Serum metabolome analysis in doe kids for the identification of biomarkers of sexual precocity

Success of first breeding is a major concern for goat breeders, since failure to fertilize does increases unproductive time and breeding costs. Fertility rates after artificial insemination of young goats are highly variable and rather low. Breeders generally breed does that are older than 5 months and weight more than 32 kg. However, sexual precocity is highly variable between does. Up to now, there is no known biomarker for sexual precocity. A better characterization of the pubertal stage of maturity could help optimizing time for first breeding. Our objective was to analyze the serum metabolome of doe kids, just before the first breeding, in order to characterize the pubertal stage of maturity and identify biomarkers of sexual precocity. Weekly blood sampling was performed on twenty 6-to 7-month-old does born in February for 5 weeks before their first contact with bucks in September. Progesterone assays and metabolome analysis using 1H Nuclear Magnetic Resonance Spectroscopy were performed on the serum samples. No spontaneous ovulatory cycle was observed before breeding based on progesterone assays. All does had reached the pubertal stage of maturity at breeding since all got pregnant. Metabolome analysis allowed the identification of 109 spectral bins in sera. Between week 1 and 5 preceding buck introduction, 32 buckets showed significant variations (t-test, p < 0.05): i.e. inosine, formate, lactate and creatinine decreased, while threonine, tryptophan, isoleucine and trimethylamine oxide significantly increased. Metabolites with significant variations between the 5 considered weeks could be biomarkers of sexual precocity; studies are in progress to identify them.