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To develop successful ex-situ breeding programs for the conservation of threatened wildlife, an understanding of reproductive endocrinology in the species of interest is essential. Fecal hormone metabolite patterns are widely used in this regard, but limited information is available regarding how these reflect blood hormone profiles. This study aimed to longitudinally monitor and compare circulating progestagen (sP) and estrogen (sE) concentrations, as well as fecal progestagen (fPM) and estrogen (fEM) metabolite concentrations with observed reproductive behaviors of African lionesses. For 18 months, blood sampling (n = 309) from five captive lionesses took place 1–7 times per week during positive reinforcement training. In parallel, over a period of 9 months, fecal samples (n = 129) from four of these lionesses were searched for daily and collected when found. Daily behavioral monitoring of all females enabled classification of reproductive stage according to presence/absence of characteristic behavioral events (i.e., “allowing mount”, “copulation”, “flirting run”, “lordosis”, “purring”, and “rolling”). Competitive enzyme immunoassays were used for steroid quantification. In total, 11 an-ovulatory and 16 ovulatory cycles (7 pregnancies and 9 pseudo-pregnancies) were assessed. When compared, the pattern of fecal hormone metabolite concentrations matched reproductive behavior more reliably than circulating steroid concentrations. Both sP and fPM patterns were correlated (n = 51; r = 0.86) and enabled identification of luteal phases, which helped to distinguish between pregnant and non-pregnant females. In contrast, detection of estrus by measurement of sE and fEM was not accurate regardless of the matrix evaluated.

On their way to the oocyte, sperm cells are subjected to oxidative stress, which may trigger the oxidation of phospholipids (PL). Applying MALDI-TOF MS, HPTLC and ESI-IT MS, we comparatively analyzed the PL compositions of semen and blood of species differing in their reproductive systems and types of nutrition (bull, boar, stallion, lion and man) with regard to the sensitivity to oxidation as well as the accumulation of harmful lyso-PL (LPL), transient products of lipid oxidation. In addition, the protective capacity of seminal fluid (SF) was also examined. The PL composition of erythrocytes and blood plasma is similar across the species, while pronounced differences exist for sperm and SF. Since the blood function is largely conserved across mammalian species, but the reproductive systems may vary in many aspects, the obtained results suggest that the PL composition is not determined by the type of nutrition, but by the relatedness of species and by functional requirements of cell membranes such as fluidity. Sperm motion and fertilization of oocytes require a rather flexible membrane, which is accomplished by significant moieties of unsaturated fatty acyl residues in sperm lipids of most species, but implies a higher risk of oxidation. Due to a high content of plasmalogens (alkenyl ether lipids), bull sperm are most susceptible to oxidation. Our data indicate that bull sperm possess the most effective protective power in SF. Obviously, a co-evolution of PL composition and protective mechanisms has occurred in semen and is related to the reproductive characteristics. Although the protective capacity in human SF seems well developed, we recorded the most pronounced individual contaminations with LPL in human semen. Probably, massive oxidative challenges related to lifestyle factors interfere with natural conditions.

On their way to the oocyte, sperm cells are subjected to oxidative stress, which may trigger the oxidation of phospholipids (PL). Applying MALDI-TOF MS, HPTLC and ESI-IT MS, we comparatively analyzed the PL compositions of semen and blood of species differing in their reproductive systems and types of nutrition (bull, boar, stallion, lion and man) with regard to the sensitivity to oxidation as well as the accumulation of harmful lyso-PL (LPL), transient products of lipid oxidation. In addition, the protective capacity of seminal fluid (SF) was also examined. The PL composition of erythrocytes and blood plasma is similar across the species, while pronounced differences exist for sperm and SF. Since the blood function is largely conserved across mammalian species, but the reproductive systems may vary in many aspects, the obtained results suggest that the PL composition is not determined by the type of nutrition, but by the relatedness of species and by functional requirements of cell membranes such as fluidity. Sperm motion and fertilization of oocytes require a rather flexible membrane, which is accomplished by significant moieties of unsaturated fatty acyl residues in sperm lipids of most species, but implies a higher risk of oxidation. Due to a high content of plasmalogens (alkenyl ether lipids), bull sperm are most susceptible to oxidation. Our data indicate that bull sperm possess the most effective protective power in SF. Obviously, a co-evolution of PL composition and protective mechanisms has occurred in semen and is related to the reproductive characteristics. Although the protective capacity in human SF seems well developed, we recorded the most pronounced individual contaminations with LPL in human semen. Probably, massive oxidative challenges related to lifestyle factors interfere with natural conditions.