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Title: Genetic evaluation of the reproductive performance of large white pigs selected for components of efficient lean growth rate
Author: Kerr, Joanna Clare
Awarding Body: University of Edinburgh
Current Institution: University of Edinburgh
Date of Award: 1995
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The reproductive performance of Large White pigs divergently selected for daily food intake (DFI), lean food conversion (LFC), lean growth rate on ad-libitum feeding (LGA), and lean growth rate on restricted feeding (LGS) was investigated in a series of four studies. Correlated responses to selection in litter traits and the genetic and phenotypic relationships between performance test and reproduction traits were estimated after five generations of selection. The effects of the alternative selection strategies on gilt liveweight and backfat depth measured at mating, farrowing and weaning and food intake during lactation were examined after seven generations to selection. Responses in litter size and weight at birth and weaning were lower with selection for low DFI and high LFC than with selection for high DFI or low LFC. The average response in litter size at birth for the DFI and LFC selection groups was 1.5 pigs/litter. Responses in litter weights were a result of selection line differences in both litter sizes and piglet weights. The relationships between litter size, litter weights and piglet weights at birth and weaning were essentially linear. For ad-libitum fed pigs, genetic correlations between litter weights at birth and weaning with daily food intake and with growth rate on test were positive, but correlations with backfat depths were not significantly different from zero. For restricted fed pigs, litter birth weight was positively genetically correlated with growth rate and negatively correlated with backfat depth. Between selection line variation in backfat depth enabled detection of a non-linear relationship between predicted breeding values for litter weight at birth with predicted breeding values for average backfat depth of farrowing gilts performance tested on ad-libitum feeding. At the start of the mating period, gilts selected for high DFI, LGA or LGS had similar liveweights, but different backfat depths, while the low DFI, LGA and LGS lines had different liveweights but similar backfat depths.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available