EFFECT OF SOYBEAN LECITHIN-BASED SEMEN EXTENDER ON FREEZABILITY AND FERTILITY OF RAHMANI RAM SPERMATOZOA

ABSTRACT
This experiment was designed to compare the protective action of soybean lecithin and egg
yolk on cryopreservation and fertility of ram spermatozoa. The semen ejaculates were collected
from three fertile rams, aged over 2.0 years and weighed round 65 kg, using artificial vagina. Two
extenders were prepared, 1st served as the control and contain15% egg yolk with Tris-citric acid
(TCEY).The second extender used 3.5 % soy lecithin to complete Tris-citric acid (TCSL). After
primary evaluation of ejaculates, the semen samples were extended at the rate of 1 semen: 4
dilutes. The packed diluted semen was used to perform three experiments with TCEY and TCSL
extenders. In the 1st experiment parameters such as progressive motility, viability and damaged
acrosome were assessed after equilibration period at 5°C for 3 hours. Concerning the 2nd
experiment, progressive motility, viability and abnormal acrosomes were evaluated after the
freezing-thawing process. In the 3rd experiment a fertility test with post-thawing TCEY and TCSL
extenders was performed. The results in the 1st experiment indicated that addition of 3.5% soylecithin
increased (P>0.05) progressive motility, viability and reduced abnormal acrosomes of
spermatozoa after equilibration period compared to 15% egg yolk extender. Although, TCEY and
TCSL extenders in experiment 2nd showed non-significant differences in post-thawing sperm
characteristics, the TCSL had improved post-thawing progressive motility, viability and rate of
damaged acrosome of ram spermatozoa. In the 3rd experiment a better pregnancy rate (P<0.05)
with TCSL (63.64 %) was observed compared to sperm preserved in TCEY (54.55 %). Based on
these results, we conclude that use of a chemically defined, soy-based medium improves long-term
motility and capacitation status of frozen–thawed ram' spermatozoa compared with
cryopreservation in a traditional protection (egg yolk) extender. Furthermore, the study clarify that
soybean lecithin could be able to increase proportions of viable frozen-thawed spermatozoa which
reflected positively on fertility rates.