Selection index alternatives for increased marketing body weight with minimum concomitant reduction in body bone percentagerecourse to tissue dissection on Japanese quail
Abstract. Live body weight, shank length, keel length and carcass dissection data taken at 6 weeks of age were available on 103 quails from 33 sires. In a principal factor analysis, the first varimax rotated factor explaining 46.1% of the total Variation, revealed that body weight had negative loading and all bone percentages positive. The implied contrast was confirmed by the finding that body weight (h,sup>2 = 0.61) was genetically correlated negatively with weight of total bone relative to body weight (−0.23) and to carcass weight (−0.58). Noticeably, shank length (SL) had large positive genetic correlation with body weight (0.90) and practically independent relationship with body bone percentage (−0.04).
Selection indexes for meat production capacity were construeted. The breeding goal was defined as body weight (BW) and body bone percentage (BBP). The descending order ofthe unrestricted indexes with respect to the correlation between the index and genetic worth was: the füll index utilising body weight, shank length and keel length (0.95), indexes based on body weight and one length measurement (0.86), body weight alone (0.78). The accuracy was reduced by 17–35% upon restraining changes in BBP to zero. This study indicated that an index of considerable accuracy and remarkable usefulness would be I3 = 4.56 BW + 244.87 SL. Use of this index should result in developing birds with higher body weight and more advantageous carcass attributes than selecting for body weight alone (L) or on the restricted füll index (II(BBP)). Such three indexes were most efficient in limiting reduction in BBP.
