Selection for intramuscular fat and lean meat yield will improve the bloomed colour of Australian lamb loin meat

Discrimination among Fresh, Frozen-Stored and Frozen-Thawed Beef Cuts by Hyperspectral Imaging

The detection of the storage state of frozen meat, especially meat frozen-thawed several times, has always been important for food safety inspections. Hyperspectral imaging (HSI) is widely applied to detect the freshness and quality of meat or meat products. This study investigated the feasibility of the low-cost HSI system, combined with the chemometrics method, to classify beef cuts among fresh (F), frozen-stored (F-S), frozen-thawed three times (F-T-3) and frozen-thawed five times (F-T-5). A compact, low-cost HSI system was designed and calibrated for beef sample measurement. The classification model was developed for meat analysis with a method to distinguish fat and muscle, a CARS algorithm to extract the optimal wavelength subset and three classifiers to identify each beef cut among different freezing processes. The results demonstrated that classification models based on feature variables extracted from differentiated tissue spectra achieved better performances, with ACCs of 92.75% for PLS-DA, 97.83% for SVM and 95.03% for BP-ANN. A visualization map was proposed to provide detailed information about the changes in freshness of beef cuts after freeze-thawing. Furthermore, this study demonstrated the potential of implementing a reasonably priced HSI system in the food industry.

Comprehensive Analysis of Transcriptome and Metabolome Reveals Regulatory Mechanism of Intramuscular Fat Content in Beef Cattle

The intramuscular fat (IMF) content of beef determined the meat quality, and the market value of beef varies with different breeds. To provide some new approaches for improving meat quality and cattle breed improvement, 24-month-old Qinchuan cattle (Q, n = 6), Nanyang cattle (N, n = 6), and Japanese black cattle (J, n = 6) were selected. IMF content of the J group (16.92 ± 1.08%) is remarkably higher than that of indigenous Chinese cattle (Q, 13.38 ± 1.08%, and N, 12.35 ± 1.22%). Monounsaturated fatty acids and polyunsaturated fatty acids in the J group are higher than the Q and creatine, lysine, and glutamine are the three most abundant amino acids in beef, which contribute to the flavor formation. Similarly, IMF content-related genes were enriched in four vital KEGG pathways, including fatty acid metabolism, biosynthesis of unsaturated fatty acids, fatty acid elongation, and insulin resistance. Moreover, weighted genes coexpression network analysis (WGCNA) revealed that ITGB1 is the critical gene associated with the IMF content. This study compares transcriptome and metabolome of local and high-IMF cattle breeds, providing data for native cattle breeding and improvement of beef quality.

Lambs supplemented with Amazonian oilseed co-products: Meat quality and fatty acid profile

The Amazon has a wide variety of oilseeds that generate a huge amount of co-products with potential for use in animal nutrition. The objective was to use alternative resources (oilseed cakes) in the feeding of lambs to assign a sustainable destination to this biomass, and evaluate its influence on the quality and fatty acid (FA) profile of the meat. Twenty-four lambs, male, castrated, crossbred Dorper × Santa Inês, weighing 30 ± 1.3 kg of initial body weight, were distributed in a completely randomized design in 4 treatments (diets) with six replications (animals). The control diet (Control) contained corn and soybean meal as main ingredients, which were partially replaced in the other diets by cupuassu cake diet (Cup), palm kernel cake diet (Palm) and tucuma cake diet (Tuc). The inclusion of Amazon cakes influences the lipid (P = 0.02) and protein (P < 0.01) composition of meat (longissimus lumborum); reduces cooking losses (P < 0.01); influences the colors (L, a, b), chroma, and Hue Angle (P < 0.01); promotes changes in total FA composition and FA profile (P < 0.05); reduces hypocholesterolemic FA (h) (P = 0.01), but does not influence hypercholesterolemic (H) and indices h:H, AI and TI (P > 0.05). The inclusion of oilseed cakes influences the chemical composition, physical parameters, composition and fatty acid profile of the meat, but does not influence the indicators of atherogenicity, thrombogenicity and cholesterolemia.

A Role of Multi-Omics Technologies in Sheep and Goat Meats: Progress and Way Ahead

Sheep and goat meats are increasingly popular worldwide due to their superior nutritional properties and distinctive flavor profiles. In recent decades, substantial progress in meat science has facilitated in-depth examinations of ovine and caprine muscle development during the antemortem phase, as well as post-mortem changes influencing meat attributes. To elucidate the intrinsic molecular mechanisms and identify potential biomarkers associated with meat quality, the methodologies employed have evolved from traditional physicochemical parameters (such as color, tenderness, water holding capacity, flavor, and pH) to some cutting-edge omics technologies, including transcriptomics, proteomics, and metabolomics approaches. This review provides a comprehensive analysis of multi-omics techniques and their applications in unraveling sheep and goat meat quality attributes. In addition, the challenges and future perspectives associated with implementing multi-omics technologies in this area of study are discussed. Multi-omics tools can contribute to deciphering the molecular mechanism responsible for the altered the meat quality of sheep and goats across transcriptomic, proteomic, and metabolomic dimensions. The application of multi-omics technologies holds great potential in exploring and identifying biomarkers for meat quality and quality control, thereby promoting the optimization of production processes in the sheep and goat meat industry.

Effect of age and diet on carcass and meat quality in ewes

This study elucidated the effect of age and diet on carcass characteristics and meat quality parameters of Rambouillet ewes. Forty ewes (n = 20 yearling ewes and n = 20 cull ewes) were fed with alfalfa hay (AH) or a 100 % concentrate diet (CD). Treatments were: a) 10 cull ewes were fed only with AH, b) 10 yearling ewes were fed only with AH, c) 10 cull ewes were fed with CD, d) 10 yearling ewes were fed with CD. Productive performance, carcass and meat quality were analyzed. Animals had ten days for adaptation and 35 days were used to collect data. Dry matter intake was greater (P < 0.05) for CD. Feed conversion rates were not affected by treatments. The pH at 45 min and 24 h, carcass length, leg length, leg width, thorax width, and thorax perimeter were not affected by treatments. Hot carcass weight was heavier (P < 0.05) in cull ewes, cold carcass weight was increased (P < 0.05) with CD. Carcass yield (CY) was heavier in CD (P < 0.05). Cull ewes had greater (P < 0.05) lean CIELAB L*, a*, b*, c*, and h* values compared to yearling ewes. The color changes increased with age at five days (P < 0.05), but a decrease (P < 0.05) with diet was observed at ten days. Cathepsins B, B + L, and Lowry protein content were not affected by treatments. In conclusion, feeding cull ewes with concentrate diets may enhance body weight gain and carcass yield compared to a diet based on 100 % alfalfa hay.

Potential of in-plant intramuscular fat predictions to enable sheep breeders to incorporate consumer preferences in breeding programmes

The inclusion of eating quality traits in sheep genetic improvement programmes is desirable. Intramuscular fat (IMF) plays a key role in ensuring consumer satisfaction when eating lamb, but genetic progress for IMF is constrained by a lack of routine data collection. This study investigated the potential for IMF predictor traits to substitute for measured IMF in genetic improvement programmes. Carcass and predicted IMF (near-infrared estimated IMF and marbling score) data were available on 10,113 New Zealand lambs, 1678 of which also had measured chemical IMF on a slice of M. longissimus lumborum on which the predictions of IMF had been made. Genetic antagonisms were observed between carcass lean traits and IMF. The genetic correlation between the predictors and measured IMF approached one, indicating that predictors of IMF can be used in genetic improvement programmes. Through using selection indexes, simultaneous increases in IMF and the existing terminal selection index are possible, provided all traits are measured. This study highlights the importance and potential of predicted IMF to achieve genetic improvement in traits of importance to consumers.

Dietary administration of l-carnitine during the fattening period of early feed restricted lambs modifies lipid metabolism and meat quality

Early feed restriction of lambs promotes a permanent mitochondrial dysfunction that impairs β-oxidation of fatty acids along the whole life. Therefore, dietary l-carnitine might help to improve the mitochondrial function of these lambs, thus modifying lipid metabolism and meat quality traits. In order to test this hypothesis an experiment was carried out with 22 Merino lambs that were subjected to an early feed restriction during the suckling period. Once weaned, the lambs were allocated to a control group (CTRL, n = 11) being fed ad libitum a complete pelleted diet during the fattening phase, whereas the second group (CARN, n = 11) received the same diet formulated with 3 g/kg of l-carnitine. Carcass characteristics were not affected (P > 0.05) by treatment. However, lambs fed l-carnitine showed higher amounts of intramuscular fat (26.5 vs. 33.6 g/kg fresh matter; P = 0.047) with a lower ratio between polyunsaturated and saturated fatty acids (0.425 vs 0.333; P = 0.023) and a higher atherogenic (0.507 vs 0.597; P < 0.001) and thrombogenic index (1.23 vs 1.42; P < 0.001). An increase in lightness (P < 0.05) and a tendency to improved oxidative stability in cooked meat (P = 0.066) were also observed in the CARN group. Consequently, dietary l-carnitine supplied during the fattening period of early feed restricted lambs modifies meat quality traits thus increasing lightness, oxidative stability and intramuscular fat content, but worsening the fatty acid profile.

The evaluation of the genotype and slaughter weight effect on meat quality and fatty acid profile from two native sheep

The purpose of this study is to investigate the quality characteristics and fatty acid composition of meat from male Akkaraman (AKK) and Bafra × Akkaraman B₁ (BA B₁) lambs slaughtered at different live weights. Thirty-six male lambs (18 AKK and 18 BA B₁) were slaughtered at three different slaughter weights (35, 40, and 45 kg) after being fattened intensively. Meat physical quality characteristics and fatty acid profiles were used as response variables. Color parameters (L*, a*, and b*) and pH were not significantly influenced by genotype and slaughter weight (SW). Water-holding capacity (WHC) was significantly affected by SW (P < 0.05), cooking loss (CL) by genotype (P < 0.001). Increasing SW, intramuscular fat of the Longissimus thoracis muscle showed increased total unsaturated fatty acids (TUFA) (P < 0.01) and ratios of TUFA/saturated fatty acids (SFA) (P < 0.01), and decreased thrombogenic and atherogenic indices (P < 0.01). Monounsaturated fatty acids (MUFA) (P < 0.05) and polyunsaturated fatty acids (PUFA) (P < 0.01) varied on with the genotypes. In conclusion, genotype and SW did not greatly affect meat quality; however, MUFA and PUFA mutually changed according to the genotype, and fatty acid percentages improved according to the SW.

Epigenome-wide association studies of meat traits in Chinese Yorkshire pigs highlights several DNA methylation loci and genes

In this study, we aimed to identified CpG sites at which DNA methylation levels are associated with meat quality traits in 140 Yorkshire pigs, including pH at 45 min (pH_45min), pH at 24 h (pH_24h), drip loss (DL), meat redness value (a*), yellowness (b*) and lightness (L*). Genome-wide methylation levels were measured in muscular tissue using reduced representation bisulfite sequencing (RRBS). Associations between DNA methylation levels and meat quality traits were examined using linear mixed-effect models that were adjusted for gender, year, month and body weight. A Bonferroni-corrected p-value lower than 7.79 × 10 - 8 was considered statistically significant threshold. Eight CpG sites were associated with DL, including CpG sites annotated to RBM4 gene (cpg301054, cpg301055, cpg301058, cpg301059, cpg301066, cpg301072 and cpg301073) and NCAM1 gene (cpg1802985). Two CpG sites were associated with b*, including RNFT1 and MED13 (cpg2272837) and TRIM37 gene (cpg2270611). Five CpG sites were associated with L*, including GSDMA and LRRC3C gene (cpg2252750) and ENSSSCG00000043539 and IRX1 gene (cpg2820178, cpg2820179, cpg2820181 and cpg2820182). No significant associations were observed with pH_45min, pH_24h or a*. We reported associations of meat quality traits with DNA methylation and identified some candidate genes associated with these traits, such as NCAM1, MED13 and TRIM37 gene. These results provide new insight into the epigenetic molecular mechanisms of meat quality traits in pigs.

Effect of Lentinan on Lipid Oxidation and Quality Change in Goose Meatballs during Cold Storage

The effects of different concentrations of lentinan (LNT) (0, 0.5, 1, 2 and 4%) on the oxidation characteristics and physicochemical properties of goose meatballs were investigated during different cold storage (4 °C) stages (3, 7 and 12 days). After adding LNT, the thiobarbituric acid reactive substances (TBARS) and total volatile base nitrogen (TVB-N) of goose meatballs significantly decreased compared to the LNT-free sample during cold storage, which indicated that LNT can inhibit the fat oxidation and the release of nitrogenous substances. Meanwhile, the presence of LNT makes microstructure of the goose meatball samples become denser during the whole storage time. The headspace solid phase microextraction gas chromatography-mass spectrometry (SPME-GC-MC) results showed that the proportion of aldehydes in the 4% LNT group reached 0 during storage, suggesting that high LNT concentration inhibits the formation of oxidized products in meat products. The sensory evaluation showed that the addition of LNT improved the color, appearance, flavor, and overall acceptance of goose meatballs, and the 2% LNT group had the highest score in overall acceptance. In summary, the addition of LNT could delay lipid oxidation and improve the quality of goose meatballs during cold storage.

miR-24-3p Dominates the Proliferation and Differentiation of Chicken Intramuscular Preadipocytes by Blocking ANXA6 Expression

Intramuscular fat (IMF) is one of the crucial factors determining meat quality. IMF deposition depends on the hyperplasia and hypertrophy of intramuscular preadipocytes, in which genes and noncoding RNAs play an important regulatory role. According to previous transcriptome analysis, ANXA6 and miR-24-3p were identified as involved in lipid metabolism in breast muscle. In this study, we further investigated their function in the proliferation and differentiation of chicken intramuscular preadipocytes. The results indicated that overexpression of ANXA6 inhibited proliferation and promoted differentiation of intramuscular preadipocytes, while knockdown of ANXA6 promoted cell proliferation and inhibited adipogenic differentiation. miR-24-3p was proved to directly bind to the 3′ untranslated region (3′UTR) of ANXA6 by dual-luciferase reporter assay. The regulatory effect of miR-24-3p on the proliferation and differentiation of intramuscular preadipocytes was opposite to that of ANXA6. Besides, the overexpression vector of ANXA6 eliminated the impact of miR-24-3p mimics on intramuscular preadipocytes. In brief, we revealed that miR-24-3p promoted proliferation but inhibited differentiation of intramuscular preadipocytes by blocking ANXA6 expression, thus dominating IMF deposition in broilers. These findings may provide a novel target for improving chicken meat quality.

Carcass and Meat Quality of Lambs from Thin-Tailed and Fat-Tailed Breeds at Five Different Slaughter Weights

In lamb production, deciding the optimal slaughter weight (SW) has great importance on product quality. The aim of the study was to determine the optimum SW for lambs from a thin-tailed breed (Kivircik) and a fat-tailed breed (Kangal Akkaraman) in order to get high-quality meat and carcass. Kivircik (n=60) and Kangal Akkaraman (n=59) lambs were allotted to five SW groups (20, 28, 36, 44 and 52 kg). In Kivircik lambs, backfat thickness and fatness score gradually increased in parallel with the increase in SW, while the increase in the tail fat and kidney knob and channel fat (KKCF) proportions were observed by up to 36 kg. In Kangal Akkaraman lambs, evident increases in fatness parameters, except tail fat proportion, were observed when the SW increased from 44 kg to 52 kg. Meat pH, Warner Bratzler shear force (WBSF) and cooking loss values were not influenced by SW in lambs of both breeds. As SW increased in Kivircik lambs, there was a significant decrease in meat lightness and an increase in yellowness. In Kangal Akkaraman breed, lambs slaughtered at 20 kg and 28 kg had higher L* values, and lower a* and C* values than those of other SW groups. In Kivircik lambs, the total PUFA proportion and the ΣPUFA/ ΣSFA ratio were lower in SW-44 and SW-52 groups than those of SW-20 and SW-28 groups. Decreases of these parameters were in SW-52 group in Kangal Akkaraman lambs. In meat samples of both breeds, SW-52 groups had a lower Σn-3 proportion and a higher Σn-6 / Σn-3 ratio than other SW groups. In Kivircik lambs, the panellists evaluated the meat of SW-20 and SW-28 groups as tender compared to those in SW-44 and SW-52 groups. In Kangal Akkaraman breed, flavour intensity in the meat of SW-52 lambs was higher than those of SW-20 and SW-28 groups. Results of the study indicate that slaughtering of lambs at 20 kg and 28 kg in both breeds provided better meat quality but caused lower carcass weight. Therefore, slaughtering Kivircik and Kangal Akkaraman lambs at 20 kg and 28 kg live weight might be recommended especially to farmers, who aim to obtain high-quality lamb meat. In this case, it should not be ignored that the amount of meat produced will be less. On the other hand, slaughtering lambs at about 44 kg weight could be recommended to farmers, who aimed to obtain as much quality lamb carcasses as possible without any negative influence on meat quality.

Consumers' Attitudes toward the Use of an Edible Coating for Lamb Meat According to Label Information

The use of edible coatings in meat is currently being investigated in several studies. However, consumers’ attitudes toward this technology are not clear. This study evaluated consumers’ intention to purchase vacuum-packaged meat with a chitosan coating based on the label information. Three factors combined with different levels were considered: type of cut (“loin”, “French rack”, or “leg steak”), coating/information (no information, chitosan without information explained, and chitosan with information explained), and price (low or high). Consumers’ purchase intentions were evaluated using a 7-point structured scale (1 = certainly would not buy; 7 = certainly would buy). The data were analyzed by conjoint analysis and cluster analysis. The average purchase intention value was 4.3 ± 0.5. The “French rack” cut showed the highest value for purchase intention and a high price was also a relevant factor. The packaging with the label stating the presence of a “chitosan” coating without giving any further information obtained higher purchase intentions than the one with the more detailed information label. In the cluster analysis, the factor “type of cut” showed the highest relative importance in two groups, while “price” had a higher impact in another. The type of cut was the main factor affecting consumers’ purchase intentions. However, different attitudes were observed depending on the group.

Consumer Perceptions of Meat Redness Were Strongly Influenced by Storage and Display Times

Lamb (n = 79) meat colour was scored by 879 untrained consumers using a scale of 0 (brown) to 100 (red). This consumer colour score (CCS) was obtained on m. longissimus lumborum (loin) and m. semimembranosus (topside), stored for short (5–7 days), medium (33–35 days), and long periods (110–112 days) and a retail display time of up to 4 days. Consumers perceived topside to be less red initially and changed from red to brown more rapidly when stored for the long-storage period (p < 0.01). Whereas, the initial CCS of loin samples were similar across the storage periods (p > 0.05). CCS and the instrument measure oxy/met (reflectance of light at wavelengths 630 nm and 580 nm) had a low correlation coefficient of 0.33 (p < 0.01). The propensity for lamb growth and leanness indicated by sire breeding values for lamb weight, eye muscle depth, eye muscle fat depth, and loin intramuscular fat had varied and inconsistent effects on CCS. Therefore, even the selection on CCS.

Different expression of lipid metabolism-related genes in Shandong black cattle and Luxi cattle based on transcriptome analysis

To provide new ideas for improving meat quality and generating new breeds of cattle, the important candidate genes affecting fat deposition in two kinds of cattle were identified. Eighteen months Shandong black cattle (n = 3) and Luxi cattle (n = 3) were randomly assigned into two environmental. The longissimus dorsi muscles of Shandong Black Cattle and Luxi Cattle were collected and analyzed by fatty acid determination, high-throughput sequencing transcriptomics, qRT-PCR expression profile and western blot. The ratio of unsaturated fatty acids to saturated fatty acids was 1.37:1 and 1.24:1 in the muscle tissues of Shandong black cattle and Luxi cattle, respectively. The results of RNA-Seq analysis revealed 1320 DEGs between the longissimus dorsi of Shandong black cattle and Luxi cattle. A total of 867 genes were upregulated, and the other 453 genes were downregulated. With GO enrichment analysis, it was found that the identified DEGs were significantly enriched in regulation of the Wnt signaling pathway, negative regulation of the Wnt signaling pathway, cAMP metabolic process, fat cell differentiation and among other functions. We found that regulation of lipolysis in adipocytes was the significant enrichment pathway of upregulated genes and downregulated genes, PPAR signaling pathway and AMPK signaling pathway are highly representative pathways of lipid metabolism in Shandong black cattle. Network analysis showed that PPARGC1A, ADCY4, ANKRD6, COL1A1, FABP4, ADIPOQ, PLIN1, PLIN2, and LIPE genes were correlated with key loci genes in multiple metabolic pathways. Meanwhile we found that FABP4 and ADIPOQ had 7 common regulatory factors in different genes, which were PLIN1, PLIN2, PPARGC1A, RXRA, PCK1, LEPR, LEP. These genes were involved in regulation of lipolysis in adipocytes, adipocytokine signaling pathway, PPAR signaling pathway. FABP4 and ADIPOQ were selected as important candidate marker genes for fat deposition based on the results.

Feeding unsaleable carrots to lambs increased performance and carcass characteristics while maintaining meat quality

This study investigated the effect of feeding unsaleable carrots to lambs within a total-mixed ration (TMR) on performance, carcass characteristics, meat quality and sensory parameters. Thirty-six Australian Merino wether lambs were fed a control (barley-based) or carrot-based TMR for 11-weeks. Carrot-fed lambs had 2.7% higher cold dressing percentage (P = 0.03) while consuming less than control lambs. Subcutaneous fat of carrot-fed lambs contained less branch-chained, and more cis- and trans-monounsaturated fatty acids (FA; P ≤ 0.01) compared to control-fed lambs, which tended (P = 0.08) to have higher concentrations of polyunsaturated FA, despite the Longissimus lumborum (LL) muscle being unchanged by diet. Under retail display conditions, L* and hue values were lower (P ≤ 0.04) for 5 d aged LL samples from carrot-fed lambs. No differences were observed in other meat quality and sensory parameters between diets. Therefore, feeding unsaleable carrots at 45% DM in a TMR can improve lamb performance and carcass characteristics, while maintaining meat quality and FA composition.

Genetics of Omega-3 Long-Chain Polyunsaturated Fatty Acid Metabolism and Meat Eating Quality in Tattykeel Australian White Lambs

Meat eating quality with a healthy composition hinges on intramuscular fat (IMF), fat melting point (FMP), tenderness, juiciness, flavour and omega-3 long-chain polyunsaturated fatty acids (n-3 LC-PUFA) content. These health-beneficial n-3 LC-PUFA play significant roles in optimal cardiovascular, retinal, maternal and childhood brain functions, and include alpha linolenic (ALA), eicosapentaenoic (EPA), docosahexaenoic (DHA) and docosapentaenoic (DPA) acids. The primary objective of this review was to access, retrieve, synthesise and critically appraise the published literature on the synthesis, metabolism and genetics of n-3 LC-PUFA and meat eating quality. Studies on IMF content, FMP and fatty acid composition were reviewed to identify knowledge gaps that can inform future research with Tattykeel Australian White (TAW) lambs. The TAW is a new sheep breed exclusive to MARGRA brand of lamb with an outstanding low fat melting point (28-39°C), high n-3 LC-PUFA EPA+DHA content (33-69mg/100g), marbling (3.4-8.2%), tenderness (20.0-38.5N) and overall consumer liking (7.9-8.5). However, correlations between n-3 LC-PUFA profile, stearoyl-CoA desaturase (SCD), fatty acid binding protein 4 (FABP4), fatty acid synthase (FASN), other lipogenic genes and meat quality traits present major knowledge gaps. The review also identified research opportunities in nutrition-genetics interactions aimed at a greater understanding of the genetics of n-3 LC-PUFA, feedlot finishing performance, carcass traits and eating quality in the TAW sheep. It was concluded that studies on IMF, FMP and n-3 LC-PUFA profiles in parental and progeny generations of TAW sheep will be foundational for the genetic selection of healthy lamb eating qualities and provide useful insights into their correlations with SCD, FASN and FABP4 genes.

Genetic correlations between meat quality traits and growth and carcass traits in Merino sheep1

Genetic correlations between 16 meat quality and nutritional value traits and live weight at various ages, live ultrasound fat and muscle depth, carcass measures, and carcass dissection traits were estimated for Merino sheep in the Information Nucleus (IN). Genetic correlations between live weight at various ages and the carcass traits are also reported. The IN comprised 8 genetically linked flocks managed across a range of Australian sheep environments. Meat quality traits included between 1,200 and 1,300 records for progeny from over 170 sires for intramuscular fat (IMF), lean meat yield (LMY), shear force (SF5), pH, meat color, and meat nutritional value traits including iron and zinc levels and long-chain omega-3 and omega-6 polyunsaturated fatty acid levels. The genetic correlations indicated that selection of Merino sheep to either reduce fat or increase muscle using ultrasound assessments will result in little change in IMF and SF5. Myoglobin levels would tend to be reduced following selection for reduced ultrasound fat depth (0.35 ± 0.21, 0.43 ± 0.14), whereas increases in myoglobin levels would occur due to selection for increased ultrasound muscle depth (0.25 ± 0.24, 0.38 ± 0.15). Selection for increased live weight will result in favorable correlated responses in hot carcass weight (0.76 to 0.97), dressing percentage (0.13 to 0.47), and carcass muscle (0.37 to 0.95), but unfavorable responses of increases in carcass fatness (0.13 to 0.65) and possible small reductions in muscle oxidative activity (-0.13 ± 0.14 to -0.73 ± 0.33) and iron content (-0.14 ± 0.15 to -0.38 ± 0.16), and a possible deterioration of shear force from selection at later ages (0.15 ± 0.26, 0.27 ± 0.24). Negligible changes are generally expected for LMY and meat color traits following selection for increased live weight (most genetic correlations less than 0.20 in size). Selection for increased LMY would tend to result in unfavorable changes in several aspects of meat quality, including reduced IMF (-0.27 ± 0.18), meat tenderness (0.53 ± 0.26), and meat redness (-0.69 ± 0.40), as well as reduced iron levels (-0.25 ± 0.22). These genetic correlations are a first step in assisting the development of breeding values for new traits to be incorporated into genetic evaluation programs to improve meat production from Merino sheep and other dual-purpose sheep breeds.