A 2-week (2,4) records of body weight (BW), body length (BL), keel length (KL), breast girth (BG), wing length (WL), wing span (WS), thigh circumference (TC), shank length (SL) and principal component of body size (PC1) were used to study repeatability of growth traits of 88 broiler chickens composed of 29 Arbor Acre, 29 Marshall and 30 Ross strains. Repeatability of PC1 was higher than repeatability of body weight in Arbor Acre (0.90±0.0058 vs 0.60±0.0179), Marshall (0.97±0.0005 vs

more »

... and Ross (0.97±0.0005 vs 0.55±0.0173), indicating that greater amount of genetic improvement in lifetime average body size can be achieved using PC1 as basis for selection. Repeatability of BL, KL, BG, WL, WS, TC and SL were high and ranged from 93±0.0009 to 98±0.0001, 0.90±0.0013 to 0.96±0.0002 and 0.90±0.0012 to 0.96±0.0002 in the respective strains. The expected relative genetic gain was high using 2 records for PC1 and the linear traits, pointing out that the two records were enough to adequately characterize the inherent transmission ability of the birds. Selection based on the repeatability of the traits using two records will result in lifetime improvement of body size and conformation of these strains. Based on the repeatability of PC1, Marshall and Ross have greater inherent transmission ability and should be selected in favour of Arbor Acre to improve overall body size in chickens.