Differences in composition, muscularity, muscle:bone ratio and cut dimensions between six lamb genotypes

Carcass measurements and composition data were obtained for 198 lambs representing two sexes (104 cryptorchids, 94 ewes). Dorsal images of 166 of the carcasses were obtained on the slaughter chain using a video camera. The lambs were sired by a selection of Poll Dorset (PD), Texel (T), Border Leicester (BL) and Merino (M) rams, born to Border Leicester × Merino (BLM) and Merino (M) ewes giving 6 genotypes (PD × BLM, T × BLM, PD × M, T × M, BL × M, M × M). From the right hindleg and chump, the following muscles were dissected and weighed: semimembranosus, adductor femoris, semitendinosus, biceps femoris, and quadriceps femoris. The femur was weighed, the length measured and a muscularity value calculated as described by Purchas, et al. (1991, Meat Sci., 30, 181).

Merino cryptorchid lambs were significantly (P < 0.05) leaner, as measured by GR tissue depth (for explanation, see MATERIALS AND METHODS) adjusted to a mean carcass weight of 24.2 kg, than BL × M lambs, but there was no difference between genotypes within the ewe group (mean carcass weight of 17.1 kg). Genotype differences were found for conformation using the EUROP scoring system. Merino lambs had a greater proportion (P < 0.001) of poorer scores, particularly compared to PD × BLM and T × BLM carcasses. The BL × M carcasses had a significantly (P < 0.05) smaller m. longissimus thoracis et lumborum area than other genotypes with no difference between carcasses of T and PD sires.

Muscularity values for the BL × M and M lambs were significantly (P < 0.05) lower than the other crosses but not different from each other. Carcasses from T sires had significantly (P < 0.05) higher muscularity values than those from PD sires. A negative association (r = −0.56) was found between EUROP scores and muscularity when carcass differences were adjusted for, but significant differences between genotypes for muscularity were not necessarily carried through to differences in EUROP conformation score. BL × M carcasses had the lowest muscle:bone ratio and T × M the highest with M carcasses having similar ratios to carcasses from PD-sired lambs. Only small differences were found between genotypes for composition of the hindleg, the exception being BL × M carcasses of both sexes which were significantly (P < 0.05) fatter than T × BLM, T × M and PD × M carcasses. Carcasses from T sires had significantly (P < 0.05) more muscle in the hindleg than carcasses from PD sires, with the differences being greater in the heavier cryptorchids (1.8%) than the ewes (1.1%). There was no consistent effect of genotype on the cross-sectional areas of the round and topside cuts within either sex.

Differences between genotypes for the proportion of the carcass attributed to the round were small and only for BL × M ewe carcasses was this cut significantly lighter (P < 0.05) than from all other genotypes, except the PD × BLM carcasses. This trend was similar for the topside and silverside cuts. A moderate correlation (r = 0.46; P < 0.001) was found between muscularity values determined by dissection and those predicted using the equations of Hopkins et al. (1996, Proc. Aust. Soc. Anim. Prod., 21, 181) based on carcass width measurements taken from video images.     

A note on the muscle, fat and bone contents of Portuguese light lamb carcasses

A total of 72 lambs weighing between 10.1-13.0 kg (category C of the European Union grading for light lambs) from the Bragan?ano, Campani?o, Merino Branco, Merino Preto e Serra da Estrela breeds were studied. These breeds represent 66.8% of the Portuguese sheep population. Evaluations were made at the same subcutaneous fat contents in the carcass (88.5 g kg(-1)). Small, significant (p < 0.05) differences in the range of muscle and bone contents were found; the ranges being 30 and 25 g kg(-1), respectively. These variations led to significant diferences in the muscle:bone ratios, the highest value being 3.30 and the lowest 2.73. Significant differences were also found in the content of higher-priced joints (leg + chump, loin + ribs and anterior ribs) and in the proportion of kkcf (9 g kg(-1)). No significant differences were found in the content of total fat [subcutaneous, intermuscular and kidney knob and channel fat (kkcf)] and in the muscle: total fat ratios.     

Video image analysis in the Australian meat industry - precision and accuracy of predicting lean meat yield in lamb carcasses

A wide selection of lamb types of mixed sex (ewes and wethers) were slaughtered at a commercial abattoir and during this process images of 360 carcasses were obtained online using the VIAScan? system developed by Meat and Livestock Australia. Soft tissue depth at the GR site (thickness of tissue over the 12th rib 110 mm from the midline) was measured by an abattoir employee using the AUS-MEAT sheep probe (PGR). Another measure of this thickness was taken in the chiller using a GR knife (NGR). Each carcass was subsequently broken down to a range of trimmed boneless retail cuts and the lean meat yield determined. The current industry model for predicting meat yield uses hot carcass weight (HCW) and tissue depth at the GR site. A low level of accuracy and precision was found when HCW and PGR were used to predict lean meat yield (R(2)=0.19, r.s.d.=2.80%), which could be improved markedly when PGR was replaced by NGR (R(2)=0.41, r.s.d.=2.39%). If the GR measures were replaced by 8 VIAScan? measures then greater prediction accuracy could be achieved (R(2)=0.52, r.s.d.=2.17%). A similar result was achieved when the model was based on principal components (PCs) computed from the 8 VIAScan? measures (R(2)=0.52, r.s.d.=2.17%). The use of PCs also improved the stability of the model compared to a regression model based on HCW and NGR. The transportability of the models was tested by randomly dividing the data set and comparing coefficients and the level of accuracy and precision. Those models based on PCs were superior to those based on regression. It is demonstrated that with the appropriate modeling the VIAScan? system offers a workable method for predicting lean meat yield automatically.     

Usefulness of various biochemical and histochemical characteristics as indices of muscle type in lamb carcasses

Contractile and metabolic characteristics of five different muscles from an homogeneous group of seven lambs were studied. Muscle typing was assessed by measuring myofibrillar ATPase and lactate deshydrogenase activities, myosin (FM1, FM2, FM3, SM1, SM2) and LDH (M₄, M₃H, M₂H₂, MH₃, H₄) isoforms levels as well as fibre types composition (SO, SOG, FOG, FG). On this basis, muscles were classified as slow-twitch oxidative (diaphragm and supraspinatus), intermediate (triceps brachii), fast-twitch oxidative-glycolytic (longissimus dorsi) and fast-twitch glycolytic (tensor fascia latae). Discriminant factor analysis of data revealed that variables enabling a better discrimination of muscles (FG, SM1, FM2, FM1, H₄) exhibited the lowest efficiency to discrimate animals. Furthermore, in contrast to LDH isoforms and fibre type composition subsets of variables, myosin isoforms analysis allowed a quite total identification of muscle classes since, 97·5% of the muscles were well ranged in their respective classes. Although animals were zootechnically similar, animal variability was important and animal effect was essentially detected through changes in the following set of variables: M₃H, MH₃, SO and ATPase.     

Composition and sensory evaluation of lamb carcasses used for the traditional Mexican lamb dish, "barbacoa"

The objective of this study was to determine the differences in carcass characteristics and sensory attributes of "barbacoa" (a traditional Mexican lamb dish), both of imported (New Zealand) and domestic lambs in Mexico. A total of 28 carcasses from Pelibuey, Pelibuey×Suffolk and imported lambs were used. Carcass composition was determined by dissection of primal cuts from the left half of each carcass. The "barbacoa" from each ovine group was prepared separately in order to perform a consumer sensory evaluation for aroma, taste and tenderness. Results showed that imported lambs had larger carcasses, greater fatness and had better conformation than national lambs. There was no difference between groups in terms of lean tissue percentage (muscle+others) or in total carcass fat. The sensory attributes of the "barbacoa" did not differ among breeds. Pelibuey lambs (rustic, prolific and adaptable to the wide variety of Mexican climates) show competitive production performance in relation to specialized breeds.     

Prediction of fat, muscle and value in Norwegian lamb carcasses using EUROP classification, carcass shape and length measurements, visible light reflectance and computer tomography (CT)

One hundred and twenty carcasses were sampled to compare different techniques or methods for prediction of lamb carcass composition and value. Four methods that are used at the Norwegian Meat Research Centre, Animalia, were selected. These were the basic EUROP classification, the advanced EUROP classification using carcass shape and length measurements, visible light reflectance probing (GP) and Computer Tomography (CT). The different technologies were tested using an iterative approach, selecting calibration and validation data sets from the 120 carcasses randomly, where 90 carcasses were used for calibration, and 30 for validation. The best prediction models were obtained using CT, with respect to prediction error and correlation between predicted and measured value of carcass fat and muscle (in kg), and value (in NOK). Due to high cost and low operating speeds of CT, optical probing (GP) may be the second best solution of the technologies used in this study, combined with a CT dissection reference as an alternative to manual dissection.     

Diverse lamb genotypes. 3. Eating quality and the relationship between its objective measurement and sensory assessment

The effect of genotype on eating quality was evaluated on m. Longissimus thoracis et lumborum (LTL) muscle of 60 lambs. The lambs were sired by a selection of Texel (T), Poll Dorset (PD), Border Leicester (BL) and Merino (M) rams, crossed with Border Leicester x Merino (BLM) and Merino (M) ewes giving six genotypes (TxBLM, PDxBLM, TxM, PDxM, BLxM and MxM). The relationships between sensory panel assessment of eating quality attributes and pH, cooking loss and shear force were also investigated. No significant differences were observed between genotypes for panel assessment of tenderness, juiciness, aroma liking, aroma strength, flavour liking, overall acceptability and rating. MxM lambs had a significantly (P<0.05) higher flavour strength than BLxM lambs. pH was a poor indicator of any eating quality attributes, except aroma strength (r=0.3, P<0.05). Warner Bratzler shear force value (WB) and tenderness showed a significant (P<0.001) negative correlation (-0.7). Tenderness, flavour and juiciness were the most important sensory attributes, explaining 86.5% of the total variation in overall acceptability.     

Genetic analysis of male and female fertility using longitudinal binary data

A longitudinal Bayesian threshold analysis of insemination events during the first 250 d after calving of first-parity Holsteins was carried out. The outcome of an insemination event was treated as a binary response of either a success (1) or a failure (0). Thus, all breeding information for a cow, including all service sires, was included, thereby allowing for a joint evaluation of male and female fertility. An edited data set of 297,823 insemination records from 151,758 first lactation cows was used. On the liability scale, the model included the systematic effects of herd-year of insemination, technician, month of insemination, and regressions on age of service sire, 3 test days in the first 100 d of lactation (early milk yield), and days in milk at insemination. The random effects in the model were the additive breeding value, the permanent effect of the cow, and the service sire effect. Posterior mean (standard deviation) of the dispersion parameters in the model were 0.034 (0.006), 0.009 (0.001), and 0.171 (0.013) for the additive, service sire, and permanent environmental variances, respectively. The residual variance was fixed at 1, as a result of the nonidentifiability of the threshold model. The posterior mean (standard deviation) of heritability was 0.028 (0.005). This point estimate of heritability is well within the range of available estimates for the trait. Thus, these estimates suggest that some genetic variation exists that can potentially be used to improve reproductive performance or at least avoid its further deterioration. The estimate of the regression coefficient on age of service sire was 0.001, indicating better fertility among older bulls. However, this result has to be interpreted with caution given the preferential use of proven bulls on well-managed cows (as opposed to problem breeders). The estimate of the regression coefficient was negative (-0.005) for early milk yield, as expected, and positive (0.003) for days in milk at insemination. This suggests that high-producing cows are less likely to conceive at the beginning of lactation.     

The relationship between conformation and the yield and distribution of lean meat in the carcasses of British pigs, cattle and sheep: A review

Information available on the value of conformation as a predictor of carcass composition in the British livestock population is reviewed, particular reference being made to recent Meat and Livestock Commission (MLC) trials using the visual conformation assessments employed in national carcass classification schemes. In mixed breed populations, the visual conformation assessments are positively related to lean to bone ratio and muscle thickness, although the correlations are generally low. Their relationship with carcass lean content depends on the effectiveness with which variation in fatness is eliminated since fatter carcasses tend to be given higher conformation scores. Conformation provides little information about the proportion of total lean occurring in the higher priced joints. The value of conformation in a mixed breed population depends to an important extent on its ability to identify breed differences in carcass characteristics. Although of some value in this respect, it is less effective than actual breed identification. Within-breed regressions on conformation are generally in the same direction as those in the mixed breed populations, although the precision of prediction is lower. The results indicate that conformation has little practical value as a predictor of carcass composition within breed.     

Predicting the weight of lean meat in lamb carcasses and the suitability of this characteristic as a basis for valuing carcasses

The carcasses of 138 lambs were dissected into fat, muscle and bone as the basis for developing a model to estimate the weight of lean meat (muscle and intramuscular fat). The lambs represented two sexes (70 wethers, 68 ewes) and three sire genotypes (67 Poll Dorset, 39 Suffolk, 32 Wiltshire Horn) all from Border Leicester × Polwarth × Booroola type ewes. Hot carcass weight (HWT) was found to explain the majority of the variation in the weight of lean meat. When measures of subcutaneous fat depth at different sites were used as predictors in addition to HWT, the accuracy with which lean meat yield could be estimated was found to increase by a small amount. There was, however, little difference in their individual value as predictors. The area of the M. longissimus thoracis et lumborum at the twelfth-thirteenth rib was found to account for the significant breed type difference between Poll Dorset and Suffolk sired lambs when included in a multiple regression with HWT and the GR measurement (tissue thickness at the twelfth rib 110 mm from the midline). The final model produced an R(2) = 0·92 and an RSD = 0·45 kg for the 106 lambs. Using the model for the 106 lambs, the estimated (from the model) and actual values of lean meat for the Wiltshire Horn sired lambs were compared. The correlation coefficient between the values was r = 0·97 and the RSD was 0·31 kg. This shows that for second cross lambs as used in this study the fitted model exhibits a degree of general validity and stability. An overall model for the 138 lambs produced an R(2) = 0·92 an RSD = 0·43 kg. The potential for pricing meat on the basis of lean meat yield is discussed, with particular emphasis on the current developments in assessment of lamb carcasses in Australia.     

The relationship between tenderness, proteolysis, muscle contraction and dissociation of actomyosin

The right side m. longmissius thoracis et lumborum (LTL) of 18 10-month-old male lambs was injected with the protease inhibitor E-64, and the left side was injected with isotonic saline within 30 min of stunning. Carcasses were hung during chilling by one of three methods; Achilles tendon; pubic symphysis or pubic symphysis with 2-kg weights attached to each hindleg. The LTL section was divided into three portions and aged for either 1, 3 or 7 days. The tenderness, myofibrillar fragmentation and dissociation of extracted actomyosin by pyrophosphate were determined for each portion of LTL. The protease inhibitor increased shear force values by 57%, with a decrease in shear force in the cranial-caudal direction along the LTL. Muscle from Achilles hung carcasses was the toughest. For sarcomere length hanging method had the greatest effect, with muscle from tenderstretched/weighted carcasses having the longest sarcomeres. Injection of an inhibitor caused a significant reduction in myofibrillar fragmentation (P< 0.001) and hanging method and ageing period also significantly affected this characteristic (P< 0.05). Osmolality of samples aged for 1 day was unaffected by any main effect. The amount of actomyosin (mg/g of muscle sample) extracted from muscles injected with the inhibitor was significantly less (P< 0.001) and there was also a significant effect (P< 0.05) of portion on this variable. The relationship between pyrophosphate and the percentage of myosin dissociated from the actomyosin complex was modelled using an exponential function; Y=A - B exp(-kx). Analysis of A, B and k for the 69 samples fitted with an exponential function showed that there was no significant effect (P>0.05) on A and k of any main effect or their interactions. There was, however, a significant effect (P<0.05) of portion on B and also a significant interaction between injection and hanging method (P<0.05). It was found that B did not explain any additional variance in shear force or myofibrillar fragmentation over the main effects and interactions previously found significant. The inhibitor E-64 was effective at preventing tenderisation indicating the role of cysteine proteases in proteolytic degradation. There was no apparent effect of dissociation on tenderness as measured in this experiment and therefore a causal relationship cannot be identified.     

A survey of pH values at the surface of beef and lamb carcasses,stored in a chiller

The surface pH values of lamb and beef carcasses stored at 5 ºC have been measured over a 5-day period. In both types of animal, muscle surfaces were at or near their minimum pH at 3 days, when the overall mean was pH 6.4. In the subsequent 2 days some sites showed no change in pH, while at others a small drop or a rise occurred. Rises in pH tended to be more common and greater on the beef. In lamb, intact muscle surfaces varied only from pH 6.3 to 6.6 at 3 days, while beef muscles varied widely, from pH 5.8 to 7.1. Muscle surfaces cut during dressing fell much more rapidly in pH, particularly in beef. Fatty sites fell from near pH 8.0 to near pH 7.0. The pH of beef surfaces chilled to -3 ºC fell more rapidly to lower final values than those at 5 ºC. At 5 ºC there was little multiplication of bacteria on fat surfaces, whereas on muscle they grew moderately, irrespective of pH.     

Estimation of the muscle to bone ratio of the bovine pelvic limb using a morphometric method

Conformation is an indicator of carcass composition. The aim of this study was to derive an equation for estimating the composition of the bovine pelvic limb using morphometric variates. From a mixed group of 38 French bred bovines, the sample was chosen to have a wide range of conformation. The muscle to bone ratio (M/B) was used as an index of composition. The carcasses were weighed and the other variates of the equation were measured on carcass photographs: M/B = 6.2 + 0.005W − 0.62EF/AB + 12GH with W: carcass weight (kg); GH: medio-lateral diameter of the distal part of the leg (cm); EF/AB: medio-lateral diameter of thigh (cm)/leg length(cm); (R² = 0.91 and RSD = 0.27).     

The relationship between the subjective and objective measurement of pork colour

Summary. The colour of ninety-seven pig longissimus dorsi muscles was measured using a spectrophotometer, a simple colour reflectometer, and an untrained panel of ten graders. the results obtained from the colour meters and the graders were compared with Munsell V value of the samples, calculated from the reflection spectra.
Visual colour grading produced a near linear correlation with the Munsell V value. Dark samples tended to be underestimated, whereas pale samples were overestimated by the panel. There was considerable variation between observers'scores, between methods of visual grading, and between visual and instrumental grading. Results obtained from the colour meter were reproducible. the error in comparison with the spectrophotometer was small. the colour meter provides a convenient portable and inexpensive method of measuring the colour lightness of pork muscle.
The experiment showed the practicability of objective measurement of meat colour lightness. the determination of colour quality, however, requires both subjective and objective measurements.     

Predicting the composition of lamb carcases using alternative fat and muscle depth measures

Hot carcase weight (HCW) and the GR tissue depth (total tissue depth over the 12th rib, 110 mm from the midline) were measured on 312 crossbred (Poll Dorset × Merino) lambs with a mean live weight of 47 kg. At a position 30 mm distal to the lumbar-sacral junction, the depth (RMD) of the rump muscles was measured along with subcutaneous fat depth overlaying the m. gluteus medius (RFD). The subcutaneous fat depth over the m. longissimus (loin) at the 12th rib was measured (Fat C), as was the depth and width of the loin cross section (EMD and EMW, respectively). The right side of each carcase was scanned by a dual energy X-ray bone densitometer and fat and lean weight determined and the percentage of lean and fat content in the carcases calculated. HCW alone accounted for 26% of the variation in percentage lean content (LC), with GR measurement being the single best predictor of LC (R² = 48.1; r.s.d. = 1.89). RFD provided a less accurate and precise estimate of LC (R² = 37.3; r.s.d. = 2.07) than either GR or Fat C (R² = 46.5; r.s.d. = 1.92). Inclusion of HCW with either GR or Fat C provided a small improvement in the amount of variation in LC which could be explained. The measurement of breeding animals by ultrasound includes the terms weight, Fat C and EMD. These predictors when combined explained 49% of the variation in LC whereas by comparison measures of weight, RFD and RMD only explained 42% of the variation in LC. The current method of measuring fat depth over the 12th/13th rib is practical and measurement over the rump does not present an advantage based on the results of this study.     

Pre-rigor temperature and the relationship between lamb tenderisation,free water production,bound water and dry matter

The M. longissimus from lambs electrically stimulated at 15 min post-mortem were removed after grading, wrapped in polythene film and held at 4 (n = 6), 7 (n = 6), 15 (n = 6, n = 8) and 35 °C (n = 6), until rigor mortis then aged at 15 °C for 0, 4, 24 and 72 h post-rigor. Centrifuged free water increased exponentially, and bound water, dry matter and shear force decreased exponentially over time. Decreases in shear force and increases in free water were closely related (r² = 0.52) and were unaffected by pre-rigor temperatures.     

我国教育机会均等的性别差距研究

研究表明,我国男女在受教育机会方面的差距在缩小,但农村、西部等不发达地区的女性教育并没有得到改善,甚至有的差距在扩大.这种不发达地区女性教育落后有其传统的原因,也有政策和经济的深层原因.不发达地区的女性作为教育机会均等当中弱势的弱势,值得长期关注.