CORRELATED RESPONSE IN CARCASS TRAITS WHEN USING SELECTION INDEXES INVOLVING MARKETING BODY WEIGHT AND DAILY GAIN IN NEW ZEALAND WHITE RABBITS

Abstract

Estimates of genetic and phenotypic parameters for live body and carcass traits on 121 New Zealand White rabbits, progeny of unrelated 13 bucks and 56 does were calculated and used to construct ten selection indexes. Traits in the aggregate genotype were marketing body weight (at 90 days) and daily gain from weaning to marketing. The index traits were body weight (at weaning and at marketing and daily gain between them) and body linear measurements (abdominal girth, body length and ear length). It is more efficient to use body weight traits indexes than body linear measurements indexes (rTI = 0.87 to 0.92 vs. 0.20 to 0.85, respectively) in predicting the true breeding value. Use of the index I2 = -0.82 weaning weight + 36.9 daily gain + 0.92 marketing weight (having rTI = 0.92) would be recommended to optimize selection for the given aggregate genotype and should result in rabbits characterized with heavier marketing weight (+153 g), faster daily gain (+2.3 g), better muscle to bone ratio (+0.2 unit) and enhancement of boneless percentage (+0.4 unit). However, genetic gain in marketing body weight and daily gain would be coupled with decrease in weaning weight (-19 g) and fatless side percentage (-0.4 unit) along with its percentage components of muscle (-0.4 unit) and bone (-0.4 unit). In the absence of growth records, the index I10 = +85.0 abdominal girth -72.1 ear length - 17.5 body length would be recommended.