Intramuscular Fat Percentage Research Articles

Changes in physicochemical properties and fatty acid composition of pork following long-term frozen storage

The objective of this study was to investigate the effect of long-term frozen storage (2 years) of pork on colour stability, lipid and protein oxidation, drip/thawing losses and intramuscular fatty acid composition, as well as to examine the relationships among them. Pork quality parameters were significantly altered by frozen storage during 2 years, causing an increase in pH values, drip and thawing losses and metmyoglobin percentage, and a decrease in colour indices (a* and b* values) and oxymyoglobin percentage. The percentage of intramuscular fat and total saturated and monounsaturated fatty acids were significantly higher in pork after 2 years of storage at −20 °C, whereas it had the lowest values of polyunsaturated fatty acids, especially n-3 long chain fatty acids. Furthermore, the relationships among colour stability, lipid and protein oxidation, thawing losses and fatty acid profile revealed the complex interrelations generated during frozen storage.

Legume finishing provides beef with positive human dietary fatty acid ratios and consumer preference comparable with grain-finished beef.

Consumer liking, proximate composition, pH, Warner-Bratzler shear force, fatty acid composition, and volatile compounds were determined from the LM (longissimus thoracis) of cattle ( = 6 per diet) finished on conventional feedlot (USUGrain), legume, and grass forage diets. Forage diets included a condensed tannin-containing perennial legume, birdsfoot trefoil (; USUBFT), and a grass, meadow brome ( Rehmann; USUGrass). Moreover, representative retail forage (USDA Certified Organic Grass-fed [OrgGrass]) and conventional beef (USDA Choice, Grain-fed; ChGrain) were investigated ( = 6 per retail type). The ChGrain had the greatest ( < 0.05) intramuscular fat (IMF) percentage followed by USUGrain, the IMF percentage of which was greater ( < 0.05) than that of USUGrass and OrgGrass. The IMF content of USUBFT was similar ( > 0.05) to that of both USUGrain and USUGrass. Both grain-finished beef treatments were rated greater ( < 0.05) for flavor, tenderness, fattiness, juiciness, and overall liking compared with USUGrass and OrgGrass. Consumer liking of USUBFT beef tenderness, fattiness, and overall liking were comparable ( > 0.05) with that of USUGrain and ChGrain. Flavor liking was rated greatest ( < 0.05) for USUGrain and ChGrain, and that of USUBFT was intermediate ( > 0.05) to those of ChGrain, USUGrass, and OrgGrass. Cumulative SFA and MUFA concentrations were greatest ( < 0.05) in ChGrain and USUGrain, whereas USUGrass and OrgGrass had lower ( < 0.05) concentrations. Concentrations of cumulative SFA and MUFA in USUBFT were intermediate and similar ( > 0.05) to those of USUGrain and USUGrass. Each forage-finished beef treatment, USUGrass, OrgGrass, and USUBFT, had lower ( < 0.001) ratios of -6:-3 fatty acids. Hexanal was the most numerically abundant volatile compound. The concentration of hexanal increased with increasing concentrations of total PUFA. Among all the lipid degradation products (aldehydes, alcohols, furans, carboxylic acids, and ketones) measured in this study, there was an overall trend toward greater quantities in grain-finished products, lower quantities in USUGrass and OrgGrass, and intermediate quantities in USUBFT. This trend was in agreement with IMF content, fatty acid concentrations, and sensory attributes. These results suggest an opportunity for a birdsfoot trefoil finishing program, which results in beef comparable in sensory quality with grain-finished beef but with reduced -6 and SFA, similar to grass-finished beef.

Skeletal Muscle Quantitative Nuclear Magnetic Resonance Imaging and Spectroscopy as an Outcome Measure for Clinical Trials.

Recent years have seen tremendous progress towards therapy of many previously incurable neuromuscular diseases. This new context has acted as a driving force for the development of novel non-invasive outcome measures. These can be organized in three main categories: functional tools, fluid biomarkers and imagery. In the latest category, nuclear magnetic resonance imaging (NMRI) offers a considerable range of possibilities for the characterization of skeletal muscle composition, function and metabolism. Nowadays, three NMR outcome measures are frequently integrated in clinical research protocols. They are: 1/ the muscle cross sectional area or volume, 2/ the percentage of intramuscular fat and 3/ the muscle water T2, which quantity muscle trophicity, chronic fatty degenerative changes and oedema (or more broadly, “disease activity”), respectively. A fourth biomarker, the contractile tissue volume is easily derived from the first two ones. The fat fraction maps most often acquired with Dixon sequences have proven their capability to detect small changes in muscle composition and have repeatedly shown superior sensitivity over standard functional evaluation. This outcome measure will more than likely be the first of the series to be validated as an endpoint by regulatory agencies. The versatility of contrast generated by NMR has opened many additional possibilities for characterization of the skeletal muscle and will result in the proposal of more NMR biomarkers. Ultra-short TE (UTE) sequences, late gadolinium enhancement and NMR elastography are being investigated as candidates to evaluate skeletal muscle interstitial fibrosis. Many options exist to measure muscle perfusion and oxygenation by NMR. Diffusion NMR as well as texture analysis algorithms could generate complementary information on muscle organization at microscopic and mesoscopic scales, respectively. 31P NMR spectroscopy is the reference technique to assess muscle energetics non-invasively during and after exercise. In dystrophic muscle, 31P NMR spectrum at rest is profoundly perturbed, and several resonances inform on cell membrane integrity. Considerable efforts are being directed towards acceleration of image acquisitions using a variety of approaches, from the extraction of fat content and water T2 maps from one single acquisition to partial matrices acquisition schemes. Spectacular decreases in examination time are expected in the near future. They will reinforce the attractiveness of NMR outcome measures and will further facilitate their integration in clinical research trials.

Genetic parameters for docility, weaning weight, yearling weight, and intramuscular fat percentage in Hereford cattle.

Cattle behavior, including measures of docility, is important to beef cattle producers not only from a human safety perspective but also due to potential correlations to economically relevant traits. Field data from the American Hereford Association was used to estimate genetic parameters for chute score (CS; = 25,037), weaning weight (WW; = 24,908), yearling weight (YW; = 23,978), and intramuscular fat percentage (IMF; = 12,566). Single-trait and bivariate animal models were used to estimate heritabilities and genetic correlations. All models included fixed effects of sex and contemporary group, defined as herd-year-season, and direct genetic and residual components were included as random effects. For CS and WW, additional random effects of maternal genetic and maternal permanent environment were also fitted. For CS, WW, YW, and IMF, heritability estimates were 0.27 ± 0.02, 0.35 ± 0.03, 0.36 ± 0.02, and 0.27 ± 0.02, respectively. Genetic correlations between CS and WW, CS and YW, CS and IMF, WW and YW, WW and IMF, and YW and IMF were -0.12 ± 0.06, -0.10 ± 0.05, -0.08 ± 0.06, 0.47 ± 0.05, -0.19 ± 0.09, and -0.41 ± 0.05, respectively. Heritability estimates for all traits suggest that they would respond favorably to selection and that selection for increased WW or YW could decrease marbling. Genetic correlations between CS and WW, YW, and IMF were all favorable but weak, suggesting that selection for improved docility will not have negative consequences on growth or carcass quality. Furthermore, maternal additive and maternal permanent environmental variances for CS were near 0, suggesting that their inclusion in National Cattle Evaluations is not warranted.

Evaluation of implant strategies in Angus-sired steers with high or low genetic potential for marbling and gain1

Sixty-nine Angus-sired steer calves (332.3 kg initial BW) were used to determine the effects of single or double implant strategies on steers of high or low genetic potential (GP) determined by the GeneMax (Zoetis, Florham Park, NJ) genetic profiling test. Steers were assigned to treatments in a 2 × 2 factorial design with factors of 1) composite GP score (high, mean GP score of 86.5 [HI]; low, mean GP score of 25.3[LO]) and 2) implant strategy (single, steers implanted on d 70 [1X], or double, steers implanted d 0 and 70 [2X]). All steers were given the same implant (Revalor-S; Merck Animal Health, Summit, NJ), with the 2X group implanted on d 0 and 70 and the 1X group implanted only on d 70. A diet containing 1.38 Mcal NEg/kg DM was fed ad libitum, once daily. Ultrasound was used to measure body composition characteristics on d 0 and 70. Steers were harvested after 140 d on feed. At both the d-0 and d-70 ultrasound, HI steers had greater ( < 0.001) percent intramuscular fat (IMF) than LO steers, but no differences ( ≥ 0.24) were observed in LM area (LMA), rib fat thickness (RF), or rump fat thickness (RMFT). Steers in the 2X group had larger ( = 0.02) LMA and less ( = 0.03) IMF on d 70 than 1X steers and no differences ( ≥ 0.50) in RF or RMFT were observed. From d 0 to 70, HI steers had ADG, DMI, and G:F ( ≥ 0.60) similar to LO steers; however, 2X steers had greater ( < 0.001) ADG and were more ( < 0.001) feed efficient compared with 1X steers during the same interval. Over the entire 140-d feeding period, there were no differences ( ≥ 0.6) in BW, ADG, DMI, or G:F between GP groups; however, 2X steers had greater ( = 0.03) ADG compared with 1X steers and still had similar ( ≥ 0.12) DMI and G:F. Upon slaughter, marbling score tended to be impacted by a GP × implant interaction (499.9 ± 18.5, 545.6 ± 18.5, 487.1 ± 18.5, and 469.8 ± 18.5 for HI and 2X, HI and 1X, LO and 2X, and LO and 1X, respectively; = 0.06). No differences ( ≥ 0.7) were observed between GP groups for HCW, LMA, RF, KPH, or yield grade (YG). Steers in the 1X group had less ( = 0.003) RF than 2X steers but similar ( ≥ 0.14) HCW, marbling, LMA, KPH, and YG. A greater proportion ( = 0.03) of HI steers had choice carcasses (100 ± 0.0%) compared with LO steers (87.8 ± 3.9%). Results of this study indicate that the GP test used in the current study predicted differences in IMF, carcass marbling, and percent carcasses graded as choice.

The effect of protein restriction during the growing period on carcass, meat and fat quality of heavy barrows and gilts

Nutritional strategies are being researched in pigs to increase fatness and then to improve quality of dry-cured products. A total of 160 Duroc×(Landrace×Large White) pigs, 50% barrows and 50% gilts, were used in a trial. During the growing period (73–118d of age), four feeds were formulated with decreasing levels of crude protein (CP; 21.6, 17.7, 14.7 and 13.5%) to achieve 1.10, 0.91, 0.78 and 0.52% of total Lysine, respectively. From 118d until slaughter, at 123kg (183, 181, 178 or 192d of age, respectively), a common diet was provided (17.7% CP and 0.91% Lysine). Barrows had fatter carcasses than gilts but intramuscular fat (IMF) proportion was similar for both. Dietary CP restriction promoted wider backfat depth and pork with higher IMF percentage which was more monounsaturated and less polyunsaturated. We conclude that CP restriction during the grower period improves desirable carcass and meat traits in barrows and gilts intended for dry-cured products.

Exploring causal networks underlying fat deposition and muscularity in pigs through the integration of phenotypic, genotypic and transcriptomic data.

BackgroundJoint modeling and analysis of phenotypic, genotypic and transcriptomic data have the potential to uncover the genetic control of gene activity and phenotypic variation, as well as shed light on the manner and extent of connectedness among these variables. Current studies mainly report associations, i.e. undirected connections among variables without causal interpretation. Knowledge regarding causal relationships among genes and phenotypes can be used to predict the behavior of complex systems, as well as to optimize management practices and selection strategies. Here, we performed a multistep procedure for inferring causal networks underlying carcass fat deposition and muscularity in pigs using multi-omics data obtained from an F2 Duroc x Pietrain resource pig population.ResultsWe initially explored marginal associations between genotypes and phenotypic and expression traits through whole-genome scans, and then, in genomic regions with multiple significant hits, we assessed gene-phenotype network reconstruction using causal structural learning algorithms. One genomic region on SSC6 showed significant associations with three relevant phenotypes, off-midline10th-rib backfat thickness, loin muscle weight, and average intramuscular fat percentage, and also with the expression of seven genes, including ZNF24, SSX2IP, and AKR7A2. The inferred network indicated that the genotype affects the three phenotypes mainly through the expression of several genes. Among the phenotypes, fat deposition traits negatively affected loin muscle weight.ConclusionsOur findings shed light on the antagonist relationship between carcass fat deposition and lean meat content in pigs. In addition, the procedure described in this study has the potential to unravel gene-phenotype networks underlying complex phenotypes.

Use of the technique of ultrasonography in the evaluation of the housing of cattle live

The objective of this study was to review the use of the technique of ultrasonography (US) in breeding beef cattle. Discusses the importance of the characteristics measured by the US in the composition of edible quality and volume of the carcasses, characteristics measurements by US: ribeye area (AOL), fat rump and subcutaneous fat (EG), fat thickness at P8 also known as croup (EGP8) and occasionally is measured percent intramuscular fat (GIM) or marbling. We conducted a brief history of the art, including Brazil, highlighting its main advantages and disadvantages compared with other assessment techniques phenotype animal-specific carcass traits. The details of measurement, operation of equipment, investments for the producer and the technical as well as appropriate age to perform the measurements on animal and other information indispensable the field of information published about the subject.

Comparison of meat quality parameters in surgical castrated versus vaccinated against gonadotrophin-releasing factor male and female Iberian pigs reared in free-ranging conditions

This study compared carcass and meat quality traits between 16 vaccinated (VF), 19 castrated (CF) and 8 entire (EF) female Iberian pigs, and between 21 vaccinated (VM) and 19 castrated (CM) male Iberian pigs reared in free ranging conditions. Vaccination consisted in the application of Improvac® at the age of 11, 12 and 14months in VF and VM. Pigs were slaughtered at 16months. In females, carcass and meat quality were found to be very similar regardless of the treatment. In males, VM had a leaner carcass, lower (P<0.05) percentage of intramuscular fat, higher shear force and more rancidity than CM (P<0.05 in all cases). It could be concluded that vaccination or castration had no major effects on quality traits in females. It should be then stated that entire females are suitable for free-range conditions in terms of product qualities. Vaccination in females did not alter carcass and meat quality, and specific interests should consider reproductive behavior in free-range conditions.

Measurement of intramuscular fat by muscle echo intensity.

The aim of this study was to compare ultrasound echo intensity (EI) with high-resolution T1 -weighted MRI and to establish calibration equations to estimate percent intramuscular fat from EI. Thirty-one participants underwent both ultrasound and MRI testing of 4 muscles: rectus femoris (RF); biceps femoris (BF); tibialis anterior (TA); and medial gastrocnemius (MG). Strong correlations were found between MRI percent fat and muscle EI after correcting for subcutaneous fat thickness (r = 0.91 in RF, r = 0.80 in BF, r = 0.80 in TA, r = 0.76 in MG). Three types of calibration equations were established. Muscle ultrasound is a practical and reproducible method that can be used as an imaging technique for examination of percent intramuscular fat. Future ultrasound studies are needed to establish equations for other muscle groups to enhance its use in both research and clinical settings.

Fat Infiltration in the Leg is Associated with Bone Geometry and Physical Function in Healthy Older Women.

The objective of this study was to estimate the associations between muscular fat infiltration, tibia bone mineral quantity and distribution, and physical function in healthy older women. Thirty-five women (aged 60-75 years, mean 70 years) were recruited from the community. Percent intramuscular fat (%IntraMF) within the right leg tibialis anterior, soleus, and gastrocnemius muscles and total intermuscular fat (IMF) were segmented from magnetic resonance imaging scans at the mid-calf. Intramyocellular lipid (IMCL) content in the right tibialis anterior was measured with proton magnetic resonance spectroscopy. Right tibia bone content, area, and strength were measured at the 4, 14, and 66% sites using peripheral quantitative computed tomography. Physical function was assessed by gait speed on the 20 m walking test. After adjusting for age, body size, and activity level, %IntraMF had a negative association with bone content and area at all tibia sites (r = -0.31 to -0.03). Conversely, greater IMF was associated with increased bone content and area (r = 0.04-0.32). Correlation coefficients for the association between IMCL and bone were negative (r = -0.44 to -0.03). All measures of fat infiltration had a negative association with observed physical function (r = -0.42 to -0.04). Our findings suggest that muscular fat infiltration in the leg of healthy postmenopausal women has a compartment-specific relationship with bone status and physical function. Minimizing fat accumulation within and between muscle compartments may prevent bone fragility and functional decline in women.

Genomic–polygenic evaluation of multibreed Angus–Brahman cattle for postweaning ultrasound and weight traits with actual and imputed Illumina50k SNP genotypes

The objectives were to estimate additive genetic variance fractions for 4 postweaning ultrasound and weight traits explained by 46,839 actual and imputed SNP genotypes, to compare rankings of calf additive genetic predictions from genomic–polygenic (GP), genomic (G), and polygenic (P) models, and to assess trends for GP, G, and P predicted additive genetic values as functions of calf Brahman fractions in a multibreed Angus–Brahman population. Traits were postweaning ultrasound ribeye area (UREA), backfat thickness (UBF), and percent intramuscular fat (UPIMF), and weight (UW). Phenotypes and Illumina3k genotypes were from 812 bull, heifer, and steer calves housed at the Feed Efficiency Facility of the University of Florida from 2006 to 2010. Program Findhap2 was used to impute from 2899 Illumina3k SNP to 46,839 Illumina50k SNP using a reference population of 828 Brangus heifers. Fixed effects for all models were contemporary group (year-pen), age of dam, sex of calf, age of calf, Brahman fraction of calf, and heterozygosity of calf. Random effects were additive SNP (GP and G models), additive polygenic (GP and P models), and residual. Software GS3 was used to compute variance components and heritabilities, and additive genetic predictions. Additive genetic variance fractions explained by the 46,839 actual and imputed SNP were 0.17 for UREA, 0.32 for UBF, 0.25 for UPIMF, and 0.19 for UW. Heritabilities were 0.33 for UREA, 0.22 for UBF, 0.43 for UPIMF, and 0.54 for UW. These additive genetic variance fractions were 1.8, 1.0, 4.4, and 2.1 times greater and heritabilities were 1.0, 1.2, 1.0, and 1.2 times greater than those obtained for these 4 traits using only the 2899 Illumina3k SNP. Rank correlations between EBV from GP and P models were the highest (0.93 to 0.96), followed by those between EBV from GP and G models (0.81 to 0.94), and by those between EBV from G and P models (0.66 to 0.81). Regression coefficients of EVB on Brahman fraction were small for all traits and models indicating that animals of comparable EBV existed in all breed groups. Imputation from Illumina3k to 50k increased the explained fraction of additive SNP variance resulting in higher rank correlations between additive genetic predictions from G and GP, and from G and P models for all ultrasound traits in this Angus–Brahman multibreed population.

Studies on Intramuscular Fat Percentage in Live Swine Using Real-time Ultrasound to Determine Pork Quality.

In the modern pork industry, selection of high intramuscular fat (IMF) in pigs is necessary to improve pork quality. Ultrasound has been used previously to predict subcutaneous fat thickness and IMF in the longissimus muscles of line pigs and Real-time ultrasound has also been reported as a reliable method for estimating IMF in live pigs. So we estimate the correlation between meat quality traits and IMF percentage to investigate the possibility of utilizing real-time ultrasound technology for predicting IMF percentage in line pigs to improve pork quality. The genetic and phenotypic correlations for chemical intramuscular fat (CIMF) and ultrasound intramuscular fat (UIMF) were estimated to be 0.75 and 0.76, respectively. These results suggest that genetic factors strongly influence meat quality. The genetic and phenotypic correlation between UIMF and CIMF were 0.75, 0.76, respectively. The heritability of UIMF and CIMF were 0.48 and 0.50, respectively. So we concluded that CIMF can be replaced with UIMF and Ultrasound machines can be used to test IMF in live swine. In future, UIMF can be utilized to improve pork quality as an alternative to CIMF.

Effects of production system and slaughter weight endpoint on growth performance, carcass traits, and beef quality from conventionally and naturally produced beef cattle

Glanc, D. L., Campbell, C. P., Cranfield, J., Swanson, K. C. and Mandell, I. B. 2015. Effects of production system and slaughter weight endpoint on growth performance, carcass traits, and beef quality from conventionally and naturally produced beef cattle. Can. J. Anim. Sci. 95: 37–47. Effects of production system and slaughter endpoint on performance, carcass traits, and beef quality were investigated in 64 Simmental cross steers (minimum 75% Continental breeding). Cattle were allocated to: (1) conventional production system based on use of implants and dietary ionophores or (2) natural production system in which no implants or ionophores were used. Within each production system, cattle were allocated for slaughter at 545 or 636 kg liveweight. Steers were fed an 85.5% concentrate diet based on high-moisture corn, soybean meal, and alfalfa silage. Average daily gain tended to be greater (P&lt;0.06) in conventional production system cattle, while there was a trend (P&lt;0.08) for production system by endpoint interactions for dry matter intake and gain to feed. Natural production system cattle tended to have greater (P&lt;0.08) marbling and percent intramuscular fat (%IMF) with lower (P&lt;0.09) longissimus shear force, while production system by endpoint interactions were present (P ≤ 0.03) for%IMF and carcass lean composition via rib dissection. At-home consumer evaluation of longissimus muscle steaks found tenderness, juiciness, flavour, and overall acceptability rankings were greater (P&lt;0.01) for steaks slaughtered from heavier cattle (636 vs. 545 kg liveweight). Marketing cattle at lighter slaughter weights may have benefits for performance at the expense of eating quality.

Beef quality parameters estimation using ultrasound and color images.

BackgroundBeef quality measurement is a complex task with high economic impact. There is high interest in obtaining an automatic quality parameters estimation in live cattle or post mortem. In this paper we set out to obtain beef quality estimates from the analysis of ultrasound (in vivo) and color images (post mortem), with the measurement of various parameters related to tenderness and amount of meat: rib eye area, percentage of intramuscular fat and backfat thickness or subcutaneous fat.ProposalAn algorithm based on curve evolution is implemented to calculate the rib eye area. The backfat thickness is estimated from the profile of distances between two curves that limit the steak and the rib eye, previously detected. A model base in Support Vector Regression (SVR) is trained to estimate the intramuscular fat percentage. A series of features extracted on a region of interest, previously detected in both ultrasound and color images, were proposed. In all cases, a complete evaluation was performed with different databases including: color and ultrasound images acquired by a beef industry expert, intramuscular fat estimation obtained by an expert using a commercial software, and chemical analysis.ConclusionsThe proposed algorithms show good results to calculate the rib eye area and the backfat thickness measure and profile. They are also promising in predicting the percentage of intramuscular fat.

The influence of maternal energy status during midgestation on beef offspring carcass characteristics and meat quality.

Research has suggested that maternal undernutrition may cause the development of a thrifty phenotype in the offspring, potentially resulting in greater adiposity and reduced muscle mass. These alterations in adipose and muscle development could have lasting impacts on offspring growth, carcass characteristics, and meat quality. However, limited research exists evaluating the impact of maternal energy status on these economically important traits of the offspring. Therefore, the objective of this study was to determine the influence of maternal energy status during midgestation on offspring carcass characteristics and meat quality. To alter maternal energy status, cows either grazed dormant, winter range (positive energy status [PES]) or were fed in a drylot at 80% of the energy requirements for BW maintenance (negative energy status [NES]) during a mean period of 102 ± 10.9 to 193 ± 10.9 d of gestation. Changes in BCS, BW, LM area (LMA), and 12th rib backfat were measured throughout midgestation. At the end of midgestation, cows in the NES group had a reduction (P ≤ 0.05) in BCS, BW, LMA, and 12th rib backfat when compared with PES dams. Cows and calves were managed similarly after midgestation through weaning and calves were managed and fed a common diet through the receiving, backgrounding, and finishing phases in the feedlot. Calves were harvested after 208 d in the feedlot, carcass characteristics were recorded, and strip loins were recovered for analysis of objective color and Warner-Bratzler shear force (WBSF). Maternal energy status had no influence on offspring HCW, dressing percent, LMA, percent KPH, marbling score, percent intramuscular fat, objective color, or WBSF (P > 0.10). Progeny of NES cows tended to have improvements in 12th rib backfat and USDA yield grade (P < 0.10). Greater ratio of marbling score to 12th rib fat thickness and ratio of percent intramuscular fat to 12th rib fat thickness (P < 0.05) were discovered in progeny from cows experiencing a NES during midgestation. These results suggest that maternal energy status during midgestation may impact fat deposition in intramuscular and subcutaneous fat depots without impacting muscle mass.

Intramuscular fat in lamb muscle and the impact of selection for improved carcass lean meat yield

Intramuscular fat percentage (IMF%) has been shown to have a positive influence on the eating quality of red meat. Selection of Australian lambs for increased lean tissue and reduced carcass fatness using Australian Sheep Breeding Values has been shown to decrease IMF% of the Muscularis longissimus lumborum. The impact this selection has on the IMF% of other muscle depots is unknown. This study examined IMF% in five different muscles from 400 lambs (M. longissimus lumborum, Muscularis semimembranosus, Muscularis semitendinosus, Muscularis supraspinatus, Muscularis infraspinatus). The sires of these lambs had a broad range in carcass breeding values for post-weaning weight, eye muscle depth and fat depth over the 12th rib (c-site fat depth). Results showed IMF% to be highest in the M. supraspinatus (4.87±0.1, P<0.01) and lowest in the M. semimembranosus (3.58±0.1, P<0.01). Hot carcass weight was positively associated with IMF% of all muscles. Selection for decreasing c-site fat depth reduced IMF% in the M. longissimus lumborum, M. semimembranosus and M. semitendinosus. Higher breeding values for post-weaning weight and eye muscle depth increased and decreased IMF%, respectively, but only in the lambs born as multiples and raised as singles. For each per cent increase in lean meat yield percentage (LMY%), there was a reduction in IMF% of 0.16 in all five muscles examined. Given the drive within the lamb industry to improve LMY%, our results indicate the importance of continued monitoring of IMF% throughout the different carcass regions, given its importance for eating quality.

Proteolytic changes of myofibrillar proteins in Podolian meat during aging: focusing on tenderness.

The aim of this study was to understand the relationship between changes in postmortem degradation of myofibrillar proteins and tenderness development in 3 different muscles from 10 Podolian young bulls aged 1, 7, 14, and 21 d. Psoas major (PM), longissimus dorsi (LD), and semitendinosus muscle () were removed from each half carcass 24 h postmortem. Meat chemical composition, Warner-Bratzler shear force (WBSF), myofibril fragmentation index (MFI), total collagen content, and changes in myofibrillar proteins were estimated in triplicate at each aging time. A significant muscle effect was found on meat chemical composition. Semitendinosus muscle showed the lowest intramuscular fat percentage ( < 0.01) and the highest total collagen content ( < 0.01) with respect to LD and PM. Warner-Bratzler shear force decreased during aging in all muscles ( < 0.001), and semitendinosus was the toughest muscle whereas PM was the most tender ( < 0.001). Myofibril fragmentation index significantly increased ( < 0.001) in LD and PM meat throughout aging time whereas in semitendinosus it increased from 14 d of aging. Proteolysis was investigated by SDS-PAGE, western blotting, and 2-dimensional electrophoresis. Throughout postmortem aging, some structural proteins changed in intensity in all muscles analyzed. The blotting profile highlighted that desmin and troponin-T (TnT) bands were affected by both muscle and aging effects. Desmin degradation was more intense and faster in LD muscle than in semitendinosus and PM muscles. A progressive increase of the degraded isoforms of TnT (33 and 30 kDa polypeptides) was found during aging in LD, while, in PM these bands appeared earlier showing a greater intensity from 1 d. During aging, 2-dimensional gel electrophoresis (2DE) image analyses results showed a significant increase of the total number of spots reaching the highest value in the LD muscle at 21 d of aging ( < 0.01). Proteins separation also revealed differences in the spot number and expression patterns of myosin light chain (MLC) isoforms among muscles. A principal components analysis applied to meat chemical composition, tenderness, and myofibrillar proteins accounted for approximately 96.09% of total variance. Data highlight that aging affects the meat tenderness and proteolysis with different intensities in each muscle. These results provide knowledge about the tenderness mechanism in different muscles from a rustic breed and could be useful for the development of muscle specific strategies for improving the quality and value in different commercial cuts.

The correlation of intramuscular fat content between muscles of the lamb carcass and the use of computed tomography to predict intramuscular fat percentage in lambs

Intramuscular fat (IMF) % contributes positively to the juiciness and flavour of lamb and is therefore a useful indicator of eating quality. A rapid, non-destructive method of IMF determination like computed tomography (CT) would enable pre-sorting of carcasses based on IMF% and potential eating quality. Given the loin muscle (longissimus lumborum) is easy to sample, a single measurement at this site would be useful, providing is correlates well to other muscles. To determine the ability of CT to predict IMF%, this study used 400 animals and examined 5 muscles from three sections of the carcass: from the fore-section the m. supraspinatus and m. infraspinatus, from the saddle-section the m. longissimus lumborum and from the hind-section the m. semimembranosus and m. semitendinosus. The average CT pixel density of muscle was negatively associated with IMF% and can be used to predict IMF% although precision in this study was poor. The ability of CT to predict IMF% was greatest in the m. longissimus lumborum (slope −0.07) and smallest in the m. infraspinatus (slope −0.02). The correlation coefficients of IMF% between the five muscles were variable, with the highest correlation coefficients evident between muscles of the fore section (0.67 between the m. supraspinatus and the m. infraspinatus) and the weakest correlations were between the muscle of the fore and hind section. The correlation between the m. longissimus lumborum to the other muscles was fairly consistent with values ranging between 0.34 and 0.40 (partial correlation coefficient). The correlation between the proportion of carcass fat and the IMF% of the five muscles varied and was greatest in the m. longissimus lumborum (0.41).

Spirulina Supplementation, Sire Breed, Sex and Basal Diet Effects on Lamb Intramuscular Fat Percentage and Fat Melting Points

The effects of Spirulina supplementation, sire breed, sex and basal diet on intramuscular fat percentage (IMF) and fat melting point (FMP) in crossbred and purebred Merino lambs were investigated. Over two consecutive years, a total of 48 lambs was randomly allocated into feeding trials that utilised either ryegrass or Lucerne hay basal diets. Each treatment group had 8 lambs balanced by sire breed (Black Suffolk, Dorset, Merino, White Suffolk), sex (ewes, wethers), and Spirulina supplementation level (CONTROL - unsupplemented, LOW 50ml, MEDIUM – 100ml, and HIGH – 200ml). Each feeding trial lasted for 9-weeks after 21 days of adjustment. Post-slaughter, IMF content of the Longissimus dorsi et lumborum muscle was determined using solvent extraction and FMP measured using the ‘slip-point’ method. Spirulina supplementation level influenced both IMF content and FMP in which MEDIUM Spirulina supplementation led to a decrease in IMF (1.98%) and FMP (42.97°C) compared to 3.18% and 44.44°C, respectively, in the LOW supplementation treatment group. Sire breed was a significant source of variation in FMP as purebred Merinos had the highest (45.63°C) and Black Suffolk crossbreds the lowest (41.53°C). Ewe lambs had higher IMF than wether lambs (2.52 vs 2.12%). Lambs on the ryegrass basal diet had lower IMF and FMP than their counterparts on Lucerne. Significant interactions between sire breed and supplementation level suggest a variety of nutritional management combinations that prime lamb producers can utilise to optimise meat quality for increasingly health-conscious consumers.