Substitution of Egg Yolk with Arabic Gum in Extenders Used for Ram Semen Cold Storage or Cryopreservation

Abstract

The current research was designed to compare the effects of substitution of egg yolk (EY) in ram extender with Arabic gum (AG) in different concentration in cooled or frozen semen collected by artificial vagina (AV) or electro-ejaculator (EE) in Noemi rams. Semen was collected 2 times per week for 6 weeks from 6 rams by EE method and after a rest period of 2 weeks, semen samples were collected by AV method. Tris extender either contained 15% EY (Control) or 3%, 5% or 7% AG (AG3, AG5 and AG7, respectively) were used as semen extenders. Spermatozoa were evaluated after cold storage (4 °C) or freezing/thawing in liquid nitrogen for sperm motility parameters: total motile spermatozoa (% TMS), rapid progressively motile sperm (% PRS), curvilinear velocity (VCL) μm/s, rectilinear velocity (VSL) μm/s, the average path velocity (VAP) μm/s, straightness index (% STR), linearity coefficient (% LIN), morphological defects and acrosome membrane integrity. Results showed that AV-collected sperm and diluted with AG or EY were more efficient in motility than EE. The values of VCL, VSL and VAP were higher in AG3 and AG5 and EY extenders for semen collected by AV compared to EE. After cold storage, AG3 gave better (P<0.01) results of LIN and STR either in spermatozoa collected by AV or EE. Significant differences in morphology defects were noted in semen collected by EE regardless of extenders used, however, AG supplementation enhance morphological defects in spermatozoa collected by AV (P<0.05). Post-freezing, Tris extender containing EY and AG5 in AV-collected spermatozoa had higher TMS, PRS, VCL, VSL and VAP compared to others. Sperm morphological defects were higher in AG7 extender in EE and EY extender in AV group. Plasma membrane integrity was significantly (P<0.05) higher in AG3 and AG5 extenders in AV-group compared to control and other groups. The acrosome membrane integrity in AV-semen groups was greater (P<0.05) than that of EE-semen group. It can be concluded that, Arabic gum is a good candidate to replace egg yolk in ram semen extender when added at a concentration of 3 or 5%. Although method of artificial vagina semen collection gave better results than electro-ejaculator. However, Arabic gum could be added to ram semen extender to enhance the electro-ejaculator-collected semen characteristics when added at a concentration of 5%