A simple index that reflects the potential eating quality of beef carcasses is very important for producer feedback. The Meat Standards Australia (MSA) Index reflects variation in carcass quality due to factors that are influenced by producers (hot carcass weight, rib fat depth, hump height, marbling and ossification scores along with milk fed veal category, direct or saleyard consignment, hormonal growth promotant status and sex). In addition, processor impacts on meat quality are standardised so that the MSA Index could be compared across time, breed and geographical regions. Hence, the MSA Index was calculated using achilles hung carcasses, aged for 5 days postmortem. Muscle pH can be impacted by production, transport, lairage or processing factors, hence the MSA Index assumes a constant pH of 5.6 and loin temperature of 7°C for all carcasses. To quantify the cut weight distribution of the 39 MSA cuts in the carcass, 40 Angus steers were sourced from the low (n = 13), high (n = 15) and myostatin (n = 12) muscling selection lines. The left side of each carcass was processed down to the 39 trimmed MSA cuts. There was no difference in MSA cut distribution between the low and high muscling lines (P > 0.05), although there were differences with nine cuts from the myostatin line (P < 0.05). There was no difference in the MSA Index calculated using actual muscle percentages and using the average from the low and high muscling lines (R² = 0.99). Different cooking methods impacted via a constant offset between eating quality and carcass input traits (R² = 1). The MSA Index calculated for the four most commercially important cuts was highly related to the index calculated using all 39 MSA cuts (R² = 0.98), whilst the accuracy was lower for an index calculated using the striploin (R² = 0.82). Therefore, the MSA Index was calculated as the sum of the 39 eating quality scores predicted at 5 days ageing, based on their most common cooking method, weighted by the proportions of the individual cut relative to total weight of all cuts. The MSA Index provides producers with a tool to assess the impact of management and genetic changes on the predicted eating quality of the carcass. The MSA Index could also be utilised for benchmarking and to track eating quality trends at farm, supply chain, regional, state or national levels.

This study evaluated the effect of eye muscle area (EMA), ossification, carcass weight, marbling and rib fat depth on the incidence of dark cutting (pHᵤ>5.7) using routinely collected Meat Standards Australia (MSA) data. Data was obtained from 204,072 carcasses at a Western Australian processor between 2002 and 2008. Binomial data of pHᵤ compliance was analysed using a logit model in a Bayesian framework. Increasing eye muscle area from 40 to 80 cm², increased pHᵤ compliance by around 14% (P<0.001) in carcasses less than 350kg. As carcass weight increased from 150 kg to 220 kg, compliance increased by 13% (P<0.001) and younger cattle with lower ossification were also 7% more compliant (P<0.001). As rib fat depth increased from 0 to 20 mm, pHᵤ compliance increased by around 10% (P<0.001) yet marbling had no effect on dark cutting. Increasing musculature and growth combined with good nutrition will minimise dark cutting beef in Australia.

Dark cutting is detrimental to meat quality and therefore is the major cause of carcass downgrades under the Meat Standards Australia grading system. This study quantified the variation between months in the incidence of dark cutting, in southern Australia. Four years of Meat Standards Australia grading data, from nine individual beef processors in Western Australia, South Australia, Victoria and Tasmania, was utilised for the analysis. The dataset contained 42 162 slaughter groups, of 10 or more grass-fed cattle, which allowed for the percentage of dark cutters per slaughter group to be analysed. The interaction between month, year and state was significant (P<0.001). The lowest risk of dark cutting for South Australia and Western Australia was in October (1.53%±0.75 and 6.96%±0.76) and November in Tasmania and Victoria (7.34%±0.9 and 5.27%±0.81) potentially when feed availability and quality is highest. The incidence of dark cutting was highest for all states during the period from February to June. Lower pasture availability and quality in combination with higher levels of stress due to extreme high or low temperatures during this time could all contribute to the higher incidences. The findings of this study show that procurement and management decisions made by cattle buyers, producers and processors need to change throughout the year to help mitigate the incidence of dark cutting carcasses and reduce financial loss.

À l'occasion du 20ème anniversaire du «Meat Standards Australia (MSA)», le 64ème Congrès international sur la science et la technologie de la viande (ICoMST) a organisé une session spéciale le lundi 13 août 2018 à Melbourne pour décrire les activités de recherche à l'origine du développement du MSA. Le programme du workshop a permis de présenter le développement du MSA jusqu'à son rôle dansle marché d'aujourd'hui, et ce que l'avenir nous réserve pour ce système de classement des viandes le plus utilisé au monde. Les présentations de chercheurs et de professionnels du secteur sont résumées dans cet article.

The purpose of this study was to test if associations exist between plasma indicators of acute and chronic stress and lamb loin Warner Bratzler Shear Force (WBSF). Blood was collected at exsanguination from 2877 lambs from the Meat and Livestock Genetic Research flock with a suite of indicators analysed. Loin (M. longissimus lumborum) WBSF was measured after 5 days aging. Plasma indicators of stress did not relate to WBSF, however a positive association was found between WBSF and kill order, indicating that immediate pre-slaughter factors may be causing reduced tenderness in lamb. In addition, selection for decreased fat depth (PFAT) was associated with increased loin WSBF, indicating that genetic selection for increased carcass leanness is negatively affecting lamb loin tenderness.

The aim of this experiment was to evaluate the impact of selection for greater muscling on the adrenaline responsiveness of muscle, adipose and liver tissue, as reflected by changes in plasma levels of the intermediary metabolites lactate, non-esterified fatty acids (NEFA) and glucose. This study used 18-month-old steers from an Angus herd visually assessed and selected for divergence in muscling for over 15 years. Ten low muscled (Low), 11 high muscled (High) and 3 high muscled heterozygotes for myostatin mutation (HighHet) steers were challenged with adrenaline doses ranging between 0.2 to 3.0 μg/kg live weight. For each challenge, 16 blood samples were taken between -30 and 130 min relative to adrenaline administration. Plasma was analysed for NEFA, lactate and glucose concentration and area under curve (AUC) over time was calculated to reflect the tissue responses to adrenaline. Sixteen basal plasma samples from each animal were also assayed for growth hormone. Muscle glycogen and lactate concentration were analysed from four muscle biopsies taken from the 'semimembranosus', 'semitendinosus' and 'longissimus thoracis et lumborum' of each animal at 14, 90 and 150 days on an 'ad libitum' grain-based diet and at slaughter on day 157. In response to the adrenaline challenges, the High steers had 30% lower lactate AUC than the Low steers at challenges greater than 2 μg/kg live weight, indicating lower muscle responsiveness at the highest adrenaline doses. Aligning with this decrease in muscle response in the High animals were the muscle glycogen concentrations which were 6.1% higher in the High steers. These results suggest that selection for muscling could reduce the incidence of dark, firm, dry meat that is caused by low levels of glycogen at slaughter. At all levels of adrenaline challenge, the High steers had at least 30% greater NEFA AUC, indicating that their adipose tissue was more responsive to adrenaline, resulting in greater lipolysis. In agreement with this response, the High steers had a higher plasma growth hormone concentration, which is likely to have contributed to the increased lipolysis evident in these animals in response to adrenaline. This difference in lipolysis may in part explain the reduced fatness of muscular cattle. There was no effect of selection for muscling on liver responsiveness to adrenaline.

This study determined the impact of selection for greater muscling in Angus cattle on myofibre characteristics, muscle enzymatics, retail colour stability, pH decline and mineral content of the semimembranosus (SM), semitendinosus (ST) and longissimus thoracis (LT). Muscle from 10 low muscled (low) and 11 high muscled (high) steers were analysed. The high steers had myofibres 22% and 24% larger in cross-sectional area in the SM and ST (P < 0.05), and 8.6% less type IIX myofibres in the LT than the low steers (P < 0.05). The highs had 4.9% lower lactate dehydrogenase activity, 10.2% and 12.3% higher citrate synthase and isocitrate dehydrogenase activity than lows (P < 0.05). The highs had 27% more iron in the LT (P < 0.05). The results indicate that the oxidative capacity of muscle can be maintained in more muscular cattle with no detrimental effects to mineral content, pH decline or retail colour stability. Myofibre hypertrophy is one mechanism leading to greater muscle mass of these high muscled cattle.

The on-farm factors increasing the incidence of dark cutting were studied in 3145 pasture raised cattle consigned in 66 lots. Animal, environmental and farm management factors were recorded and pasture quantity, quality and mycotoxin concentrations were measured. The relative risk of dark cutting decreased by 26% in cattle grazing pastures with magnesium concentrations exceeding 0.24%. There was a 50% increase in relative dark cutting risk of cattle drinking from dams compared to drinking from troughs. Feeding supplements (hay/silage) in the last 7 days prior to slaughter reduced the relative risk of dark cutting by 25%. A high prevalence of mycotoxins was detected in pastures across all farms. In this case pasture ergot alkaloid concentrations above 600PPB increased the relative risk of dark cutting by 45%, while the presence of FumonisinB1 increased risk by 58%. In contrast the presence of 3acetyldeoxynivalenol reduced the relative dark cutting risk by 37%. Sex also affected the incidence of dark cutting, with heifers less likely to cut dark than steers by 47%.

The purpose of this study was to test if associations exist between plasma indicators of acute and chronic stress and lamb ultimate pH. Blood was collected at exsanguination from 2,877 lambs from the Meat and Livestock Australia Genetic Research flock with a suite of indicators analyzed. Ultimate pH was measured in the loin (M. longissimus lumborum) at 24 h post-slaughter. There was a positive association (P < 0.05) between ultimate pH and plasma glucose and lactate concentrations, which indicates that opportunities exist to reduce variation in ultimate pH by reducing stress in the preslaughter period. These effects were small by comparison to production factors, however further understanding of how to best manage lambs in the pre-slaughter period is required to minimize stress and maximize lamb wellbeing and meat quality.