A one-year project grant to Practical Farmers of Iowa to research livestock gastrointestinal parasite management resulted in a five-year series of experiments during which attention shifted from commercial botanical mixtures to single-ingredient botanical materials. The end of this period sees renewed interest in the role of management, as results of natural anthelmintics have been variable at best and largely disappointing. Our research results have also pointed to difficulties of collecting reliable data from these on-farm trials. The scarcity of available pens was anticipated and addressed through use of completely randomized design (CRD). However, in our experience the number of animals per pen needed to be much larger, or trials needed replication over time. Making sure that fecal samples and weights can be identified with individual animals is especially important when there are a limited number of animals in each treatment group.
