abstract
The aim of this study was to determine the synergistic effects of centrifuged egg yolk
(EY) and soybean lecithin on post-thaw Caspian horse sperm motility, morphological
abnormalities, and assessment of membrane integrity. The centrifuged EY (CEY) was
added at concentrations of 2% and 4% to a defined INRA plus 1.25% soybean lecithin
extender used to freeze Caspian horse semen. In this experiment, ejaculates collected
from each Caspian horse (n ¼ 4) were divided into three equal aliquots and diluted in
CEY 2% (INRA2), 4% (INRA4) supplemented, and without any CEY (INRA0) in INRA plus
1.25% soybean lecithin extender, respectively. Thereafter, samples were frozen and
thawed following a standard protocol. Sperm cryosurvival was evaluated in vitro by
microscopy assessments of post-thaw sperm motility (by means of computer-assisted
semen motility analysis [CASA]), acrosomal and other abnormalities (head, mid-pieces,
and tail) and plasma membrane integrity (evaluated by HOST). In Caspian stallion,
semen extended with INRA2 had significantly higher CASA motility and CASA
progressive motility than those extended with the rest of extenders after freezing and
thawing (P < .001). There was no significant difference in path velocity (VAP), VCL, and
ALH among three groups (P > .05). For straight line velocity (P < .01) and LIN
(P < .001), the highest values were obtained from the INRA4 group. The highest
percentages of acrosomal and other abnormalities were found in semen diluted in
INRA4 (P < .001). In the group frozen INRA2, the percentage of membrane integrity
was significantly higher than that of the other groups (P < .001). The use of CEY 2% in
combination with soybean lecithin significantly improved Caspian horse semen
freezability.