Document Type : Original Article
Authors
1
Animal Production Department, Faculty of Agriculture, Ain Shams University, Shoubra El-Kheima, 11241 Cairo Egypt
2
Animal Production Department, Faculty of Agriculture, Ain Shams University, Shoubra El-Kheima, 11241 Cairo, Egypt.
Abstract
The aim of this work is to investigate the consequences of selection for post-weaning growth performance on carcass composition and carcass meatiness traits. Seven selection indices were applied using estimates of genetic and phenotypic parameters on 218 New Zealand White (NZW) rabbits, progeny of 24 bucks and 93 does, via a multi-trait animal model. Weaning weight (WW), Slaughter weight (SW) and daily gain between them (DG) were used as sources of information. The breeding objective was to enhance the profitability of NZW rabbit breeders by maximizing WW, SW, and DG. The carcass composition was represented as the percentage of dissected side weight deposited as muscle (MP), Fat (FP), and bone (BP), while carcass meatiness traits were represented as carcass weight (CW), dressing percentage (DP), muscle: bone ratio (MB), and muscle: fat ratio (MF). The heritability estimates (h2) were 0.69, 0.44 and 0.54 for WW, SW and DG, respectively. Carcass composition traits showed moderate estimates of h2 for MP (0.31) and FP (0.35) and a very high value for BP (0.91). The h2-values for carcass meatiness traits were 0.42, 0.43, 0.89, and 0.75 for CW, DP, MB, and MF, respectively. The full index (I1): I1 = 6.39 WW - 1.85 SW + 150.92 DG had the highest correlation with the aggregate genotype (rTI = 0.81), followed by the best reduced index involving WW and DG (rTI = 0.79): I3 = 4.21 WW + 71.74 DG.
However, the single trait selection index based on WW alone (I5 = 4.46 WW) is expected to be as efficient as the best reduced index (rTI = 0.76).
At each round of selection with the intensity of selection = 1.0, applying of I1, I3 and I5 are expected to result in developing NZW rabbits with better post-weaning growth performance in terms of heavier body weight at weaning (ranged from 112.93 to 121.35 gm) and slaughtering (ranged from 124.70 to 135.52 gm) with faster daily gain (ranged from 0.32 to 0.78 gm/day). This enhancement in post-weaning growth performance is expected to consequence in an increase in MP (ranged from 0.67 to 0.82 unit) and FP (ranged from 0.31 to 0.59 unit) and reduction in BP (ranged from -0.43 to -0.31 unit). Carcass meatiness traits are expected to be more favorable in terms of higher DP (ranged from 0.14 to 0.38 unit) and MB ratio (ranged from 0.28 to 0.36 unit) and less favorable in terms of MF (ranged from -0.23 to -1.60 unit).
Conclusively, the results obtained in the present study suggested that selection based on the single trait index I5 including the weaning weight trait would be recommended to improve the given aggregate genotype traits for being an early, single, and easy-to-measure.
Keywords
)
View on SCiNiTO