Abstract :
Genotype effects on lamb carcass traits were investigated in a 4-year study aimed at assessing
potential benefits from introducing meat breeds into the wool-oriented extensive sheep
systems of northeastern Patagonia, Argentina. Five ram [Corriedale: CO; Border Leicester:
BL; Île de France: IF; Texel: TX; and synthetic CRIII (25% Merino, 37.5% IF, 37.5% TX)] and
5 dam (CO; synthetic CRIII; BLCO: BL ×CO; IFCO: IF × CO; and TXCO: TX × CO) genotypes
were represented in the study. Data were collected from 436 male lambs of 9 genotypes
(CO ×CO, BL × CO, IF × CO, TX × CO, CRIII × CO, CRIII × BLCO, CRIII × IFCO, CRIII × TXCO, and
CRIII × CRIII). Hot carcass weights and dressing yields were determined after slaughtering.
Carcasses were given conformation and subcutaneous fat scores using the EUROP system
[scale varying from E (best) to P (poorest) for conformation, and from 1 (lean) to 5
(overfat) for subcutaneous fat]. Linear measurements of carcass length and width were
recorded and carcass compactness indices were calculated from those. Purebred CO acted
as a standard for comparisons. On a constant liveweight basis, genotypes CRIII ×IFCO and
CRIII × CRIII presented higher (P < 0.05) carcass weight and dressing yield than CO × CO and
BL × CO. Crossbred and synthetic genotypes showed higher (P < 0.05) carcass width than
CO × CO. With the exception of BL × CO the remaining genotypes showed higher (P < 0.05)
carcass width/length ratio than CO × CO. The probability that carcasses of crossbred and
synthetic lambs presented better conformation than CO × CO was higher than 84%. Carcasses
of CRIII × IFCO lambs were given the best conformation scores. The probability
that BL × CO carcasses presented higher subcutaneous fat than the remaining genotypes
exceeded 79%. Our results indicate significant improvements in carcass conformation arising
from crossing. Sheep farmers in extensive systems could take advantage of the higher
fatness of BL crossbred lambs to produce light carcasses with adequate fat cover, a crucial
industry requirement. Terminal crossbreeding with Île de France, Texel, and CRIII rams
could be implemented to improve carcass conformation thus matching market demand for
heavy carcasses with limited fat content. Second cross schemes did not improve carcass
commercial traits over the best terminal cross or the synthetic CRIII breed.
