Gregory S. Harper

A major aim of the research program known as SheepGENOMICS was to deliver DNA markers for commercial breeding programs. To that end, a resource flock was established, comprehensively phenotyped and genotyped with DNA markers. The flock of nearly 5000 sheep, born over two consecutive years, was extensively phenotyped, with more than 100 recorded observations being made on most of the animals. This generated more than 460 000 records over 17 months of gathering information on each animal. Here, we describe the experimental design and sample-collection procedures, and provide a summary of the basic measurements taken. Data from this project are being used to identify collections of genome markers for estimating genomic breeding values for new sheep industry traits.

Stand-alone environmental indicators based on life cycle assessment (LCA), such as the carbon footprint and water footprint, are becoming increasingly popular as a means of directing sustainable production and consumption. However, individually, these metrics violate the principle of LCA known as comprehensiveness and do not necessarily provide an indication of overall environmental impact. In this study, the carbon footprints for six diverse beef cattle production systems in southern Australia were calculated and found to range from 10.1 to 12.7 kg CO₂e kg⁻¹ live weight (cradle to farm gate). This compared to water footprints, which ranged from 3.3 to 221 L H₂Oe kg⁻¹ live weight. For these systems, the life cycle impacts of greenhouse gas (GHG) emissions and water use were subsequently modelled using endpoint indicators and aggregated to enable comparison. In all cases, impacts from GHG emissions were most important, representing 93 to 99% of the combined scores. As such, the industry’s existing priority of GHG emissions reduction is affirmed. In an attempt to balance the demands of comprehensiveness and simplicity, to achieve reliable public reporting of the environmental impacts of a large number of products across the economy, a multi-indicator approach based on combined midpoint and endpoint life cycle impact assessment modelling is proposed. For agri-food products, impacts from land use should also be included as tradeoffs between GHG emissions, water use and land use are common.

Based on an association with extracellular matrix remodelling, mitosis, proliferation and adipogenic differentiation, the glycosaminoglycan hyaluronan (HA) was assessed as a marker for intramuscular fat (IMF) development (marbling) in bovine loin muscle (longissimus dorsi, LD). Loin samples collected from the quartering site of feedlot-finished Wagyu–Angus and Jersey–Limousin steers were assayed for percentage IMF (IMF%) and HA after assignment of AUS-MEAT marbling scores. There was a moderate phenotypic correlation (r2 = 0.69) between IMF% and marbling score but little variance was explained by HA concentration. Breed was not a significant factor in marbling score or IMF% but did influence the HA concentration of the LD, with Wagyu–Angus steers having 2-fold more HA than Jersey–Limousin steers at the same marbling score. The non-linear decline in fat-adjusted HA levels as marbling score increased suggests that HA concentration was associated with lean growth potential of the muscle rather than adipogenesis. Using a different experimental approach, differences in distribution and amount of HA could not be discerned in histological sections of LD from age-matched Wagyu–Hereford heifers allocated to a low (score 1) or medium (score 3) marbling score group. These findings were consistent with the absence of differences between the two groups for other indicators of fatness (IMF% and P8 fat depth), maturity and myofibre characteristics despite an increase in oxidative capacity of the muscle with age. The data support the conclusion that the concentration of HA in the LD alone was not predictive of development of intramuscular fat.

SUMMARY: We investigated the effect of prolonged immobilisation of six and nine months duration on the morphology and antioxidant biochemistry of skeletal muscles in the amphibian aestivator Cyclorana alboguttata. We hypothesised that, in the event of atrophy occurring during aestivation,larger jumping muscles were more likely to be preserved over smaller non-jumping muscles. Whole muscle mass (g), muscle cross-sectional area (CSA)(μm2), water content (%) and myofibre number (per mm2) remained unchanged in the cruralis muscle after six to nine months of aestivation; however, myofibre area (μm2) was significantly reduced. Whole muscle mass, water content, myofibre number and myofibre CSA remained unchanged in the gastrocnemius muscle after six to nine months of aestivation. However, iliofibularis dry muscle mass, whole muscle CSA and myofibre CSA was significantly reduced during aestivation. Similarly,sartorius dry muscle mass, water content and whole muscle CSA was significantly reduced during aestivation. Endogenous antioxidants were maintained at control levels throughout aestivation in all four muscles. The results suggest changes to muscle morphology during aestivation may occur when lipid reserves have been depleted and protein becomes the primary fuel substrate for preserving basal metabolic processes. Muscle atrophy as a result of this protein catabolism may be correlated with locomotor function, with smaller non-jumping muscles preferentially used as a protein source during fasting over larger jumping muscles. Higher levels of endogenous antioxidants in the jumping muscles may confer a protective advantage against oxidative damage during aestivation; however, it is not clear whether they play a role during aestivation or upon resumption of normal metabolic activity.

This study determined the extent to which bovine longissimus lumborum muscle (LLM) myofibers are influenced by nutrition for 120 d from weaning and the time-course of recovery after severe postweaning nutritional restriction. After weaning, 3 groups of Belmont Red cattle, a tropically adapted breed, were fed to achieve rapid growth (RG, ≥0.6 kg of BW gain/d; n = 16), slow growth (SG, 0.2 kg of BW gain/d; n = 17), or BW loss (WL, 10% loss of weaning weight; n = 17) over 120 d. They were then grazed as 1 group at pasture with forage supplementation for 600 d until slaughter at approximately 500 kg of BW. Samples of LLM were taken from 8 to 12 animals per treatment 6 d before (baseline) and 115, 204, 324, and 476 d after commencement of the study and from all cattle at slaughter (d 721). Myofiber characteristics were determined by immunocytochemical staining of myosin heavy chains. Cross-sectional areas (CSA) of the major myofiber types 1, 2A, and 2X in WL were reduced at d 115 compared with baseline and with the growth groups (all P < 0.001); however, there was little difference in the percentage of the different myofiber types (all P > 0.10). Differences in CSA of the major myofiber types between WL and the growth groups at 115 d were smallest for type 1 (slow oxidative) and greatest for type 2X (fast glycolytic). Consequently, the relative area (percentage of total myofiber area) of type 1 myofibers in WL was significantly greater at 115 d than in the growth groups (P < 0.001). During recovery from postweaning nutritional restriction, significant differences in major myofiber type percentages were not evident (all P > 0.10), and by 721 d CSA of myofiber types differed little between the treatment groups, although SG had greater CSA of type 1 (P < 0.05) and type 2A (P < 0.01) myofibers than WL and RG. At 721 d, the relative area of type 2A myofibers was less in WL compared with SG (P < 0.01) and RG (P < 0.05) and of type 2X myofibers greater (P < 0.05) in WL compared with SG. It is concluded that in the LLM of cattle undergoing severe nutritional restriction immediately postweaning, the size of the more glycolytic fiber types is more adversely affected than the more oxidative types, resulting in an increased relative area of type 1, slow oxidative myofibers. However, given adequate time and nutriment at pasture, LLM myofiber characteristics of cattle recovered to near normal after severe, chronic nutritional restriction immediately postweaning, consistent with earlier findings for beef quality. Copyright © 2009. .

Green-striped burrowing frogs, Cyclorana alboguttata, survive droughts by entering a metabolic depression called aestivation, characterised by a reduction in resting oxygen consumption by 80%. Aestivation in C. alboguttata is manifest by transcriptional silencing of skeletal muscle bioenergetic genes, such as NADH ubiquinone oxidoreductase 1, ATP synthase and superoxide dismutase 2. In this study, we hypothesised that aestivation is associated with epigenetic change in frog muscle. We assessed mRNA transcript abundance of seven genes that code for proteins with established roles in epigenetically-mediated gene silencing [transcriptional co-repressor SIN3A, DNA (cytosine-5-) methyltransferase 1, methyl CpG binding protein 2, chromodomain helicase DNA binding protein 4, histone binding protein rbbp4, histone deacetylase 1 and nuclear receptor co-repressor 2] using qRT-PCR. These seven genes showed a modest (1.1–3.5-fold) but coordinated upregulation in 6-month aestivating muscle. This reached significance for SIN3A and DNA cytosine-5-methyltransferase 1 in standard pair-wise comparisons (p < 0.05), and the candidates as a whole when analysed by Fisher’s combined probability test (p < 0.01). These data are consistent with the hypothesis that the transcriptional silencing and metabolic depression that occurs during seasonal dormancy are associated with chromatin remodelling, and present a novel example of an environmentally induced epigenetic modification in an adult vertebrate.