Gas/Liquid Chromatography–Mass Spectrometry Analysis of Key Functional Substances Regulating Poll Gland Secretion in Male Camels during Seasonal Estrus

SIMPLE SUMMARY: A gas/liquid chromatography–mass spectrometry (GC/LC-MS) dual platform was used to determine the chemical composition of poll gland secretions from the neck manes of male Bactrian camels during estrus, and then steroids and neurochemicals were identified as the key functional substances for regulating seasonal estrus in male camels. The results make a significant contribution to the literature because despite the low reproductive performance of these economically and scientifically important animals, studies on the chemical composition and physiological functions of poll gland secretions in Bactrian camels are very rare. This is the first study to employ a GC/LC-MS dual platform to provide an unbiased global metabolite profile of male Bactrian poll gland secretions. Our findings provide important insights into the development and function of poll glands in Bactrian camels. ABSTRACT: Increased poll gland secretion is a major characteristic and indicator of estrus in male Bactrian camels; however, research on these poll glands and their secretion is extremely rare. In this study, we determine the chemical composition of poll gland secretions and identify the key functional substances that regulate seasonal estrus in male camels. A GC/LC-MS dual platform was used to analyze ventral hair (control) and neck mane samples containing poll gland secretions from male Bactrian camels during estrus. Multidimensional and single-dimensional analyses were used to screen differentially expressed metabolites (DEMs) between groups. Functional prediction of enriched metabolites was performed using a Human Metabolome Database comparison and Kyoto Encyclopedia of Genes and Genomes pathway enrichment analysis, which were then compared with a behavioral analysis of male Bactrian camels in estrus. A total of 1172 DEMs and 34 differential metabolic pathways were identified. One metabolite group was found to relate to steroid synthesis and metabolism, and another metabolite group was associated with neural metabolism. Therefore, we speculate that steroids and neurochemicals jointly regulate estrous behavior in male Bactrian camels, thus providing theoretical insights into the development and function of poll glands in Bactrian camels.