Proteomic characterisation of serum during the breeding cycle in male bactrian camels

The duration of the breeding cycle in male Bactrian camels lasts 2-6 months, depending on geographical location, environmental conditions, nutritional parameters and health status. In China, the breeding cycle can span 4 months (December to March), except for this period libido is lost. Camels exhibit increased pacing and anxiety, and display morphological, behavioural and endocrinological peculiarities, including 16-25% weight loss due to suppressed appetite. Using label-free liquid chromatography-tandem mass spectrometry (LC-MS/MS) shotgun proteomics, we characterised the proteome at 4 key stages (pro-breeding, breeding, peak breeding and termination of breeding). We identified 210, 215, 220, 310 and 220 proteins in non-breeding (control) and breeding (stages 1 to 4) groups, respectively, of which 178 were common to all groups. Among these, 16, 20, 18 and 21 were differentially expressed (p <0.05), with 4, 9,11 and 11 up-regulated and 12,11, 7 and 10 down-regulated in stages 1 to 4, respectively. Among differentially expressed proteins, 15 up-regulated and 8 down-regulated proteins were altered along with the breeding cycle. This is the first label-free proteomic characterisation of the Bactrian camel serum proteome. The findings provide new insight into temporal differences in serum protein composition in male Bactrian camel serum during the breeding cycle.