The Egyptian Poultry Science AssociationEgyptian Poultry Science Journal1110-562338420181226SELECTION INDICES FOR IMPROVING BODY WEIGHT IN GABALI RABBITS.111511262290410.21608/epsj.2018.22904ENAmira SolimanEl-Deghadi*Anim. Prod. Res. Inst., Agric. Res. Center, Minis. of Agric., Dokki, Cairo, Egypt.Journal Article20181009Selection indices were constructed for improving body weight in Gabali rabbits, utilizing records of 515 progenies born from 29 does and 8 sires for four consecutive years. The statistical analysis was carried out using a multi trait animal model to estimate additive, common-litter and residual effects' variances. The adopted model included fixed (the effects of season, parity and litter size at birth) and random effects (additive genetic and common-litter effects) for post-weaning growth traits. Means of body weights of Gabali rabbits ranged from 604.4 g at 4 weeks of age to 2019.9 g at 12 weeks of age. Estimates of h<sup>2</sup> were 0.06, 0.18, 0.26, 0.11 and 0.10 for individual body weight at 4<sup>th</sup>, 6<sup>th</sup>, 8<sup>th</sup>, 10<sup>th</sup>, and 12<sup>th</sup> weeks of age, respectively. The estimate of common-litter effects (c<sup>2</sup>) for body weight at weaning was higher compared with other ages. Estimates of r<sub>G</sub> were high and positive for all possible/attained genetic correlations between body weights at various ages (ranged from 0.37 to 0.91). Selection indices were constructed incorporating the Gabali rabbits body weights at five different ages; body weight at 4<sup>th</sup> (X1), 6<sup>th</sup> (X2), 8<sup>th</sup> (X3), 10<sup>th</sup> (X4) and 12<sup>th</sup> (X5) weeks of age; respectively. In all indices the values of b's for individual traits varied from one index to another and were even, low, moderate to high plus negative in some and positive in other indices. On the basis of relative efficiency of the indices (RIH), the following four indices were recommended for sake of maximizing genetic response to selection.
<span style="text-decoration: underline;">Index no.</span>
<span style="text-decoration: underline;">Values of b</span>
<span style="text-decoration: underline;">RIH</span>
I14
- 0.5195 X2 + 0.6460 X3
0.633
I9
0.8293 X3 - 0.7570 X4 + 0.2950 X5
0.597
I11
- 0.1036 X1 + 0.2854 X3
0.504
I17
0.4562 X3 - 0.1689 X4
0.496
Expected genetic gain changes in each trait varied a lot from one index to the other. Yet, though RIH in some of the indices were found negative while positive in the others in the best indices, expected genetic changes of various traits were all positive. Standard deviation the aggregate of the genotypic (σ <sub>H</sub>) estimates were moderate or high and the heritability values for I14, I9, I11 and I7 indices were 0.21, 0.29, 0.15 and 0.25 respectively,https://epsj.journals.ekb.eg/article_22904_6d4de1ec4c49151661fa81526e7bd8c8.pdf