Environment and Management II

S OF PAPERS 231 79 Relationships of egg and chick weight on the performance of progeny from standard and dwarf broiler dams. M. Tahir*1, H. Cervantes3, C. W. Farmer2, and G. M. Pesti2, 1Agricultural University, Peshawar, Khyber Pakhtunkhwa, Pakistan, 2University Georgia, Athens, 3Phibro Animal Health, Ridgefield Park, NJ. Eggs were collected from 2 commercial crosses (42 weeks of age) with the same male parent. One female parent was dwarf (dw-). Broiler progeny performance as function of egg and chick weights was investigated. Fertility (91.7 vs 94.7%) and hatchability (95.2 vs 96.3%) were similar for eggs from standard and dwarf dams, respectively. Egg weight (EW) contributed significantly to variation in body weight (BW). A female broiler hatched from a 63 g egg from a dwarf dam was predicted to weigh 3107.77 + 7.61(63) −37.42 −576.32 = 2973 g at 50 d. The coefficient for chick weight (CW) was positive but non-significant. However, in one model, both egg and chick weights were highly significant. The negative coefficient for CW in one model suggested that of the 2 broilers of the same EW, the one with the greater CW would have the smaller 50 d BW. Chick weight was a linear function of EW but the little improvement in R2 with the quadratic effect of EW indicated that the effect of egg or chick weight on broiler body weight at 35 or 50 d was best represented by a single linear function. Differences in BW due to EW increased with broiler age. The coefficients of egg and chick weights predicted that the differences in BW per g of egg were 1.43, 3.06, 6.24 and 7.61 g and per g of chick were 1.87, 3.99, 8.14 and 9.93 g, respectively, at 7, 21, 35, and 50 d. The coefficients relating BW to EW and CW increased by 0.1563 and 0.2092, respectively, per day of age for males from standard dams. Clearly both egg and chick weights are important for modeling or predicting market age broiler weight and economic returns. No significant differences were observed between 50 d body weight and hot carcass yields of broiler chicks from standard vs dwarf dams. These results compared with those from 1980s indicated that genetic selection has decreased the influence of EW on broiler growth and the present dwarf broiler breeder dams may produce progeny comparable in performance to the standard dams. However, the exact amount attributed to the dwarfing gene cannot be estimated from this study because of the different genetic backgrounds of these female parents.