Influence of fresh alfalfa supplementation on fat skatole and indole concentration and chop odour and flavour in lambs grazing a cocksfoot pasture

Change in fat skatole and indole content in lambs switched from a concentrate-based diet indoors to alfalfa grazing for various durations before slaughter

Meat from lambs fattened on alfalfa is at risk of excessive pastoral flavours due to high levels of in-fat volatile indolic compounds (especially, skatole). Skatole has also been identified as a potential marker of interest for authenticating pasture-fed lamb meat. Here, we investigated the change in skatole and indole concentrations in kidney fat from lambs switched from an indoor-fed concentrate based diet to outdoor alfalfa grazing for various durations (0, 21, 42, 63 days) before slaughter. The study used a total of 219 lambs over 3 consecutive years. Kidney-fat skatole and indole concentrations increased from as early as 21 days on alfalfa, and then reached a plateau. Similarly, the proportion of lambs that had a kidney fat-skatole concentration above 0.15 μg/g liquid fat, a value that has been established as a sensory rejection threshold for pork, increased significantly from as early as 21 days on alfalfa and then reached a plateau. This value was reached or exceeded in a significant proportion of lambs fattened on alfalfa pastures (45.1%). However, skatole was not detected in kidney fat from 20 out of 164 alfalfa-fattened lambs (i.e., 12.2%) but was detected in 15 out of 55 concentrate-fed lambs (i.e., 27.3%). We thus conclude that while skatole content in kidney fat can inform on dietary changes made shortly before slaughter, it does not have the discrimination power needed to reliably authenticate pasture-fed lamb meat, let alone duration of finishing on pasture.

Transcriptome analysis reveals candidate genes of the synthesis of branched-chain fatty acids related to mutton flavor in the lamb liver using Allium Mongolicum Regel extract

The objective of this study was to identify candidate genes via which Allium mongolicum Regel ethanol extract (AME) affects the synthesis of branched-chain fatty acids (BCFAs) related to mutton flavor by transcriptome analysis in the lamb liver. Thirty male Small-tailed Han sheep (3 mo old; 33.6 ± 1.2 kg) were randomly divided into two groups and fed for 75 d with a basal diet containing no AME (CON, control group) or 2.8 g·lamb⁻¹·d⁻¹ AME (AME group). Twelve sheep, CON (n = 6) and AME (n = 6), were selected for slaughter at the end of the trial period, and liver samples were subsequently collected. There was no difference in 4-ethyloctanoic acid content among treatments. The 4-methyloctanoic acid and 4-methylnonanoic acid levels were significantly lower in the AME group than in the CON group (P < 0.05). Furthermore, 461 differentially expressed genes (DEGs) were identified between the CON and AME groups, of which 182 were upregulated and 279 were downregulated in the AME group. The DEGs were enriched in three pathways, namely, glutathione metabolism, ECM–receptor interaction, and steroid hormone biosynthesis, as determined by the Kyoto Encyclopedia of Genes and Genomes pathway analysis. Finally, CYP2B6, ACOT12, THEM4, ACSF2, LPIN1, and ADCY4 were identified as candidate genes that might be involved in regulating the BCFAs synthesis in the sheep liver.

Review: Factors affecting sheep carcass and meat quality attributes

Sheep meat comes from a wide variety of farming systems utilising outdoor extensive to indoor intensive with animals of various ages at slaughter. In Europe, slaughter may occur from 4 weeks of age in suckling light lambs to adult ages. More than any other animal species used for meat production, there are strong country-specific preferences for sheep meat quality linked to production system characteristics such as dairy or grassland-based systems. This article critically reviews the current state of knowledge on factors affecting sheep carcass and meat quality. Quality has been broken down into six core attributes: commercial, organoleptic, nutritional, technological, safety and image, the latter covering aspects of ethics, culture and environment associated with the way the meat is produced and its origin, which are particularly valued in the many quality labels in Europe. The quality of meat is built but can also deteriorate along the continuum from the conception of the animal to the consumer. Our review pinpoints critical periods, such as the gestation and the preslaughter and slaughter periods, and key factors, such as the animal diet, via its direct effect on the fatty acid profile, the antioxidant and volatile content, and indirect effects mediated via the age of the animal. It also pinpoints methodological difficulties in predicting organoleptic attributes, particularly odour and flavour. Potential antagonisms between different dimensions of quality are highlighted. For example, pasture-feeding has positive effects on the image and nutritional attributes (through its effect on the fatty acid profile of meat lipids), but it increases the risk of off-odours and off-flavours for sensitive consumersand the variability in meat quality linked to variability of animal age at slaughter. The orientation towards more agro-ecological, low-input farming systems may therefore present benefits for the image and nutritional properties of the meat, but also risks for the commercial (insufficient carcass fatness, feed deficiencies at key periods of the production cycle, irregularity in supply), organoleptic (stronger flavour and darker colour of the meat) and variability of sheep carcass and meat quality. Furthermore, the genetic selection for lean meat yield has been effective in producing carcasses that yield more meat, but at a penalty to the intramuscular fat content and eating quality of the meat, and making it more difficult to finish lambs on grass. Various tools to assess and predict quality are in development to better consider the various dimensions of quality in consumer information, payment to farmers and genetic selection.

The quality and mineral composition of the longissimus lumborum and semimembranosus muscles from lambs fed perennial or annual wheat forage with or without lucerne

This study compared the effect of a novel perennial wheat forage and a conventional annual wheat forage, fed to lambs with or without lucerne, on the quality and mineral profile of the longissimus lumborum and semimembranosus muscles. This involved 48 Poll Dorset × Merino ewe lambs, 12 per treatment, managed for 28 days within individual pens. Consumer sensory panel scores showed 'good eating quality' for all samples irrespective of diet, a conclusion supported by the shear force, cooking loss, particle size, and intramuscular fat results. Drip loss was affected by a significant interaction between diet and muscle. The ultimate pH of meat from lambs fed annual wheat was highest. Comparable colour stability and purge results suggested that diet did not impact on lamb retail-potential. Sodium, sulphur and zinc concentrations were higher in the meat from lambs fed annual wheat, compared to perennial wheat. Overall, these outcomes support the use of perennial wheat as a forage for lamb production.

Influence of dietary inclusion of tannin extracts from mimosa, chestnut and tara on volatile compounds and flavour in lamb meat

Tannins are compounds able to form complexes with proteins limiting their ruminal degradation and thus the synthesis of some odour-active compounds may be inhibited. Tannins are broadly divided in condensed tannins (CT) and hydrolysable tannins (HT). The study aimed to assess the influence of dietary inclusion of three commercial tannin extracts, namely mimosa (Acacia mearnsii; CT), chestnut (Castanea sativa; HT) or tara (Caesalpinia spinosa; HT) on volatile profile and flavour of meat and kidney fat from lambs. Comisana male lambs were divided into four groups (n = 9 each) and fed for 75 days with a concentrate-based diet (CON) or CON supplemented with 4% of one of the tannin extracts. Tannins reduced "pastoral" odour in perirenal fat of lambs the meat of which was characterized by a very low perception of this attribute. It may be assumed that p-cresol and 8-methylnonanoic acid mostly contributed to "pastoral" odour expression in the diet without condensed or hydrolysable tannins.

Influence of dietary cardoon meal on volatile compounds and flavour in lamb meat

Cardoon meal is a by-product retained after oil extraction from the seeds of cultivated Cynara cardunculus var. altilis that has been proposed as a valuable resource for animal feeding. The study aimed to assess the influence of its dietary inclusion on volatile profile and flavour of meat and kidney fat from lambs. Fifteen Sarda × Comisana male lambs were randomly divided in two groups and fed for 75 days with a concentrate-based diet containing 15% cardoon meal (CMD, n = 7) or dehydrated alfalfa (CON, n = 8). Cardoon meal inclusion reduced the "barnyard/animal" odour perceived by a trained panel in kidney fat, which could be associated with the aromatic compound p-cresol (4-methylphenol), detected only in CON diet. Considering the other aroma volatiles regarded as the main contributors for the characteristic lamb flavour, both diets were characterized by moderate to low levels of 4-methyloctanoic acid, skatole and indole while 4-methylnonanoic acid and 4-ethyloctanoic acid were not detected.