[Parasitic infections and herd fertility. An overview]

The negative impact of a parasitic infection not only affects the weight gain of the replacement heifer, but also her reproductive performance and hence the productivity of a cow-calf herd. A parasitic infection in the period between weaning and first service can put at risk the continuous weight gain essential for early reproductive maturity at 14-15 months. If, as a herd measurement, the so-called "critical minimum bodyweight" is not achieved by the timing set in the insemination or service plan, negative economic effects result, in the form of prolonged service periods and longer calving patterns. An effective parasite control plan in this critical time frame results in securing a high level of fertility. Such a parasite control programme should be carried out as a strategic measure, taking into account the age of the animal (susceptibility) and the natural risk of infection (pasture contamination). The treatment at the end of the grazing period at the time of housing is of particular importance.