The effect of dietary supplementation of organic selenium and chromium on Mehraban ram semen quality during liquid storage at 4 °C

Some previous researches have shown that dietary supplementation with some vitamins and trace elements can increase the ability of animals semen preservation during liquid storage or freezing. Therefore, the aim of this study was to investigate the effect of dietary supplementation of organic selenium and chromium on ram semen quality during liquid storage at 4 °C.

Numbers of 16 Mehraban rams, with ages ranging from 2-4 years and 69.75±10.44 kg average body weight, were divided into four groups of four and were fed by a basal diet consist of 70% forage and 30% concentrate. The experimental design was 2×2×4 factorial experiment based on randomized complete block design. The experiment lasted for 60 days. In this experiment, three factors were including selenium at two levels (0 and 600 µg/day/ram selenium as yeast-selenium), chromium at 2 levels (0 and 1000 µg/day/ram chromium as chromium-methionin) and time at 4 levels (0, 24, 48 and 72 hours after storage). Chromium was fed to rams using edible capsule shells and also selenium by drencher after dissolving in distilled water. In the last three weeks of the experiment, semen samples were collected 3 times. Semen samples after collection was diluted with tirs-egg yolk base extender and stored at 4°C for 72 h. Sperm cells viability, membrane integrity, abnormal morphology, total motility and progressive motility and some motion parameters is detected by computer-assisted sperm analysis at 0, 24, 48 and 72 hours after storage.

The effects of chromium, time and their interaction and also selenium × chromium interaction, selenium × chromium × time interaction were significant for sperm viability and membrane integrity (p < 0.05). The effect of selenium and selenium × chromium interaction was not significant for viability (p>0.05) but, the effect of chromium, selenium and time and also their interaction for membrane integrity was significant (p < 0.05). The viability reduced over time significantly (p < 0.05) and sperm viability in rams receiving the diet contained 1000 μg chromium, was higher than diet without chromium after storage at 4°C for 48 and 72 hours (p < 0.05). In addition, sperm viability in rams receiving the diet contained 600 μg selenium was higher than diet without selenium after storage at 4°C for 48 hours (p < 0.05). Adding 1000 μg chromium to diet containing 600 μg selenium, increased significantly sperm viability after storage at 4°C for 48 and 72 hours (p < 0.05). The membrane integrity reduced over time significantly (p < 0.05) and sperm membrane integrity in rams receiving the diet contained 1000 μg chromium was higher than other groups after storage at 4°C for 24 and 48 hours (p < 0.05). The effect of selenium and chromium and also their interaction was not significant for computer detected parameters (p < 0.05). Interaction of selenium and chromium for abnormal morphology was significant (p < 0.05) but the effects of chromium, selenium, time and their interaction was not significant (p>0.05). Total motility, velocity in curvilinear line, velocity in straight line, velocity in average path decreased over time during semen storage at 4°C (p < 0.05) and diet supplementation of selenium and chromium did not change these parameters (p>0.05). Progressive motility, abnormal morphology and straightness did not affected by time, selenium and chromum.

Generally, dietary supplementation of organic selenium and chromium in rams leads to increased sperm viability and membrane integrity during chilled liquid storage. Dietary supplementation of selenium and chromium did not change computer detected parameters during semen storage at 4°C. In general, the use of organic selenium and chromium in the diet of rams may increase the ability of sperm storage for artificial insemination.