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Evaluation of steroid concentrations in the saliva of pre-pubertal gilts for the identification of biomarkers of the pubertal stage of maturity
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Estrus synchronization is important for optimal management of gilt reproduction in farms. Synthetic progestogens are used for this purpose, but there is growing demand for non-hormonal alternatives.Before puberty, gilts exhibit a “waiting period”, related to ovarian development and gonadotrophin secretions, during which external stimulation, such as boar exposure, could induce and synchronize first ovulation. Practical non-invasive tools for identification of this period in farms are lacking. During this period, urinaryestrone levels are high, but urine sampling is difficult in group-housed females. Our aim was to search for steroidal biomarkers of this “waiting period” from immature to pubertal gilts through saliva monitoring. Six 144-to 147-day-old Large White gilts were subjected to ultrasound puberty diagnosis 3 times a week until firstovulation. Urine and saliva samples were collected at the same frequency for estrone assay and steroidome analysis respectively. Data were analyzed using the R software (nonparametric permutation test). Urinary estrone concentration significantly increased 2 weeks before puberty (detected at 182–192 days). Steroidomeanalysis quantified 28 steroids in saliva. Significant variations were detected within 2 weeks before puberty for dehydroepiandrosterone (decrease) and estradiol-17b (increase). These steroids could be biomarkers of the “waiting period”. These results confirm that non-invasive salivary sampling could allow the identification of thephysiological status of the gilts and presumably the optimal time for application of the boar effect.