A crossbreeding experiment was performed for four years using four synthesized strains of chickens
involving Mandarah (MN), Matrouh (MT), Inshas (IN) and Silver Montazah (SM) to estimate direct additive
genetic effects, maternal effects, direct heterosis and maternal heterosis for body weight at hatch (BW0), 4
(BW4), 8 (BW8), 12 (BW12) and 16(BW16) weeks of age as well as daily weight gains during the age intervals
from hatch to 4 weeks (DG0-4), 4-8 weeks (DG4-8), 8-12 weeks (DG8-12) and 12 to 16 weeks (DG12-16). A
total number of 34 sires and 230 dams from MT strain and 32 sires and 194 dams from MN strain were used to
produce purebreds of MT and MN, two-way crossbreds (½MT½MN and ½MN½MT) and three-way crossbreds
(½SM¼MT¼MN and ½IN¼MN¼MT). Heritability estimates were ranged from 0.13 to 0.57. The ranges in
predicted breeding values (PBV) for body weights and daily gains in MN strain were slightly higher than in MT
strain and were slightly higher in ½MN½MT than in ½MT½MN. PBVs were slightly higher in (½IN¼MN¼MT)
than (½SM¼MT¼MN). The solutions of direct additive effects for body weights and daily gains were
significantly in favour of MT strain, while the solutions of maternal effects were significantly in favour of MN
strain. The percentages of direct and maternal heterosis were significant for all the studied traits and ranged
from 12.3 to 64.0% and from 6.5 to 21.8%, respectively. The contrasts of three-way crosses were significant and
superior in body weights and daily gains compared to two-way crosses |
