Effect of feeding olive-pulp silage on the seminal characteristics and fatty acid profile of the sperm plasma membrane in Iranian fat-tailed sheep

This study was conducted to investigate the effect of feeding high levels of olive-pulp silage on the seminal characteristics of Ghezel and Mehraban sheep. Sixteen fertile rams (3.5-4.0 years of age) of the Ghezel or Mehraban breeds (8 rams per breed) were randomly assigned to diets containing 70% olive-pulp or corn silage for 120 days. Semen was collected every 3 weeks by electro-ejaculation. Seminal volume, sperm density, sperm forward motility, sperm numbers, the percentage live sperm, acrosomal integrity, and sperm abnormalities were evaluated immediately after semen collection. The concentration of the seminal malondialdehyde (MDA) was also recorded. Serum testosterone concentrations were determined by ELISA for samples collected monthly. The profile of fatty acids in the sperm plasma membrane of the Mehraban rams was determined by gas chromatography, using samples of semen collected on days 0 and 120. The diet by time interaction significantly (P < 0.01) affected the seminal volume, sperm density, sperm number, and MDA concentration. The diet × breed × time interaction was also significant (P < 0.01) for sperm density, the percentage live sperm, sperm forward motility, and percentage sperm with normal acrosomes. However, the breed × diet interaction did not have a significant effect on the parameters investigated, other than semen volume. The diet significantly affected the percentage of palmitic, oleic, pentadecanoic, and docosahexaenoic acid in the sperm plasma membrane. Other saturated and unsaturated fatty acids were not significantly affected by the type of silage fed to Mehraban rams. The results indicated that a diet containing 70% olive-pulp silage and 30% alfalfa hay did not have a detrimental effect on the reproductive parameters of Ghezel and Mehraban rams when fed for up to 120 days. On the other hand, it increased the percentage of unsaturated fatty acids in the sperm membrane. Being a cheap by-product, olive-pulp can be economical to feed to mature rams for extended periods of time, without having any detrimental effect on sperm quality.