eCG stimulation. A single AMH measurement performed on ewe lambs early in age could be useful to select for replacement ewes with a higher predicted fertility at first mating.</p>
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