1FEED INTAKE BEHAVIOR AND IMPLICATIONS FOR ENERGY UTILIZATION

The study of feed intake has been greatly facilitated by the recent development of computerized systems that monitor the feed intake of individual animals within a group. Such equipment was originally designed for use by breeding stock supply organizations in the performance testing of pigs in group situations. The majority of selection programs for pigs place considerable emphasis on feed efficiency because of its impact on production costs. Historically, genetic improvement in feed efficiency was achieved as a correlated genetic change resulting from selection for growth rate and carcass lean content for animals tested in groups, where individual feed intakes could not be measured. Alternatively, pigs were penned and fed individually to obtain feed intake data, a procedure that is expensive in terms of both labor and facility costs. In addition, animals that are genetically superior when penned as individuals may not perform the best in group-housed situations i.e. under commercial conditions. Studies that have compared the growth and carcass characteristics of boars that have been individually fed during the performance test with the performance of their progeny under commercial group-housed conditions. These have generally shown moderate to low correlations between performance in the two environments. This phenomenon is termed a genotype x environment interaction and suggests that different genes may be involved in controlling growt