| dc.description.abstract | Over several last decades increase in milk production of high yielding dairy cows is
accompanied by worsening of their reproductive results representing obvious and
direct consequence of one trait selection in cattle breeding. This problem attracts
much attention due to the fact that exploitation life of dairy cows is lowered to
that extent, that small number of female offspring is not sufficient to satisfy heard
turnover rate. As both reproduction and milk yield are of multifactorial nature, we
wish to point out once again complexity of this problem including some our
observations as well. Milk yield and reproduction are highly influenced by genetic
factors and adequate management. During early postpartum period, factors
affecting future fertility are body condition score, negative energy balance,
metabolic disorders, uterine and udder infections, lameness and appearance of
the first estrus postpartum. Also are important: estrus behavior, fertilization
failure, embryonic death and regular cycling. Embryonic death can be very early,
early and late and finally we can speak about neonatal or calf mortality. For
improving fertility we should reduce body condition score loss, treat uterine
infections, timely detect estrus and perform AI with high quality semen in the
optimal moment. Oocytes should be of high quality and an early increase of
progesterone P4 concentration followed by sufficient amount of the uterine milk
is needed. Embryo should grow quickly to produce enough interferon t providing
signal to cow that implantation has occurred, also preventing secretion of
luteolytic PG 2a. Our findings confirm that first AI, following calving, is often
performed in the moment when cows (many of them) are suffering from negative
energy balance, already having reduced chances for fertilization. As in the AI,
amount of highly immunosuppressive seminal plasma is significantly reduced and
semen extenders contain numerous new antigens, titers of the specific anti-spermantibodies of the Ig A class in the cervical mucus are increasing. These antibodies
can agglutinate and immobilize sperm cells additionally reducing chances for
fertilization. | en_US |
