Characteristics of Lacha and Rasa Aragonesa lambs slaughtered at three live weights

A study was made of differences in the quality of meat from Lacha (L) and R asa Aragonesa (RA) lambs slaughtered at 12, 24, or 36 kg live weight. Lambs from both breeds were weaned at 25 to 57 d, approximately 11.5 to 18.5 kg live weight, and fed concentrate and barley straw until slaughter at 24 and 36 kg live weight. Hot carcass weight, cold carcass weight, conformation, color, firmness, and thickness of backfat and color of rectus abdominis mus cle were recorded on the carcass. Final pH (pH,), instrumental color (L*, a *, b*), myoglobin concentration, chemical composition, and water-holding ca pacity (WHC) of the longissimus muscle, shear force of the biceps femoris m uscle, and iodine values and fatty acid composition of the i.m. and s.c. fa t depots were determined. The percentage of fat in the longissimus muscle i ncreased with live weight, and values for RA lambs were higher than those f or L lambs. The WHC of meat from RA lambs was lower at 24 kg than at 12 or 36 kg slaughter weight. Live weight and breed had no effect on the shear fo rce of the biceps femoris muscle. There was an increase in myoglobin concen tration in the longissimus muscle with increased live weight in both breeds . The fatty acid content of s.c. and i.m. fat, which was not affected by br eed, declined with the increase in slaughter weight. The polyunsaturated fa tty acid content of the s.c. fat depot increased, whereas that of the i.m. fat depot decreased, with the increase in slaughter weight in both breeds. Subcutaneous fat had a higher content of heptadecanoic acid (17:0) than i.m . fat, and this increased with the increase in slaughter weight. In both de pots, there was an increase in oleic acid (18:1) at 12 kg in RA lambs and a t 24 kg in L lambs. In the s.c. fat depot, there was a progressive increase in linoleic acid (18:2) content with the increase in Live weight in both b reeds. There was a higher degree of unsaturation in the s.c. fat of RA lamb s than in that of L lambs, which was reflected in the iodine value.