Correlated Responses of Various Body Measurements in Swine Selected for High and Low Fatness

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Abstract
DATA on four body measurements, i.e., length from ear to tail, height at shoulders, width at shoulders and circumference at chest were examined for correlated responses to selection for high and low backfat thickness in two lines of Durocs and two lines of Yorkshires. Included were comparisons of the selected lines with their respective unselected controls based on data collected through 12 generations in the Duroc lines and 10 in the Yorkshire lines. In Durocs, length showed a divergence of about 49% of that of backfat thickness between the high and low lines) while circumference, width and height gave values of about 45, 18 and 16%, respectively. The corresponding divergences shown by the same four traits between the high and low Yorkshire lines were 20, 25, 14 and 36%, respectively. The signs of the genetic correlations obtained between the various body measures and backfat thickness from offspring-mid-parent covariances all agreed with those of the correlations based on correlated selection responses. Also, the magnitude of the two sets of correlations agreed reasonably well for the most part. The results suggest that in both Durocs and Yorkshires length and height are negatively correlated genetically and that width and circumference are positively correlated genetically with backfat thickness. Only for height in Yorkshires and for circumference in both Durocs and Yorkshires did the results suggest an asymmetry in correlated responses. Copyright © 1972. American Society of Animal Science. Copyright 1972 by American Society of Animal Science.

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