Graham Gardner

Australian producers can enhance animal performance and profitability by selecting for lean meat yield and eating quality attributes using Australian Sheep Breeding Values (ASBVs). However, the impact of selecting for these traits on the consumer-perceived eating quality of a large range of lamb cuts has not been explored. From 824 lambs, eight cuts (knuckle, leg, loin, outside, rack, rump, shoulder, topside) were collected, along with the loin and topside from an additional 2288 animals (n = 3119 animals). Samples were assessed by untrained consumers (n = 18,720) for tenderness, juiciness, flavour liking and overall liking. Selection for increased lean meat yield had mainly a negative impact on the eating quality of several cuts within the Terminal sire type. Selection for improved eating quality through increased loin intramuscular fat content (IMF) improved the eating quality of the loin, rack, outside and leg cuts, primarily within the Terminal sire type. Improving eating quality through selection for reduced shear force at five days ageing (SF5) also improved consumer sensory perception of all cuts except the knuckle and outside. The improvement in eating quality through selection for increased IMF and reduced SF5 was not fully accounted for by the phenotypic traits of loin chemical IMF and Warner-Bratzler shear force, suggesting that these breeding values are impacting eating quality through additional mechanisms. Simultaneous selection for improved lean meat yield and eating quality demonstrated minimal effects on consumer sensory scores, implying the Australian sheepmeat industry can produce high-quality, lean products to consistently meet consumer expectations.
•Selection for increased intramuscular fat improved consumer eating quality.•Selection for reduced shear force improved consumer eating quality.•Greater impact of lean meat yield breeding values in Terminal sire type.•Minimal effect of selecting for lean meat yield and eating quality on sensory traits.

RNA‐binding proteins (RBPs) play a pivotal role in post‐transcriptional regulation of gene expression, critically influencing skeletal myogenesis, muscle growth, and regeneration. Despite the recent identification of RBP Rps27l (ribosomal protein S27‐like) as a regulator affecting myogenic proliferation and differentiation, its functions and regulatory mechanisms in skeletal muscle development remain largely unknown. In this study, it is observed that muscle‐specific Rps27l knock‐in (M─KI) mice exhibit significantly increased muscle mass, enlarged myofiber size, a higher proportion of fast‐twitch myofibers, and enhanced muscle regeneration capabilities compared to wild‐type controls. Overexpression of Rps27l promotes myoblast proliferation while inhibiting differentiation in skeletal muscle cells. Mechanistically, it is revealed that the expression of Rps27l is negatively regulated by SIX4, a myogenic transcription factor. The N‐terminal intrinsically disordered region of RPS27L facilitates liquid‐liquid phase separation (LLPS) and interacts with IGF1 to collaboratively regulate myogenesis. The findings uncover the novel regulatory roles of RPS27L in skeletal muscle and highlight the significance of RPS27L‐driven LLPS in myogenesis.

The impact of increasing lean meat yield (LMY) on consumer eating acceptance and its association with intramuscular fat (IMF) of lamb products was evaluated. Consumer sensory scores (overall liking, tenderness, juiciness, flavour liking) of the loin and topside were obtained from 3119 lambs, in addition to the knuckle, leg, outside, rack, rump and shoulder from a subset of these animals (n = 824). LMY indicators included GR tissue depth (measured 110 mm from dorsal midline of 12th rib), whole carcass and section (fore, saddle, hind) computed tomography (CT) lean% and cut weight of the loin and topside (as a percentage of the total carcass weight). Loin IMF was measured on all animals, with topside, outside, rump and shoulder IMF obtained from a subset of animals. Linear mixed models demonstrated a reduction in eating quality with increasing LMY in all cuts (P < 0.05) except the knuckle and leg. The impact on eating quality varied depending on the method used to estimate LMY, with the strongest association observed when using CT lean% measures, particularly section CT lean% from which the cut was taken. The effect of LMY on consumer eating quality was fully driven by IMF within the loin and rump cuts (P > 0.05) but only partially in the rack, outside and shoulder (P < 0.05). Results confirm the importance for simultaneous selection of LMY and IMF as key drivers of sheepmeat eating quality and the importance for the inclusion of on-line predictions of LMY in eating quality grading systems.

Untrained consumer-determined sensory scores of tenderness, juiciness, flavour liking, and overall liking possess a level of dependency due to poorer consumer ability to discriminate between these traits. Given that overall liking is strongly correlated to all traits, this study evaluated the contributions of sensory traits to the overall liking scores of Australian lamb. Tenderness, juiciness, flavour liking and overall liking of a range of lamb cuts were assessed by untrained Australian consumers (n = 18,720) following Meat Standards Australia protocols. The most important contributor to lamb overall liking was flavour liking (44.7%), followed by tenderness (28.3%) and juiciness (27.0%) (P < 0.05; R = 0.88). The contribution of the sensory traits to overall liking varied between meat quality categories, although the contribution of juiciness varied minimally. The contribution of flavour liking to overall liking became more important as loin intramuscular fat content increased. Whilst small differences in the contribution of tenderness and juiciness were present between cooking methods, untrained consumers evaluated overall liking in a similar manner regardless of cut type, demonstrating consumers' inherent ability to consistently evaluate meat products.

This study evaluated the impact of high oxygen modified atmosphere packaging (MAP) in four different combinations, 80 % oxygen and 20 % carbon dioxide (MAP80), 40 % oxygen, 20 % carbon dioxide and 40 % nitrogen (MAP40(20CO2)), 40 % oxygen, 60 % carbon dioxide (MAP40(60CO2)), and vacuum skin packaging (VSP) under different retail display times (3 or 8 days) on the sensory scores of lamb meat. Untrained consumer sensory scores for overall liking, tenderness, juiciness and liking of flavour were assessed on the M. longissimus lumborum (loin) and M. semimembranosus (topside) of 144 lambs. In general, MAP40(20CO2) samples received higher sensory scores than MAP80 (P < 0.05). While the high carbon dioxide MAP mixture MAP40(60CO2) scored similar to MAP80 (P > 0.05). Therefore, MAP40(20CO2) minimised the detrimental effects on eating quality and is a viable alternative to the widely used MAP80. However, the highest eating quality scores were still obtained with VSP (P < 0.05).

Dual Energy X-ray Absorptiometry (DXA) scanners operating at abattoir processing speeds are currently installed in six sheep meat abattoirs around Australia, predicting carcass composition as estimates of computed tomography (CT) determined fat %, lean %, and bone %. This study tested an updated bone-detection algorithm for these DXA scanners. This algorithm improved the precision of prediction for carcass fat% and lean%, but most notably for bone % (R2 = 0.92, RMSE = 0.61 %), compared to the previous algorithm (R2 = 0.51, RMSE = 1.57 %). This was due to improved allocation of bone-containing pixels, resulting from the inclusion of tissue thickness in the bone-detection equation. In a second experiment, the predictions from this new algorithm, along with an automated phantom calibration technique, were assessed relative to their ability to meet the AUS-MEAT accreditation accuracy standards required for predicting CT determined carcass fat%, lean%, and bone%. The DXA met these standards for predicting fat % (range 10.9 % - 37.1 %), lean % (range 49.0 % - 66.2 %), and bone % (range 11.6 % - 25.0 %), across three weight bands of light carcasses (<22 kg), mid-weight carcasses (22-28 kg), and heavy carcasses (>28 kg). This work allowed for the accreditation of DXA, enabling its predictions of carcass composition to be used for trading sheep carcasses in Australia. The accuracy of these predictions far exceed those provided by the historical industry measure of GR tissue depth, and hot carcass weight.

The current sheep Meat Standards Australia (MSA) model is a pathways system designed to improve the overall eating quality of Australian lamb, yet it is unable to predict individual consumer-based eating quality scores for specific cuts. This paper describes the methodology of using consumer sensory scores to create an objective composite eating quality prediction score linked to individual quality grades for different cuts. This methodology accounts for objective carcass measures that are being commercialised within the industry, such as intramuscular fat percentage and a measure of lean meat yield percentage. The model demonstrated that through utilising these carcass grading traits, an eating quality prediction can be made with an accuracy of 75 % and 72 % for the grill and roast cooking method respectively, however individual consumer variation remained substantial. The model will allow the supply chain to allocate cuts to different marketing strategies (branding) based on their eating quality performance whilst also reducing the chances of consumers being offered products that do not meet their expectations.

Breeding for meat quality increases the value of lambs and requires reliable genetic parameters to achieve balanced genetic progress. Meat tenderness, accomplished by selecting for lower shear force, is an important eating quality trait because of its relationship with consumer satisfaction. Factors influencing shear force, include the pH and temperature decline post-mortem which can contribute towards higher shear force values and increased variation across contemporary groups. This study explored if genetic parameters for shear force change when post slaughter covariates and heterogeneous variance are corrected for, using data from 32,223 animals from different sheep breeds. Results showed that removing extreme individuals and contemporary groups with high mean shear force values reduced residual variance, followed by a smaller reduction in additive genetic variance and little effect on heritability. Results show that edited data performed better at predicting progeny performance and reduced potential bias introduced in the genetic evaluation due to data quality. The effect of including post-slaughter covariates in the genetic analysis was tested by estimating different model predictability through regression of estimated breeding values against offspring performance, showing that the model including hot carcass weight performed better followed by the one including both carcass weight and C-site fat depth. Our results highlight that historic and current in-plant recording practices do not provide the capacity to account for non-genetic factors associated with abattoir environment that might be impacting the ability to accurately calculate shear force breeding values. In that sense, genetic evaluation can be improved by applying more rigorous data editing.

Intramuscular fat (IMF) % is an important measure of pork eating quality, with reduced IMF % linked to the selection of pigs with low backfat P2 thickness and more muscular genotypes over several decades. This experiment tested the association of IMF % from the M. longissimus thoracis et lumborum of 345 pigs at 3 abattoirs (sites) with computed tomography (CT) determined carcass composition (% lean or fat), accredited abattoir measures of P2 backfat (mm; Hennessy Grading Probe [HGP], AutoFom III, and PorkScan Lite) and the lean % output from abattoir devices (HGP, AutoFom III, and PorkScan Plus). There was a negative relationship between carcass CT lean % with IMF % at all sites (P < 0.05), with the strength of this relationship varying between sites. The strongest relationship was demonstrated at site 1 (R2 0.30, RMSE 0.59), and across a 4 SD range in the carcass lean % at each site, resulted in a decrease in loin IMF % of 1.56, 0.44, and 0.80. There was a positive relationship of carcass CT fat % with IMF %, with similar, albeit slightly stronger relationship to IMF than with CT lean %. In contrast, only one of the 3 sites with an accredited P2 measurement device demonstrated a significant association (P < 0.05) with IMF %. This is the first time the associations of IMF % with carcass CT composition has been assessed alongside that of P2 backfat measurements from commercially deployed abattoir devices. Given P2 backfat is the key industry measure on which carcass value is determined in Australia, this experiment demonstrates the limitations that P2 has in measuring and monitoring the associations of carcass lean and fat % with IMF. Ideally, an independent measure of IMF % would allow for independent selection for lean % and IMF %; however, there is currently no commercial device that can measure pork IMF %.

In 2016 an Australian project, the Advanced Livestock Measurement Technologies project (ALMTech), was initiated to accelerate the development and implementation of technologies that measure lean meat yield and eating quality. This led to the commercial testing, and implementation of a range of new technologies in the lamb, beef, and pork industries. For measuring lean meat yield %, these technologies included dual energy X-ray absorptiometry, hand-held microwave systems, and 3-D imaging systems. For measuring beef rib-eye traits and intramuscular fat %, both pre- and post-chilling technologies were developed. Post-chilling, a range of camera systems and near infrared spectrophotometers were developed. While pre-chilling, technologies included insertable needle probes, nuclear magnetic resonance, and X-ray systems. Initially these technologies were trained to predict the pre-existing traits already traded upon within industry. However, this approach was limiting because the technologies could measure attributes that were either non-existent in the trading language, were superior as calibrating standards, or more accurately reflected value than the pre-existing trait. Therefore, we introduced IMF% into the trading language for both beef and sheep meat, and carcase lean%, fat%, and bone% for sheep meat. These new technologies and the traits that they predict have delivered multiple benefits. Technology provider-companies are instilled with the confidence to commercialise due to the provision of achievable accreditation standards. Processors have the confidence to invest in these technologies and establish payment grids based upon their measurements. And lastly, it has enhanced data flow into genetic databases, industry data systems (MSA), and as feedback to producers.