The objective of this study was to investigate the relative importance of social effects on response for total genetic value from selection of boars for ADG. Records of 9,720 boars from dam lines (1 and 2) and sire lines (3 and 4) from Pig Improvement Company (PIC, Franklin, KY) were analyzed. Data were from 4 test farms over a 4-yr period (2000 to 2003). It was determined that further study of the effects of social interactions in different environments is needed to determine situations in which effectiveness of selection for total genetic value can be improved by incorporating social effects in models and indexes. An anonymous reviewer has suggested that this model for direct and social effects not be used in the future for several reasons. One reason is the complete confounding of fixed pen effects and environmental social effects and near confounding when pens are modeled as random effects. In this study pen effects were not included in the model. Another reason is one the authors and others have informally discussed; with many
pigs in a pen, some pigs may never interact with other pigs.

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