A total of 3005 and 2663 straight run broiler progeny of 44 and 50 sires each of two growth selected populations PB-1 and PB-2 maintained at PAU Ludhiana were used for the present investigation. The birds were raised on deep litter to six weeks of age and thereafter incidence of keel defects and Breast conformation score (BCS) were recorded on individual broiler by an expert team. A subjective score of 1 to 4 was given to BCS, 1 denoting a narrow and angular and 4 a round and well-developed breast. Likewise, the keel defects were also classified into three categories, Type-I represented normally developed keel without any apparent defect, Type-II-mildly twisted keel, Type-III-more pronounced twisted keep and Type-IV knobby keel whereby the anterior tip of the breast bone was prominent. Incidence of keel defects (KD) was lowest in BCS-4 category (1.72-2.41%), while the mediocre conformation had highest proportion of keel defects (7.12-17.31%). The association between keel defects and the BCS revealed that the two traits were negatively correlated (-0.22 to –0.48). The incidence of keel defects within each BCS was highest in BCS-1 and lowest in BCS-4 implying that broilers with better-developed breast portions had lesser incidence of keel defects. The correlation coefficients between the incidence of KD within each conformation and BCS were very high in both the sexes of the two populations (0.83 to 0.97). Very high correlations between the two sexes for the incidence of KD (0.96-0.98) indicated that the genes affecting the two traits might be the same in the two sexes.
Source : IPSACON-2005