[Progress on breeding for best-hybridized crossing of meat rabbits]

Best-hybridized crossing should ideally result in optimal exploitation of heterosis of lines and capitalize on expressed heterosis. Rabbit breeding is heading in the direction of breeding for best-hybridized crossing of meat rabbits. Most special sire lines are selected for post-weaning average daily gain and marketing weight. Post-weaning growth has a negative and favorable genetic correlation with the feed conversion ratio, which is used in indirect selection for feed conversion ratio. The most common selection criteria for special maternal lines are related to litter size at birth or at weaning. Since the heritability of most reproductive traits is low, we must collect as many individual and relative records as possible in the genetic evaluation of rabbits. The BLUP procedure under an animal repeatability model is the most common procedure used for evaluation of animals in selection programs for special lines of meat rabbits. Direct selection for litter size is less efficient than selection for post-weaning growth, but the estimation of heterosis is generally higher for litter size than that for the post-weaning growth. Evaluation of heterosis could be performed by estimating crossbreeding parameters in the cross or comparing contemporary productivity among purebreds and crossbreds. Here, we reviewed breeding of special lines, exploitation of heterosis of crossbreds, and establishment of crossbreeding system of hybrid meat rabbits and summarized the methodologies of breeding special lines, criteria in selection programs, and the result of heterosis estimates.