The purpose of this graduation thesis was to find out what are the main reasons for too calving interval and deterioration of fertility at dairy cows. Breeders not intend enough attention to management and selection in their herds. To improve fertility, breeders should select animals for their longevity and feet & legs characteristics. With optimal nutrition and housing systems for dairy cows, breeders influence on optimal functioning of hormones, which are important for reproduction and fertility of cows. Due to growing herds and increasing work on their farms, breeders are paying too little attention to discovering animals in heat and they have too little time to observe the animals. That’s the reason that many of cows in heat are overlooked. It is also very important that we regularly perform the correction of hoof, since only healthy animals have no problems with locomotion and they can show signs of heat. During the summer, we have to assure that animals have suitable micro-climate conditions and with appropriate ventilation to avoid heat stress. Many mistakes in dairy herds are made during the drying-off period, as the consequences of these mistakes are reflected in the poor fertility of these cows in the next lactation. The feeding and animal care in the drying-off period is the basis for milk production, good fertility and animal health in the next lactation. Animals lose weight after calving, so they often fall into a negative energy balance. Due to improper nutrient supply before calving, animals after calving may fall into different health problems like ketosis, acidosis, milk fever, mastitis… With using different sensors to monitor activity, we can easier identify cows in heat in our herds. Fertility needs to be improved through different strategies, as breeders incur considerable losses and unnecessary costs at the expense of the poor fertility of their cows.