Multiple Assignment Tester Animals for Pasture‐Animal Systems1

Different forages or management practices are often evaluated as separate entities in conventional grazing trials. A more meaningful approach is to evaluate “pasture systems” for season‐long grazing, whereby separate pastures of different forages or managements comprise a pasture system, and each component is grazed at different periods during the season. The purpose of this paper is to stress the need for the evaluation of different forages or management practices within the framework of a total system and to suggest two practical experimental designs for pasture‐animal system experiments. Two types of pasture systems using multiple assignment testers are proposed: 1) systems with separate pastures and 2) systems with common pastures. With multiple assignment testers and common pastures, several pasture systems may be compared simultaneously, but require fewer pastures per replication. For example, only 6 pastures are needed for a 3 ✕3 system trial with common pasture, as compared to 18 pastures per replication for system trials with separate pastures. Animal and pasture production may be compiled for the total system and for each component of the system. Multiple assignment tester animals are defined as tester animals assigned to graze two or more components comprising a pasture system. In evaluation of the concept of pasture systems, experimental errors for measuring beef cattle gain per hectare and average daily gain per animal were nearly the same for grazing trials analyzed as a conventional trial and as a system trial with common pastures. The season‐long pasture system approach in grazing research provides the cattle producer with more realistic information on which to plan his pasture program.