Allometric study on carcass tissues from purebred Santa Ines lambs or crossbred with Texel, Ile de France and Bergamacia

This study was conducted using 103 male and female lambs from the following genetic groups: Santa Ines (SS) purebred and Santa Ines x Texel (TS), Santa Ines x Ile de France (FS), and Santa Ines x Bergamacia (BS) crossbred. The animals were slaughtered at the following body weights: 15, 25, 35 or 45 kg. After slaughter and cooling of the carcasses, the following cuts were made: neck, rib/flank, short ribs, loin, blade, and hind limb. The composition in muscle, bone and fat of cuts and 1/2 carcass were evaluated. The alometric growth of each tissue of the loin, shoulder and leg in relation to the cut weight, and of each tissue of the 1/2 carcass in relation to the cold carcass weight, was measured. The allometric growth of muscles in the 1/2 carcass, for BS males and FS and BS females, was early (b<1). The alometric growth of the bone in the cuts and 1/2 carcass was early (b<1), except for shoulder bone in SS, TS and BS males, and TS females; and leg bone in BS males, with isogonic allometric growth (b=1). The development of fat in the cuts, and 1/2 carcass was late (b>1), except shoulder fat in BS males, with isogonic growth (b=1). The growth rate of shoulder muscles in SS and FS males, SS and TS females was isogonic (b=1); for TS and BS males, FS and BS females, it was early (b<1). The muscle development in the loin from SS, FS and BS males, and females FS, was isogonic (b=1); for TS males and SS, TS and BS females, it was negative heterogonic (b<1). The allometric growth of the muscle in the loin from SS, TS and FS, and SS and TS females, was isogonic (b=1); and for BS males and TS and BS females, it was negative heterogonic (b<1).