K.L. Pearce

Water distribution and mobility in meat during the conversion of muscle to meat and ageing and the impacts on fresh meat quality attributes — A review

This paper reviews current knowledge on the distribution and mobility of water in muscle (myowater) ante- and post mortem and factors affecting these in relation to fresh meat quality parameters; water-holding capacity (WHC), tenderness and juiciness. NMR transverse relaxometry (T(2)) using bench-top Low-Field Nuclear Magnetic Resonance (LF-NMR) has characterised myowater distribution and mobility as well as structural features in meat which directly affect WHC. The current literature demonstrates that WHC is correlated to the water located outside the myofibrillar network (extra-myofibrillar). This review identifies the critical stages which affect the translocation of water into the extra-myofibrillar space and thus the potential for decreased WHC during proteolysis (the conversion of muscle to meat). This review discusses how the intrinsic properties of the water held within the meat could contribute to juiciness and tenderness. Tenderness has been shown to correlate to T(2), however breed and species differences made it difficult to draw firm conclusions. Further understanding of the inherent water properties of fresh meat and the factors affecting water distribution and mobility using NMR technologies will increase the understanding of WHC and tenderisation of fresh meat.

Feed intake and production in sheep fed diets high in sodium and potassium

Salinity is a problem facing many crop and livestock producers in southern Australia. One management option is to revegetate with salt-tolerant plants suitable for animal production. These plants are often halophytic shrubs containing up to 30% ash, predominantly as sodium, potassium, or chloride. This experiment examines the consequences of a high intake of sodium and potassium separately or together on feed intake, digestibility, liveweight change, and wool growth. Twelve groups of 6 weaner wethers were allocated to treatments according to a balanced 3 × 4 factorial design with 3 levels of added potassium (0, 0.38, and 0.77 mol/kg DM equivalent to 0, 15, and 30 g/kg DM) and 4 levels of added sodium (0, 0.87, 2.18, and 3.48 mol/kg DM, equivalent to 0, 20, 50, and 80 g/kg DM) as the chloride salts. The treatment diets were fed to sheep for 6 weeks. Increasing sodium in the diet significantly decreased feed intake, digestibility, liveweight gain, and wool growth either as a main effect or through an interaction with potassium. Organic matter intake was reduced from 1.35 kg at the lowest levels of sodium and potassium to 0.67 kg at the highest levels. Comparing the same 2 groups, liveweight gain was reduced from 144 to 0 g/day, organic matter digestibility from 59.1% to 57.3%, and wool growth from 1.21 to 1.04 mg/cm 2 .day. The response surfaces indicate that production was depressed even at the lower levels of sodium, whereas high potassium depressed intake, digestibility, and liveweight gain at high levels of sodium only. The interaction between sodium and potassium was always negative at high levels of sodium, indicating that manipulation of the proportions of the 2 elements is unlikely to provide benefits for animal production when total salt levels are high. Although wool growth was depressed at high sodium and potassium, the efficiency of wool growth increased from 10.0 to 15.4 g/kg organic matter intake when the lowest and highest levels of the sodium and potassium were compared. This result may present significant opportunities for the use of saline land to grow fine wool.

Genetic parameters for meat quality traits of Australian lamb meat

Genetic parameters were estimated for a range of meat quality traits recorded on Australian lamb meat. Data were collected from Merino and crossbred progeny of Merino, terminal and maternal meat breed sires of the Information Nucleus programme. Lambs born between 2007 and 2010 (n=8968) were slaughtered, these being the progeny of 372 sires and 5309 dams. Meat quality traits were found generally to be of moderate heritability (estimates between 0.15 and 0.30 for measures of meat tenderness, meat colour, polyunsaturated fat content, mineral content and muscle oxidative capacity), with notable exceptions of intramuscular fat (0.48), ultimate pH (0.08) and fresh meat colour a* (0.08) and b* (0.10) values. Genetic correlations between hot carcass weight and the meat quality traits were low. The genetic correlation between intramuscular fat and shear force was high (-0.62). Several measures of meat quality (fresh meat redness, retail meat redness, retail oxy/met value and iron content) appear to have potential for inclusion in meat sheep breeding objectives.

Quality of lamb meat from the Information Nucleus Flock.

The effects of production and processing factors on tenderness, and colour of lamb meat produced from 7 locations as part of the Australian Sheep Industry CRCs Information Nucleus flock were investigated, using data from 2052 lambs slaughtered in 2007. At 24 h post-slaughter, samples of m. longissimus lumborum(LL) and m. semimembranosus (SM) were collected for measurement of intramuscular fat (IMF), myoglobin, iron and copper and fresh meat colour (L*, a*, b*) and pH at 24 h measured on the LL. pH and temperature measurements made pre-rigor were used to calculate the pH at 18 degrees C. Tenderness was measured by LL shear force at days 1 (SF1) and 5 (SF5) post-slaughter, the shear force difference (SF-diff) and SM compression and collagen concentration were determined. Retail colour stability was assessed using over-wrapped LL under simulated retail display for 3 days, according to the change in the oxymyoglobin/metmyoglobin ratio. All traits were affected by flock and date of slaughter (P < 0.001). After 4 days of ageing, 70-95% of the LL samples from all flocks, except for one, had acceptable tenderness for consumers based on their shear force. Low IMF, high LL pH at 18 degrees C and high pH at 24 h increased SF1 and SF5 and also had an effect on SF-diff (P<0.001). The retail colour of 44.8% of the samples on day 3 of retail display were lower than acceptable. Retail colour was influenced by IMF, pH18 and the concentration of iron and copper (P < 0.001). In conclusion, breeding and management practices that increase muscle IMF levels and reduce ultimate pH values and processing practices that result in moderate rates of pH fall post-slaughter, improve the tenderness of lamb. Extension of retail colour stability may be antagonistic to traits associated with tenderness and nutritional traits, particularly IMF and mineral levels.

Preliminary estimates of genetic parameters for carcass and meat quality traits in Australian sheep.

Using performance from progeny born in 2007 and 2008 generated by theInformation Nucleus program of the Cooperative Research Centre for Sheep Industry Innovation, preliminary estimates of heritability were obtained for a rangeofnovelcarcassandmeatattributesoflambrelevanttoconsumers,includingcarcasscharacteristics,meatqualityand nutritionalvalueoflamb.Phenotypicandgeneticcorrelationsofliveanimaltraitswithcarcasscompositionandmeatquality traits were also estimated. The data were from progeny located at eight sites, sired by 183 rams from Merino, maternal and terminalmeatbreedsandwererepresentative oftheMerino,BorderLeicester ·Merino,Terminal ·MerinoandTerminal · Border Leicester-Merino production types of the Australian sheep industry. Data were available from 7176 lambs for weaning weight, 6771 lambs for ultrasound scanning and 4110 lambs for slaughter traits. For the novel meat quality traits, generally moderate to high heritability estimates were obtained for meat quality measures of shear force (0.27 aged 1 day, 0.38 aged 5 days), intramuscular fat (0.39), retail meat colour (range of 0.09 to 0.44) and myoglobin content (0.22). The nutritional value traits of omega-3 fatty acids and iron and zinc contents tended to have low to moderate heritabilities (0.11-0.37), although these were based on fewer records. Fresh meat colour traits were of low to moderate heritability (0.06-0.21)whereasmeasuresofmeatpHwereoflowheritability(~0.10).Forthecarcasstraits,estimatesofheritabilitywere moderate to high for the various measures of carcass fat (0.18-0.50), muscle weight (0.22-0.35), meat yield (0.24-0.35), carcassmuscledimensions(0.25-0.34)andboneweight(0.27).Resultsindicatethatformostlambcarcassandmeatquality traits there is sufficient genetic variation for selection to alter successfully these characteristics. Additionally, most genetic correlations of live animal assessments of bodyweight, muscle and subcutaneousfat with the carcass and meat quality traits werefavourable.Appropriatedefinitionofbreedingobjectivesanddesignofselectionindexesshouldbeabletoaccountfor the small unfavourable relationships that exist and achieve the desired outcomes from breeding programs.

Associations of sire estimated breeding values and objective meat quality measurements with sensory scores in Australian lamb

The impact of selecting for lean meat yield using breeding values for increased eye muscle depth (PEMD) and decreased fat depth (PFAT) on the consumer acceptance of lamb meat was evaluated. Consumer sensory scores (tenderness, juiciness, flavour, odour, overall liking) were obtained for the longissimus lumborum (loin) and semimembranosus (topside) muscles of 1471 lambs. On average loin samples were more acceptable for consumers. Sensory scores increased with higher IMF levels, with lower shear force levels, and when animals were younger and less muscular. Increasing PEMD decreased tenderness, overall liking and flavour scores in both muscles, and decreasing PFAT reduced tenderness within the loin samples only. This negative impact of PEMD and PFAT is not solely driven through the phenotypic impact of IMF and shear force on sensory scores. Our results confirm the growing concerns that selecting for lean meat yield would reduce consumer eating quality, and highlight that careful monitoring of selection programmes is needed to maintain lamb eating quality.

Plasma and tissue α-tocopherol concentrations and meat colour stability in sheep grazing saltbush (Atriplex spp.)

Dry senesced pastures available during the summer and autumn period in Western Australia and other areas with a Mediterranean climate are low in vitamin E. The use of expensive and labour-intensive supplements to prevent nutritional myopathy induced by vitamin E deficiency in weaner sheep is common. Low vitamin E concentrations in the muscle preslaughter can also reduce the shelf life of meat. There is growing interest in incorporating saltbush into farming systems in Western Australia. The potential for saltbush to boost the vitamin E status of sheep and improve the shelf life of meat was investigated. Fifty (2 × 25) 18-month-old Merino hogget wethers (average liveweight 48 kg) were grazed on either a saltbush-dominant saline pasture or on a ‘control’ dry pasture, stubble plot for 14 weeks. At the start of the experiment, all animals were orally supplemented with 2500 IU of dl-α-tocopherol acetate in 6.25 mL solution. The α-tocopherol content in saltbush was 139 and 116 mg/kg dry matter for old man and river saltbush, respectively. Concentrations of α-tocopherol were measured in plasma at Weeks 0, 4, 8, and 12 and in muscle and liver samples taken at slaughter. Grazing on saltbush significantly elevated α-tocopherol concentrations in the liver and muscle compared with grazing on dry pasture, well above the threshold for vitamin E inadequacy (P < 0.001). Plasma α-tocopherol concentrations in sheep fed saltbush increased up to Week 8 and then decreased until the end of the experiment as availability of saltbush declined (P < 0.05). Plasma α-tocopherol in sheep fed dry pasture increased in the first 4 weeks due to the initial vitamin E treatment but declined thereafter, indicating that the pasture was low in vitamin E. The high muscle concentrations of α-tocopherol in sheep fed saltbush also improved colour stability and may have had an influence on drip and cooking loss. The meat from the saltbush-grazed sheep was moister but drip and cooking loss was the same as from the drier meat of the control sheep. In conclusion, this study demonstrates that saltbush is a potential vitamin E source for sheep.

Case studies demonstrating the benefits on pH and temperature decline of optimising medium-voltage electrical stimulation of lamb carcasses

The efficacies of electrical stimulation practices at Australian abattoirs that process significant proportions of Australianlambandsheepmeatwereassessed.Severalabattoirsusedmedium-voltageelectricalstimulationsystem(MVS) units suboptimally and many carcasses at these abattoirs exhibited a poor rate of pH decline and, consequently, a low proportion of carcasses attained pH 6 at a carcass temperature of 1835C, according to Sheep Meat Eating Quality pH-temperatureguidelinesasadoptedbyMeatStandardsAustralia.Inthepresentcommunication,wedescribethecausesof suboptimal results withelectrical stimulation and discussprocedures for optimising thestimulation dose delivered by MVS units.CarcasspHresponsestovariouslevelsofcurrentandpulsewidthwereassessedtodeterminethebestMVSsettingsfor individual abattoirs. The MVS units at the abattoirs involved in the present study have now been programmed for optimal efficacy and carcass quality will be monitored on an ongoing basis. Evaluation of methods for assessing the proportion of carcassesthatfallwithintheoptimumpH-temperaturewindowshowedthatarandomregressionmodelismoreaccuratethan the current approach.

Using Australian Sheep Breeding Values to increase lean meat yield percentage

This study describes the impact of Australian Sheep Breeding Values (ASBV) for post-weaning weight (PWWT), C-site fatness (PFAT) and eye muscle depth (PEMD) on lamb carcasses within the Australian Sheep Industry CRC Information Nucleus Flock. These results are taken from the 2007 drop progeny, consisting of ~2000 lambs slaughtered at a target weight of 21.5 kg. These lambs were the progeny of sires selected to ensure genetic diversity across various production traits. As expected, the PWWT ASBV increased weight at slaughter, and hot standard carcass weight. Dressing percentage was markedly improved by increasing PEMD ASBV, thus prime lamb producers will be maintaining an animal of similar weight on farm, but delivering a markedly larger carcass at slaughter. Lean meat yield % (LMY%) was highest in the progeny of sires with low PFAT ASBV, which decreased whole carcass fatness and increased muscularity. PWWT ASBV affected carcass composition but had little impact on LMY%, as the decreased fatness was largely offset by increased bone, with relatively little change in muscle content. Lastly, PEMD ASBV had little impact on whole carcass LMY%, but did appear to cause some level of muscle redistribution to the higher value loin cuts, in turn increasing the value of the carcass lean.

Dual X-ray absorptiometry accurately predicts carcass composition from live sheep and chemical composition of live and dead sheep

Fifty merino wethers (liveweight range from 44 to 81kg, average of 58.6kg) were lot fed for 42d and scanned through a dual X-ray absorptiometry (DXA) as both a live animal and whole carcass (carcass weight range from 15 to 32kg, average of 22.9kg) producing measures of total tissue, lean, fat and bone content. The carcasses were subsequently boned out into saleable cuts and the weights and yield of boned out muscle, fat and bone recorded. The relationship between chemical lean (protein+water) was highly correlated with DXA carcass lean (r(2)=0.90, RSD=0.674kg) and moderately with DXA live lean (r(2)=0.72, RSD=1.05kg). The relationship between the chemical fat was moderately correlated with DXA carcass fat (r(2)=0.86, RSD=0.42kg) and DXA live fat (r(2)=0.70, RSD=0.71kg). DXA carcass and live animal bone was not well correlated with chemical ash (both r(2)=0.38, RSD=0.3). DXA carcass lean was moderately well predicted from DXA live lean with the inclusion of bodyweight in the regression (r(2)=0.82, RSD=0.87kg). DXA carcass fat was well predicted from DXA live fat (r(2)=0.86, RSD=0.54kg). DXA carcass lean and DXA carcass fat with the inclusion of carcass weight in the regression significantly predicted boned out muscle (r(2)=0.97, RSD=0.32kg) and fat weight, respectively (r(2)=0.92, RSD=0.34kg). The use of DXA live lean and DXA live fat with the inclusion of bodyweight to predict boned out muscle (r(2)=0.83, RSD=0.75kg) and fat (r(2)=0.86, RSD=0.46kg) weight, respectively, was moderate. The use of DXA carcass and live lean and fat to predict boned out muscle and fat yield was not correlated as weight. The future for the DXA will exist in the determination of body composition in live animals and carcasses in research experiments but there is potential for the DXA to be used as an online carcass grading system.