Have New Feeding Technologies Revolutionized the Way We Design Grazing Experiments?

New technologies have enabled autonomous measurement of intake and feeding behavior of pen-fed animals and this has piqued interest in utilizing similar technologies in grazing experiments. Various feeding systems are currently available, but individual supplementation and feeding experiments have been conducted for years using individual feeding stanchions, which are the lowest level of technology for measuring supplement intake. These experiments are laborious as they require animals to be trained and acclimated, gathered at each feeding, and sorted into individual stalls for supplementation--thereby disrupting the animals grazing activities. In the mid-1980s Calan Gate systems (American Calan; Northwood, NH) became popular in pasture supplementation experiments, but still have many of the same disadvantages. Newer, more automated systems, reduce labor and possibly have less disruption of the animal's grazing behavior, but are reliant on the animal's willingness to use the system and ability to access it when more dominant peers are present. Individuals also do not always follow the "averages"-based rules we often hold true and behave differently in groups. Recent research with automatic feeders show steers consumed average of 60% of the potential supplement with supplement intake CVs of 50 to 100%. These technologies lead many to question the paradigm of experimental units in experimental designs. The experimental unit is defined as the smallest independently assigned unit to which the treatment is applied. This definition of experimental unit is somewhat limiting when taken to the extreme, but still applies well for experiments utilizing individual animal feeding, regardless of the level of technology involved. In many cases where the aforementioned technologies are used, the individual animal can be both the observational and experimental unit. This symposia presentation will discuss attributes of different feeding options and the implications on study design, experimental power, and the designated experimental unit. [ABSTRACT FROM AUTHOR]