Peony seed meal supplementation enhances semen quality in aged Qinchuan bulls

Healthy Qinchuan bulls aged 8.5-9.5 years were selected and randomly divided into 6 groups based on 0%, 2%, 4%, 6%, 8%, and 10% dietary supplementation of peony seed meal for three months. Overall, linear motility (LM), progressive motility (PM), straight-line velocity (VSL), curvilinear velocity (VCL), and the percentage increase of all sperm grades (A to D) were affected (p<0.05) by the dietary supplementation. LM (29.5 vs. 24.1%), PM (69.4 vs. 60.0%), VLS (38.0 vs. 33.3 μm/s), and VCL (48.3 vs. 44.3 μm/s) were consistently higher in the 6% peony seed meal dietary supplementation groups than in the control group, respectively. A similar pattern was observed in the 8% group. Inversely to sperm grades C and D, grades A and B were higher in all treated groups than the control group, except for the 2% group in sperm grade A. Moreover, the levels of the enzymes Superoxide dismutase (SOD), catalase (CAT), glutathione reductase (GR; except for 2% peony seed group), and glutathione peroxidase (GSH-px) were higher than the control group. The level of malondialdehyde (MDA) was lower in all treated groups than in the control group. Dietary supplementation of 2-8% peony seed meal improves the semen quality of aged Qinchuan bulls.