Repeatability and reciprocity of the cone optoretinogram.

Optoretinography has enabled noninvasive visualization of physiological changes in cone photoreceptors exposed to light. Understanding the cone optoretinogram in healthy subjects is essential for establishing it as a biomarker for cone function in disease. Here, we measure the population cone intensity optoretinogram in healthy adults, for multiple irradiance/duration combinations of visible stimuli with equal energy. We study the within and between session repeatability and reciprocity of the ORG in five healthy subjects. We find the cone optoretinogram exhibits equivalent amplitudes for equal-energy stimuli. We also find good within-subject repeatability, which allows us to show differences across the five subjects.

The impact of weather on the incidence of dark cutting in Australian feedlot cattle.

This study conducted a retrospective analysis of historical Meat Standard Australia (MSA) carcass data in combination with Bureau of Meteorology (BOM) weather data, to evaluate the relationship between climatic conditions prior to feedlot departure on the incidence of dark cutting grain-fed beef. Data records for 2,795,754 carcasses from 17 commercial feedlots over a 6-year period were evaluated within this study. Carcasses were consigned to 16 abattoirs. Weather data from BOM were recorded at 30-min intervals and were obtained from weather stations with the closest proximity to each feedlot. These data were used to calculate the Temperature Humidity Index (THI). Climatic data were amalgamated into daily observations and a series of predictors including ambient temperature (TA, °C), relative humidity (RH, %), wind speed (WS, m/s), rainfall (mm) and THI. In addition, lag interactions from 24 h out to 28 days prior to exiting the feedlot were generated. The incidence of dark cutting was determined as percentage per cohort with an ultimate pH > 5.7. Data were analysed using three models: model 1 included feedlot, abattoir, hormone growth promotant status and sex as fixed effects. Model 2 incorporated the fixed effects within model 1 and minimum, maximum and standard deviation (SD) of TA and RH, daily range in TA, average WS and rainfall as random effects. Model 3 incorporated minimum, maximum, range and SD of THI, average WS and rainfall as random effects in addition to the fixed effects of model 1. The incidence of dark cutting within feedlot had a 10.1% range in estimated means with the lowest incidence was observed at feedlot 17 (0%) and highest incidence at feedlot 10 (10.1%). The inclusion of the climatic variables in model 2 and model 3 accounted for an additional 0.1 to 0.2% of the incidence of dark cutting carcasses. Higher maximum TA, RH and THI in the 3 to 28 days prior to consignment were all associated with an increased incidence of dark cutting (P < 0.05), but not in the 48 h preceding consignment (P > 0.05). Low minimum TA and low THI were also associated with an increase the incidence of dark cutting across all lag periods (P < 0.05). Increased variation in THI and TA in the 48 h prior to consignment increased dark cutting (P < 0.05) while increased standard deviation (SD) of temperature and THI range also increased dark cutting in the 14 and 28 day prior to feedlot exit (P < 0.05). Smaller minimum ranges in TA in the 28 days prior to consignment also reduced dark cutting (P < 0.05). Climatic conditions accounted for a further 0.1 to 0.2% of the incidence of dark cutting, whereas animal management factors, feedlot and abattoir were able to account for 21% of dark cutting. These data suggest that climatic conditions appear to have an inherent role in the incidence of dark cutting, albeit a small impact. Regardless, understanding the influence of climatic conditions on dark cutting allows for the implementation of management strategies within the supply chain to further reduce the impact of climatic conditions on grain-fed cattle.

Embedded microcomputer-based force plate system validation when evaluating lameness severity differentiation under an induced synovitis model in lactating dairy cattle.

Bovine lameness has relatively large negative economic and welfare implications on the U.S. dairy industry. Due to the ramifications, early lameness detection will aid in assisting dairy producers to mitigate downstream effects through early treatment. The objective of this study was to determine the minimum standing time required among 2-, 3-, 4-, 5-, and 10 min time intervals to obtain an accurate weight distribution estimate for each leg when attempting to detect lameness. An embedded microcomputer-based force plate system was developed to measure vertical forces from individual cow limb weight distribution to detect bovine lameness when utilizing an induced synovitis lameness model. The force plate has four quadrants, with each load cell quadrant measuring the force placed on it from a single limb. The force plate recorded weight (kg) every second from each load cell quadrant, after which, a 60 s moving average for weight distribution was calculated. A sequential study design was employed to evaluate non-lame and induced lameness to ensure time requirements were consistent. Prior to induction, the force plate system was used to measure weight distribution every second for 15 min. After lameness induction, additional 15 min increments were recorded every 24 h for seven days. Lameness was induced by injecting the left hind distal interphalangeal joint in three cows with amphotericin B, 12 h prior to the start of the study. Data were analyzed using a linear mixed effect that included the fixed effects of day relative to lameness induction, time period, foot and injected foot. Cow within replicate was included as a random effect. Cumulative minutes were assessed up to 15 min by comparing the least square rolling 60 s cumulative means expressed as a percentage of each animal's BW percentage placed on each leg for 2-, 3-, 4-, 5-, and 10 min intervals. Results indicate that the minimum time needed for accurate lameness detection in cows was 2 min.

Abattoir Factors Influencing the Incidence of Dark Cutting in Australian Grain-Fed Beef.

The aim of this study was to evaluate the effect of carcass traits, lairage time and weather conditions during lairage and abattoir factors that impact the incidence of dark cutting in 142,228 grain-fed carcasses, as defined by Meat Standards Australia (MSA) guidelines. This study was conducted over a 12-month period analysing data from cattle that were supplied from seven feedlots and processed at three abattoirs. Abattoir data indicated that the average incidence of dark cutting within the study was 2.8%. Increased wind speeds (WSs) and rain during lairage at the abattoir was associated with an increased risk of dark cutting, whereas variation in ambient temperature and/or relative humidity did not influence dark cutting. Heavier carcasses with whiter fat, larger hump heights, more rib fat, higher marble scores and lower ossification had lower incidences of dark cutting. The factors abattoir, time in lairage, time to grading and grader within Abattoir had significant effects on the incidence of dark cutting. The results from this study suggest that reducing the time in lairage and increasing the time between slaughter and grading are the two major ways to reduce dark cutting in MSA carcasses.

Refocusing cancer multidisciplinary team meetings in the United Kingdom: comparing urology with other specialties.

INTRODUCTION: Multidisciplinary team (MDT) meetings have been the gold standard of cancer care in the UK since the 1990s. We aimed to identify the views of urology cancer MDT members in the UK on improving the functioning of meetings and compare them with those of other specialties to manage the increasing demand on healthcare resources and enhance the care of complex cancer cases. METHODS: We analysed data from 2 national surveys distributed by Cancer Research UK focusing on the views of 2,294 and 1,258 MDT members about cancer MDT meetings. FINDINGS: Most breast, colorectal, lung and urology cancer MDT members felt meetings could be improved in the following areas: time for meeting preparation in job plans, streamlining of patients, auditing meeting decisions and prioritising complex cases. Most urology respondents (87%) agreed some patients could be managed outside a full MDT discussion, but this was lower for other specialties (lung 78%, breast 75%, colorectal 64%). CONCLUSIONS: To facilitate decisions on which patients require discussion in an MDT meeting, factors adding to case complexity across all tumour types were identified, including rare tumour type, cognitive impairment and previous treatment failure. This study confirms that urology MDT members are supportive of changing from reviewing all new cancer diagnoses to discussing complex cases but managing others with a more protocolised pathway. The mechanisms for how to do this and how to ensure the safety of patients require further clarification.

Randomized controlled trial comparison of analgesic drugs for control of pain associated with induced lameness in lactating dairy cattle.

Both the economic loss and welfare implications of lameness affect the dairy industry. Currently no analgesic drugs are approved to alleviate lameness-associated pain in lactating dairy cattle in the United States. In this randomized controlled trial, 48 lactating Holsteins were enrolled to evaluate the effect of oral meloxicam and i.v. flunixin meglumine on induced lameness. Cows were allocated to 1 of 4 treatment groups (n = 12 per group): lameness and flunixin meglumine (LAME + FLU); lameness and meloxicam (LAME + MEL); lameness and placebo (LAME + PLBO); or sham induction and placebo (SHAM + PLBO). Six hours before treatment, arthritis-synovitis was induced in the distal interphalangeal joint with 20 mg of amphotericin B, whereas SHAM cows were given an intra-articular injection of an equal volume (4 mL) of isotonic saline. Cows in LAME + FLU received 2.2 mg/kg flunixin meglumine i.v. and whey protein placebo orally; LAME + MEL were administered 1 mg/kg meloxicam orally and 2 mL/45 kg sterile saline placebo i.v.; LAME + PLBO were administered 2 mL/45 kg sterile saline placebo i.v. and whey protein placebo orally; and SHAM + PLBO received 2 mL/45 kg sterile saline placebo i.v. and whey protein placebo orally. The initial treatment of MEL, FLU, or PLBO was identified as time 0 h and followed by a second dose 24 h later with data collection for 120 h. The methods used to assess analgesic efficacy were electronic pressure mat, visual lameness assessment, visual analog score, plasma cortisol concentration, plasma substance P concentration, mechanical nociception threshold, and infrared thermography imaging. Linear mixed effect modeling was the primary method of statistical analysis. Visual lameness scoring indicated a lower proportion of the FLU + LAME group was lame at the T2 h and T8 h time points in comparison to the positive controls, whereas MEL therapy resulted in a lower proportion of lame cows at the T8 h time point. Cortisol area under the effect curve was lower following FLU therapy compared with LAME + PBLO for the 0-2 h (LSM difference = 35.1 ng·h/mL, 95% CI: 6.8, 63.3 ng·h/mL), 2-8 h (LSM difference = 120.6 ng·h/mL, 95% CI: 77.2, 164.0 ng·h/mL), and 0-24 h (LSM difference = 226.0 ng·h/mL, 95% CI: 103.3, 348.8 ng·h/mL) time intervals. Following MEL therapy, cortisol area under the effect curve was lower than LAME + PLBO for both the 2 to 8 h (LSM difference = 93.6 ng·h/mL, 95% CI: 50.2, 137.0 ng·h/mL) and 0 to 24 h time intervals (LSM difference = 187.6 ng·h/mL, 95% CI: 64.9, 310.4 ng·h/mL). Analysis of data from other assessment modalities failed to discern biologically relevant differences between treatment groups. We conclude that meaningful differences were evident for visual lameness assessment and cortisol from MEL and FLU treatment versus the positive control. Further clinical research is needed toward development of a model that will create reproducible events that are more pronounced in severity and duration of lameness which can be validated as a substitute for naturally occurring lameness cases.

Factors predictive of an advanced stage of colorectal cancer at presentation - a bi-national study.

AIM: Identifying elements associated with advanced colorectal cancer (CRC) stage may inform understanding of whether advanced disease is a corollary of access to healthcare or tumour biology and in turn allow the use of targeted screening and awareness programmes. The aim of this study was to identify factors that predict advanced stage of CRC at presentation in Australia and New Zealand. METHOD: This was a cross-sectional registry study sourced from the prospectively maintained Binational Colorectal Cancer Audit database of Australia and New Zealand. The primary outcome was stage as defined by the TNM system with associations drawn to demographic and perioperative variables. RESULTS: In total, 25 282 separate cancers were included. Univariate analysis found younger age, treatment at a public facility, increasing American Society of Anesthesiologists (ASA) grade, more distal tumours, and less recent year of surgery to all be associated with more advanced disease; sex and presentation at a rural vs urban hospital had no bearing on this outcome. Logistic regression identified younger age (< 60 years vs > 80 years: OR 1.96; 95% CI 1.80-2.14; P = 0.002), treatment at a public vs private hospital (OR 1.21; 95% CI 1.14-1.28; P < 0.001), increasing ASA grade (ASA4 vs ASA1: OR 1.37; 95% CI 1.17-1.59, P < 0.001) and more distal tumours (mid-low rectal vs right colon tumours: OR 1.52; 95% CI 1.41-1.64; P < 0.001) to be independent predictors of nodal or metastatic disease at presentation. CONCLUSION: Younger age, increasing ASA grade, more distal tumours, and treatment at a public rather than private facility are independently associated with the presence of nodal or distant CRC metastases at diagnosis.

Cerebrospinal fluid opening pressure: The effect of body mass index and body composition.

OBJECTIVES: Idiopathic intracranial hypertension (IIH) is strongly related to obesity. The relationship between intracranial pressure, body mass index (BMI), percentage body fat and distribution of body fat in non-IIH patients remains less clear. The aim of this study was to examine the relationship between intracranial pressure and body type in non-IIH patients. PATIENTS AND METHODS: Lumbar puncture manometry was used to measure cerebrospinal fluid opening pressure (CSFOP). BMI, in addition to neck, waist and hip circumferences were calculated. Air displacement plethysmography (BODPOD) was used to assess body composition. RESULTS: Data was collected from 100 subjects. 11 subjects with conditions known to cause raised intracranial pressure were excluded from analysis. According to Pearson correlation factors displaying a significant relationship with CSFOP included: BMI (R = 0.635, p < 0.0001); waist circumference (R = 0.498, p < 0.0001), hip circumference (R = 0.513, p < 0.0001) and percentage body fat (R = 0.435, p < 0.001). Multivariate analysis indicated that BMI was the only independent factor which predicted CSFOP. Sub-analysis according to gender indicated that BMI was predictive in females and percentage body fat was predictive in males. We did not identify any differences in BMI, percentage body fat or distribution of body fat in 7 IIH patients and 7 wt-matched non-IIH patients. CONCLUSION: BMI and percentage body fat both positively correlated with CSFOP, but BMI was more predictive in women and percentage body fat was more predictive in men. We did not find a relationship between distribution of body fat and CSFOP.

Short communication: Determination of the milk pharmacokinetics and depletion of milk residues of flunixin following transdermal administration to lactating Holstein cows.

Flunixin is a nonsteroidal anti-inflammatory drug and the most commonly prescribed analgesic in cattle in the United States. Recently, the US Food and Drug Administration (FDA) approved a transdermal formulation of flunixin for control of pyrexia associated with bovine respiratory disease and the control of pain associated with foot rot. The transdermal formulation is not currently approved for use in lactating dairy cattle in the United States, but extra-label use in dairy cattle is permissible under US regulations. The objectives of this study were to determine the pharmacokinetics in milk of dairy cows treated with transdermal flunixin and determine an appropriate withdrawal time for milk. Ten lactating Holstein cows were enrolled into the study in mid lactation. Following treatment, cows were milked 3 times per day through 144 h. Milk samples were collected for drug analysis using ultra-high-pressure liquid chromatography coupled with a triple quadrupole mass spectrometer. The geometric mean maximum concentration for flunixin in milk was 0.010 µg/mL and was 0.061 µg/mL for the active metabolite, 5-hydroxyflunixin. The geometric mean terminal half-life was 20.71 h for flunixin and 22.62 h for 5-hydroxyflunixin. Calculations to approximate a withdrawal time in milk following transdermal flunixin administration were accomplished using a statistical tolerance limit procedure. This analysis indicated that it would be prudent to observe a withdrawal period of 96 h following the last treatment. This is more than twice as long as the labeled withdrawal period of 36 h following use of the injectable formulation. The withdrawal period suggested by this work should be applied carefully, as this study was not conducted under the full quality control practices required by the US FDA for a full drug approval study. Caution should be taken when applying this withdrawal time to diseased animals, animals that are milked with different milking frequencies, and those in different stages of production as these have all been shown to affect drug depletion from milk.

Review: Analysis of the process and drivers for cellular meat production.

Cell-based meat, also called 'clean', lab, synthetic or in vitro meat, has attracted much media interest recently. Consumer demand for cellular meat production derives principally from concerns over environment and animal welfare, while secondary considerations include consumer and public health aspects of animal production, and food security. The present limitations to cellular meat production include the identification of immortal cell lines, availability of cost-effective, bovine-serum-free growth medium for cell proliferation and maturation, scaffold materials for cell growth, scaling up to an industrial level, regulatory and labelling issues and at what stage mixing of myo-, adipo- and even fibrocytes can potentially occur. Consumer perceptions that cell-based meat production will result in improvements to animal welfare and the environment have been challenged, with the outcome needing to wait until the processes used in cell-based meat are close to a commercial reality. Challenges for cell-based meat products include the simulation of nutritional attributes, texture, flavour and mouthfeel of animal-derived meat products. There is some question over whether consumers will accept the technology, but likely there will be acceptance of cell-based meat products, in particular market segments. Currently, the cost of growth media, industry scale-up of specific components of the cell culture process, intellectual property sharing issues and regulatory hurdles mean that it will likely require an extended period for cellular meat to be consistently available in high-end restaurants and even longer to be available for the mass market. The progress in plant-based meat analogues is already well achieved, with products such as the ImpossibleTM Burger and other products already available. These developments may make the development of cellular meat products obsolete. But the challenges remain of mimicking not only the nutritional attributes, flavour, shape and structure of real meat, but also the changes in regulation and labelling.

Changes in local free-living parasite populations in response to cleaner manipulation over 12 years.

Predation on parasites is an important ecological process, but few experimental studies have examined the long-term impacts on the prey. Cleaner fish prey upon large numbers and selectively feed on the larger individuals of the ectoparasitic stage of gnathiid isopods. Removal of cleaner fish Labroides dimidiatus for 1.5-12.5 years negatively affects coral reef fishes, but the mechanism is unclear. A reduction in local parasite populations or the size of individual parasites would benefit all susceptible fishes. We tested whether cleaner presence reduces local gnathiid populations using 18 patch-reefs distributed between two sites (both at Lizard Island, Great Barrier Reef) which were maintained cleaner-free or undisturbed for 12 years. Using emergence traps (1 m2), free-living gnathiid stages were sampled before and after cleaner fish were removed during the day and night, up to 11 times over the course of the experiment. There were effects of the removal in the predicted direction, driven largely by the response at one site over the other involving 200% more gnathiids, but manifested only in the daytime sampling after 4 months. There was also a main effect (36%) for the shared sample dates at both sites after 12 years. Gnathiid size occasionally differed with cleaner presence, but in no consistent way over time. Contrary to our predictions, changes in free-living gnathiid population numbers and their size structure rarely reflected the changes in fish populations and individuals observed on cleaner-free reefs. Therefore, evidence that this predator alone regulates gnathiids remains limited, suggesting other contributing processes are involved.

Genetic variation in colour stability traits of lamb cuts under two packaging systems.

Data from samples of longissmus lumborum (LL) and semimembranosus (SM) muscles from 391 lamb carcasses, which had been packaged in overwrap (OW) or high oxygen modified atmosphere packaging (MAPO2) systems and then subjected to simulated retail display, were used to estimate genetic variation for colour stability traits of lamb meat as a step in identifying a trait for genetic evaluation. Traits included the ratio of the reflectance of light at wavelengths of 630 nm and 580 nm (oxy/met) measured at a single time point at the end of the display period (day 3 under OW; day 8 under MAPO2) and the predicted time for oxy/met to reach a benchmark value. Under OW and MAPO2, the measures of meat colour stability of the LL tended to be of moderate heritability (0.09-0.29), but for the SM were of low heritability (0-0.10). Improving retail colour stability of lamb loins through selection of genetically superior animals may be better based on measurement of oxy/met.

Differences in light scattering between pale and dark beef longissimus thoracis muscles are primarily caused by differences in the myofilament lattice, myofibril and muscle fibre transverse spacings.

Beef colour is essential to consumer acceptability with dark muscle colours being problematic. Dark meat has less light scattering but the mechanisms are unknown. We hypothesise that three mechanisms are responsible for decreased light scattering in dark meat, namely (i) larger lateral separation of myofilaments, (ii) decreased optical protein density in the I-band and (iii) decreased denaturation of sarcoplasmic proteins. Nineteen beef longissimus thoracis muscles, divided into 'light', 'medium' and 'dark' colour groups, were assessed for light scattering by reflectance confocal microscopy, sarcomere length, and myofilament lattice spacing by small-angle X-ray diffraction. Dark muscles had a longer lattice spacing, shorter sarcomeres and wider muscle fibre diameters compared to lighter colour groups, indicating that the transverse spacing of muscle fibres that occurs post-mortem, with pH decline, is central to light scattering development. Dark muscles also had more degradation of the Z-disc and higher sarcoplasmic protein activities, which could impact on the optical density and contribute to lower light scattering.

Derivatives of a benzoquinone acyl hydrazone with activity against Toxoplasma gondii.

Toxoplasma gondii is an obligate intracellular parasite with global incidence. The acute infection, toxoplasmosis, is treatable but current regimens have poor host tolerance and no cure has been found for latent infections. This work builds upon a previous high throughput screen which identified benzoquinone acyl hydrazone (KG8) as the most promising compound; KG8 displayed potent in vitro activity against T. gondii but only marginal in vivo efficacy in a T. gondii animal model. To define the potential of this new lead compound, we now describe a baseline structure-activity relationship for this chemotype. Several derivatives displayed IC50's comparable to that of the control treatment pyrimethamine with little to no cytotoxicity. The best of these, KGW44 and KGW59, had higher metabolic stability than KG8. In an in vivo T. gondii murine model, KGW59 significantly increased survivorship. This work provides new insights for optimization of this novel chemotype.

A high rigor temperature, not sarcomere length, determines light scattering properties and muscle colour in beef M. sternomandibularis meat and muscle fibres.

Beef meat colour is impacted by both myoglobin status and the light scattering properties of the muscle, and the specific causative scattering elements of the latter are still unknown. We hypothesize that stretching muscles during rigor will generate a structure which favours light scattering, by increasing the length of the I-band (longer sarcomeres) and that a high rigor temperature will cause protein reconfiguration, changing the muscle structure and promoting light scattering. Muscle fibre fragments were isolated from four beef M. sternomandibularis and subjected to stretching (plus, minus) and three incubation temperatures (5, 15, 35 °C). Reflectance confocal laser scanning microscopy (rCLSM) revealed sarcomere stretching alone was not solely responsible for light scattering development. A high rigor temperature (35 °C) was more favourable for light scattering. Stretching and taking muscle into rigor at 35 °C promoted transverse shrinkage of muscle fibres and increased light scattering and could be applied post-mortem (PM) to reduce the occurrence of problematic dark meat.

Impact of specialist management on survival from radiation-associated angiosarcoma of the breast.

BACKGROUND: Radiation-associated angiosarcoma of the breast (RAAS) is a rare complication of adjuvant radiotherapy associated with poor survival. The British Sarcoma Group guidelines recommend that all angiosarcomas are referred to a sarcoma multidisciplinary team, although there is no recommendation that patients are managed within a sarcoma service. The aims of this study were to compare survival, complete excision rates and local recurrence rates of patients managed within a sarcoma service and those managed within local hospitals. METHODS: All patients with RAAS referred to a regional sarcoma service between 1998 and 2015 were identified from prospective databases. Patient records, and radiology, pathology and operation notes were reviewed retrospectively. RESULTS: Thirty-six patients were operated on with curative intent; 26 were managed by the sarcoma service (of whom 21 underwent radical excision of the irradiated field followed by chest wall reconstruction) and ten were managed locally. Median age was 69·5 (range 43-85) years. Disease-specific survival was significantly longer in patients managed by the sarcoma service than in those managed locally: median 91·1 (range 69·2-113·0) versus 48·8 (18·6-79·1) months respectively (P = 0·012). Overall survival rates were similar (P = 0·112). There was no difference in complete excision rate (18 of 26 in sarcoma service versus 5 of 10 in local services; P = 0·456), although the local recurrence rate was significantly lower among patients managed by the sarcoma service (9 of 26 versus 8 of 10; P = 0·015). CONCLUSION: Specialist management of RAAS leads to fewer local recurrences and improved disease-specific survival. Early referral and management within specialist units is recommended.

Genetic correlations between wool traits and meat quality traits in Merino sheep.

Genetic correlations between 29 wool production and quality traits and 25 meat quality and nutritional value traits were estimated for Merino sheep from an Information Nucleus (IN). Genetic correlations among the meat quality and nutritional value traits are also reported. The IN comprised 8 flocks linked genetically and managed across a range of sheep production environments in Australia. The wool traits included over 5,000 yearling and 3,700 adult records for fleece weight, fiber diameter, staple length, staple strength, fiber diameter variation, scoured wool color, and visual scores for breech and body wrinkle. The meat quality traits were measured on samples from the and included over 1,200 records from progeny of over 170 sires for intramuscular fat (IMF), shear force of meat aged for 5 d (SF5), 24 h postmortem pH (pHLL; also measured in the , pHST), fresh and retail meat color and meat nutritional value traits such as iron and zinc levels, and long-chain omega-3 and omega-6 polyunsaturated fatty acid levels. Estimated heritabilities for IMF, SF5, pHLL, pHST, retail meat color lightness (), myoglobin, iron, zinc and across the range of long-chain fatty acids were 0.58 ± 0.11, 0.10 ± 0.09, 0.15 ± 0.07, 0.20 ± 0.10, 0.59 ± 0.15, 0.31 ± 0.09, 0.20 ± 0.09, 0.11 ± 0.09, and range of 0.00 (eicosapentaenoic, docosapentaenoic, and arachidonic acids) to 0.14 ± 0.07 (linoleic acid), respectively. The genetic correlations between the wool production and meat quality traits were low to negligible and indicate that wool breeding programs will have little or no effect on meat quality. There were moderately favorable genetic correlations between important yearling wool production traits and the omega-3 fatty acids that were reduced for corresponding adult wool production traits, but these correlations are unlikely to be important in wool/meat breeding programs because they have high SE, and the omega-3 traits have little or no genetic variance. Significant genetic correlations among the meat quality traits included IMF with SF5 (-0.76 ± 0.24), fresh meat color * (0.50 ± 0.18), and zinc (0.41 ± 0.19). Selection to increase IMF will improve meat tenderness and color which may address some of the issues with Merino meat quality. These estimated parameters allow Merino breeders to combine wool and meat objectives without compromising meat quality.

High pH in beef longissimus thoracis reduces muscle fibre transverse shrinkage and light scattering which contributes to the dark colour.

Most studies have focused on myoglobin regarding meat colour development, with little focus on the contribution of muscle structure and light scattering. Our aim was to investigate the pH-dependent changes in muscle structure, on the light scattering properties of the meat. Beef longissimus thoracis muscles were segregated into light, medium or dark colour groups (n=18). 'Dark' muscles had a high ultimate pH (pHu), lower lightness (L*), redness (a*), higher myoglobin concentration and deoxymyoglobin content compared to other muscles. Reflectance confocal laser scanning microscopy (rCLSM) revealed 'dark' muscles had decreased global brightness (indicator of light scattering) and increased fibre width. In a secondary experiment, decreasing the homogenisation buffer pH from 6.10 to 5.40 induced a 17% shrinkage in high pHu muscle fibres, which increased light scattering by ~25%. In conclusion, rCLSM demonstrated that muscle structure contributes to the magnitude of light scattering by a pH dependent mechanism.