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Genetic parameters for LM fatty acid composition were estimated in Scottish Blackface sheep, previously divergently selected for carcass lean content (LEAN and FAT lines). Furthermore, QTL were identified for the same fatty acids. Fatty acid phenotypic measurements were made on 350 male lambs, at approximately 8 mo of age, and 300 of these lambs were genotyped across candidate regions on chromosomes 1, 2, 3, 5, 14, 18, 20, and 21. Fatty acid composition measurements included in total 17 fatty acids of 3 categories: saturated, monounsaturated, and polyunsaturated. Total i.m. fat content was estimated as the sum of the fatty acids. The FAT line had a greater i.m. fat content and more oleic acid, but less linoleic acid (18:2 n-6) and docosapentaenoic acid (22:5 n-3) than did the LEAN line. Saturated fatty acids were moderately heritable, ranging from 0.19 to 0.29, and total SFA were highly heritable (0.90). Monounsaturated fatty acids were moderately to highly heritable, with cis-vaccenic acid (18:1 n-7) being the most heritable (0.67), and total MUFA were highly heritable (0.73). Polyunsaturated fatty acids were also moderately to highly heritable; arachidonic acid (20:4 n-6) and CLA were the most heritable, with values of 0.60 and 0.48, respectively. The total PUFA were moderately heritable (0.40). The QTL analyses were performed using regression interval mapping techniques. In total, 21 chromosome-wide QTL were detected in 6 out of 8 chromosomal regions. The chromosome-wide, significant QTL affected 3 SFA, 5 MUFA, and 13 PUFA. The most significant result was a QTL affecting linolenic acid (18:3 n-3) on chromosome 2. This QTL segregated in 2 of the 9 families and explained 37.6% of the phenotypic variance. Also, 10 significant QTL were identified on chromosome 21, where 8 out of 10 QTL were segregating in the same families and detected at the same position. The results of this study demonstrate that altering carcass fatness will simultaneously change i.m. fat content and oleic, linoleic, and docosapentaenoic acid content. The heritabilities of the fatty acids indicate opportunities for genetically altering most fatty acids. Moreover, this is the first report of detection of QTL directly affecting fatty acid composition in sheep.

This study investigated the effects of weaning and sex on various aspects of production and quality characteristics in 22 male and 18 female lambs of the Rasa Aragonesa local meat breed. Half the lambs were weaned (W) at 38 to 40 days and half were left unwearied (UW). Both groups were given ad libitum concentrates and cereal straw. Average farm weight was 22·1 kg at 78·3 days. Live-weight gain was significantly different between sexes but not between W and UW lambs. Dressing proportion was higher in UW lambs. Significant differences in fatness were found between W and UW lambs and between sex of lambs. Among the meat quality traits, W lambs had redder and UW lambs paler meat judged by colour a* and haem pigment concentration. No statistical differences were found in the other traits except flavour intensity, which was higher in UW (66·8) than in W (63·6) lambs on a 1 to 100 scale. All other eating quality aspects, in grilled m. longissimus lumborum slices, tended to be higher in UW lambs. The fatty acid composition of subcutaneous and intramuscular fat depots differed significantly (intramuscular fat was more unsaturated and polyunsaturated). There were also differences between W and UW lambs in subcutaneous fat (higher unsaturated in W lambs). However in intramuscular fat composition only differences in polyunsaturated fatty acids (higher in UW lambs), but not in total unsaturated or saturated, were observed. Tatty acids of less than C16 chain length were higher, in both fat depots, in UW lambs than in W lambs reflecting greater incorporation of milk fatty acids. Palatability characteristics were not closely associated with fatty acid composition except that flavour intensity was correlated with total saturated fatty acids. [ABSTRACT FROM PUBLISHER]