O plodnosti i mlečnosti krava - opet

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.