Morphological and biochemical characteristics of Afshari and Afshari × Booroola Merino cross bred rams (cross-continental cross breeding) semen before and after cryopreservation

• Sperm concentration and progressive motility in Afshari rams were higher than those of Afshari × Booroola Merino rams.
• Total motility in frozen-thawed sperm was greater in Afshari than that of Afshari × Booroola Merino rams.
• Semen of Afshari ram, evolved in cold regions, is more resistant to freezing process.

The aim of the present experiment was to study the effect of cross-continental cross breeding on morphological and biochemical characteristics of Afshari and Afshari × Booroola Merino cross bred rams semen before and after cryopreservation. Semen samples were collected from ten mature and fertile rams (n = 5/breed) once per week for 8 weeks during the breeding season. The results showed no significant differences in ejaculate volume, pH, total motility, membrane integrity and percentage of abnormal sperm before cryopreservation between the two breeds (P > 0.05). Sperm concentration and progressive motility (3.98 ± 0.22 × 109 sperm/mL and 64.84 ± 1.64%, respectively) in Afshari rams were significantly higher than those of Afshari × Booroola Merino (1.83 ± 0.26 × 109 sperm/mL and 52.92 ± 1.94%, respectively) rams (P < 0.01). There were no significant differences in the level of Na+, K+, Ca++ and Lactate dehydrogenase enzyme (LDH) of seminal plasma as well as testosterone levels of plasma between the two breeds (P > 0.05). Total motility in frozen-thawed sperm was greater in Afshari (44.15 ± 4.15%) than that of Afshari × Booroola Merino cross bred (18.07 ± 4.80%) rams (P < 0.01). In conclusion, the two breeds were similar in semen characteristics except in sperm concentration and progressive motility before cryopreservation and total motility after freezing- thawing. It is assumed that semen of Afshari ram, evolved in cold regions, is more resistant to the freezing process.