Abstract :
The aim of this experiment was to study the growth performance of both ram and ewe
lambs, and the carcass characteristics of ram lambs of five genotypes: Awassi (A), F1
Charollais–Awassi (CA), F1 Romanov–Awassi (RA), B1 Awassi–(Charollais×Awassi) (ACA)
and B1 Awassi–(Romanov×Awassi) (ARA). One-hundred lambs (50 females and 50 males)
were separated into 10 groups according to sex and genotype from weaning until the end
of the experiment. Birth and weaning weights were recorded for all animals; live weight
was recorded for all animals on bi-weekly intervals between 2 and 8 months of age. At 8
months of age, 6 ram lambs from each genotype (a total of 30 ram lambs) were randomly
chosen for slaughter. Birth weights were similar while weaning weights differed among
the five genotypes being greater for the CA. Post-weaning live weights differed among
genotypes and according to lamb’s sex (P < 0.01). Genotype and lamb sex had significant
effects on the total weight gain and average daily gain (ADG) from birth till the end of the
experiment. The CA lambs outperformed other genotypes while ram lambs had better performance
than ewe lambs. The greatest ADG for all genotypes occurred during the period
from weaning to 5 months of age (fattening period). At slaughter, final live weight was
found to be significantly affected by genotype; the greatest weight was recorded for CA
genotype (62.5±4.0 kg). Slaughter weight and hot and cold carcass weights differed significantly
among the five genotypes with Awassi having the lightest weights. Dressing-out
percentage was also affected by genotype with CA lambs having the greatest value. Awassi
had lower eye muscle depth, the shorter carcass (P < 0.001), least fat tissue depth, lowest
linear measurements and the greatest fat tail percentage compared with the remaining
genotypes. Shoulder and rack percentages differed among the genotypes with Awassi having
the lowest values. In the dissected leg cut, muscle to bone ratio differed among the
genotypes with CA having the highest ratio. Awassi lamb meat had lower (P < 0.05) dry
matter and crude fat (on as wet basis) percentages than the other genotypes. Results of
this study indicate that crossbreeding Awassi with exotic breeds improves growth rate and
meat production.
