Association between Loin Ultimate pH and Plasma Indicators of Pre-Slaughter Stressors in Australian Lamb

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 (

Association between Loin Ultimate pH and Plasma Indicators of Pre-Slaughter Stressors in Australian Lamb

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 pre-slaughter 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

Initial Bloom Color is a Poor Predictor of Retail Color Stability in Lamb Loin Meat

The rapid browning of lamb meat on retail display reduces its appeal to consumers and thus the marketability of lamb meat. Predicting the rate of meat browning on retail display would allow retailers to effectively manage this issue. The ability of bloomed meat color at the start of retail display to predict meat browning over subsequent retail display was investigated in lamb loin meat. Mixed breed lambs (n = 4404) produced at 5 sites over 5 yr were slaughtered at ∼23kg carcass weight and measured for loin pH at 24 h, myoglobin, iron and zinc concentrations, isocitrate dehydrogenase activity and intramuscular fat. Loin meat was aged for 5 d before being re-sliced and overwrapped for color measurement over a 72 h simulated retail display. Meat redness (R630/R580) was measured after blooming and every 24 h across display using a Hunterlab spectrophotometer. Simple and partial correlation coefficients between initial and subsequent R630/R580 measures over the display were low (≤ 0.4). Accounting for key muscle traits influencing meat color such as pH24, myoglobin, iron or intramuscular fat concentration did not improve these correlations between bloomed meat color and subsequent meat color over retail display. Therefore bloomed meat color at the start of display is not a useful predictor of meat browning after 24 h of retail display. Alternatively, correlations between 24, 48, and 72 h R630/R580 were > 0.8, suggesting that meat color measured from 24 h of display can accurately predict subsequent retail meat browning

Towards classical geometrodynamics from Group Field Theory hydrodynamics

We take the first steps towards identifying the hydrodynamics of group field theories (GFTs) and relating this hydrodynamic regime to classical geometrodynamics of continuum space. We apply to GFT mean field theory techniques borrowed from the theory of Bose condensates, alongside standard GFT and spin foam techniques. The mean field configuration we study is, in turn, obtained from loop quantum gravity coherent states. We work in the context of 2d and 3d GFT models, in euclidean signature, both ordinary and colored, as examples of a procedure that has a more general validity. We also extract the effective dynamics of the system around the mean field configurations, and discuss the role of GFT symmetries in going from microscopic to effective dynamics. In the process, we obtain additional insights on the GFT formalism itself.Comment: revtex4, 32 pages. Contribution submitted to the focus issue of the New Journal of Physics on "Classical and Quantum Analogues for Gravitational Phenomena and Related Effects", R. Schuetzhold, U. Leonhardt and C. Maia, Eds; v2: typos corrected, references updated, to match the published versio

Spontaneous vortices in the formation of Bose-Einstein condensates

Phase transitions are ubiquitous in nature, ranging from protein folding and denaturisation, to the superconductor-insulator quantum phase transition, to the decoupling of forces in the early universe. Remarkably, phase transitions can be arranged into universality classes, where systems having unrelated microscopic physics exhibit identical scaling behaviour near the critical point. Here we present an experimental and theoretical study of the Bose-Einstein condensation phase transition of an atomic gas, focusing on one prominent universal element of phase transition dynamics: the spontaneous formation of topological defects during a quench through the transition. While the microscopic dynamics of defect formation in phase transitions are generally difficult to investigate, particularly for superfluid phase transitions, Bose-Einstein condensates (BECs) offer unique experimental and theoretical opportunities for probing such details. Although spontaneously formed vortices in the condensation transition have been previously predicted to occur, our results encompass the first experimental observations and statistical characterisation of spontaneous vortex formation in the condensation transition. Using microscopic theories that incorporate atomic interactions and quantum and thermal fluctuations of a finite-temperature Bose gas, we simulate condensation and observe vortex formation in close quantitative agreement with our experimental results. Our studies provide further understanding of the development of coherence in superfluids, and may allow for direct investigation of universal phase-transition dynamics.Comment: 14 pages, 6 figures. Accepted for publication in Nature. Supplementary movie files are available at http://www.physics.uq.edu.au/people/mdavis/spontaneous_vortice

Breeding to Improve Meat Eating Quality in Terminal Sire Sheep Breeds

An economic value for sheep meat eating quality was derived using consumer taste panel sensory trait scores and willingness to pay data. Improving eating quality by one score generated a price premium to commercial producers of $0.15/kg relative to a carcass price of$4.50/kg. Eating quality was included in a breeding objective with growth and lean meat yield. Under selection index scenarios modelled, simultaneous improvement of all traits was only possible with genomic testing of male selection candidates due to antagonistic correlations involving yield, eating quality, intramuscular fat, and shear force. Economic gain could be increased by up to 20% compared to current industry selection indexes

Genetic and nutritional regulation of lamb growth and muscle characteristics

Combined actions of nutrition and genetic regulation of the growth rate of lambs as well as the physical, biochemical, and eating quality characteristics of their skeletal muscle were assessed in a major field experiment. Data arising were collated and integrated to consolidate findings made at the farm, animal, tissue, cellular, and gene expression levels. At the farm level, increased nutrient availability significantly increased the growth rate of crossbred lambs and increased the growth advantage resulting from the use of sires with high estimated breeding values (EBV) for growth. In contrast, the extra depth of the 'M. longissimus thoracis et lumborum' (EMD) arising from sires with a higher EBV for this trait was constant irrespective of nutrition. Ewe liveweight and body condition were critical in determining the pre-weaning nutrition and growth of lambs, with the LOW plane of nutrition causing stunting of forelimb bones and changes to the allometric growth coefficients for carcass lean and fat. The EBV of the sire for muscling (PEMD) influenced several non-muscling traits, and interactions with nutrition suggested that on HIGH nutrition, absorbed nutrients were partitioned away from wool and fat accretion and towards protein accretion in lambs having superior muscling genetics. Expression levels of known myogenic factors in muscle, together with a suite of peptides and proteins whose identity and levels were determined by proteomic screening, contributed to improved understanding of the mechanisms underpinning nutritional and genetic regulation of skeletal muscle development. The study revealed the need for caution in the use of indirect markers of growth or composition, with their usefulness being constrained if the localisation of the response to selection is specific to parts of the carcass where the selection had initially been concentrated. As well, the possibility that much of the variation explained by potential physiological markers can be accounted for by non-invasive measures of growth and fatness currently used by Australian farmers must be considered

Relationship between animal age, intramuscular fat, cooking loss, pH, shear force and eating quality of aged meat from sheep

The relationships between sensory traits (tenderness, juiciness, flavour and overall liking) and objective measures, such as shear force, intramuscular fat, cooking loss, pH and animal age, were derived for 'M. longissimus thoracis et lumborum' (LL) from 471 lamb and sheep carcasses. Tenderness could be predicted with the most accuracy (R² = 0.24) and flavour with the highest precision (r.s.d. = 7.5 units) when using the objective measures, which may be in part due to the small variation in the range of shear force values of the samples (all carcasses electrically stimulated and meat aged for 5 days) and the use of consumer panels for the assessment of sensory traits. The ultimate pH of the LL, the rate of decline in pH in the LL or the predicted temperature at pH 6.0 were not significant predictors of the sensory traits when tested on a subsample of the carcasses. The model coefficients indicated that all sensory traits (tenderness, flavour, juiciness and overall liking) declined as shear force and age increased, and as intramuscular fat percentage decreased. This translated into a decline of 16 points on average for tenderness and 13 points for overall liking when LL samples from 68.5-month-old sheep were compared with those from unweaned lambs, when adjusted to the same level of intramuscular fat and shear force. Predictions of the sensory traits at varying levels of shear force were made and show that at 49 Newtons (N), the overall liking score would be 51 and the tenderness score 48. Derived relationships between objective meat quality measures and sensory traits suggest that to achieve a failure rate of no more than 10% for loin meat when eaten, it must have a shear force of about 27 N or less