DIFFERENTIAL EXPRESSION OF CERTAIN FERTILITY MARKER GENES IN YAK SEMEN AND THEIR ASSOCIATION WITH YAK EMBRYO PRODUCTION
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Date
2020-07
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College of Veterinary Science, Assam Agricultural University, Khanapara, Guwahati
Abstract
Six healthy yak bulls of 3-5 years age and twenty four healthy cyclic female yaks,
in their first to second lactation stage, aged 3 to 4.5 years, maintained at ICAR-NRC on
Yak, Dirang were used to study the effect of seasons and additive in semen qualities, the
expression pattern of certain fertility associated genes in yak semen, and their association
with semen characteristics and embryo production. A total of 216 ejaculates collected by
standard artificial vagina method were evaluated for volume, initial sperm motility,
sperm concentration, live sperm, sperm abnormality, HOST-reacted sperm, acrosomal
abnormality and intake acrosome in fresh semen in different seasons. Each ejaculates
were split into two equal parts for fresh and frozen semen study, and the fresh semen part
was divided into two parts for studying semen characteristics and mRNA gene
expression, while the frozen part was divided into two parts to study the effect of
additives in different stages of processing and freezing, and for mRNA gene expression
studies.
All the parameters for fresh semen characteristics varied significantly (P<0.01)
between seasons and between animals, while live sperm (%) varied significantly
(P<0.05) between seasons. The interaction between season and animals was found to be
non-significant except in live sperm (%) that varied significantly (P<0.05), and
acrosomal abnormality (%) and intake acrosome (%) that varied significantly (P<0.01).
The percentage of sperm motility, live sperm, HOST-reacted sperm and total
acrosomal changes of yak semen differed significantly (P<0.01) between additives and
between the seasons, but no difference was observed in their interaction. The total
acrosomal changes of yak semen showed interaction between additives and seasons after
equilibration and thawing during processing and freezing. Better quality of fresh yak
semen was obtained in the autumn season.
Freezing did not seemed to have any effect on YWHAZ gene expression but had
significantly negative effect on the expression of CATSPER2 gene during premonsoon,
and a positive influence on PRM1 gene expression in all the seasons. Autumn season
appeared to have no influence on the expression of YWHAZ gene, but had a positive and
negative influence on the expression of CATSPER2 and PRM1 gene, respectively.
Winter season had a positive influence on the expression of CATSPER2 and YWHAZ
genes, and a negative influence in the expression of PRM1 gene. All the three genes
showed highly significant positive correlation with most of the characteristics of fresh
semen viz. ejaculate volume, sperm motility, sperm concentration, live sperm count,
HOST-reacted sperm and intact acrosome, and negative correlation with sperm
abnormalities and total acrosomal changes in all the seasons.
Tweenty four female yaks were synchronized by ovsynch protocol and following
superovulatory treatment with Stimufol (@400μg and @200 μg per animal) and Folligon
(@1500 IU and @1000IU per animal) in two different doses, a hundred per cent oestrus
response was observed in all the groups. The oestrus response, duration of estrus,
number of CL and embryo recovered in yaks did not differ significantly between the
different treatment groups and animals, but differed significantly (P<0.01) between the
treatment and the onset of estrus.The highest number (3.50 ± 0.65) of excellent grade
embryos were recovered from the animals treated with Folligon @ 1500 IU per animal.
The progesterone concentrations differed significantly between treatment and between
different days of observation in all animals of the group. The minimum concentration of
progesterone of 0.19 ± 0.43 ng/ml on the day of induced oestrus increased to maximum
level of 25.11 ± 2.67 ng/ml on the day 7th of induced oestrus.