DAIRY DEREGULATION AND LOW-INPUT DAIRY PRODUCTION: A BIOECONOMIC EVALUATION

Deregulation of the Australian dairy industry could affect the utilization of resources by milk producers and the profitability of dairy production. In this study we examine the feed mix that dairy producers use, both pastures and supplements, under partial and total deregulation. We are particularly interested in the interaction of pasture utilization and farm profitability. The results of this research demonstrate that profitable low-input dairy is constrained by the most limiting resource, feed supplied by pasture, and that the interactions between economic and biological processes are critical to farm profitability.Agricultural and Food Policy, Production Economics,

DYNAMICS OF OPTIMAL INTERACTIONS BETWEEN PASTURE PRODUCTION AND MILK YIELDS OF AUSTRALIAN DAIRY FARMS

Deregulation of the Australian dairy industry could effect the utilization of resources by milk producers. In this study we examine the feed input mix dairy producers use, both pastures and supplements, prior to and after deregulation. We are particularly interested in the interaction of pasture utilization and farm profitability.dairy production, pasture utilization, deregulation, Land Economics/Use, Livestock Production/Industries,

Excess noise characteristics of Al0.8Ga0.2As avalanche photodiodes

The avalanche noise characteristics of Al0.8Ga0.2 As have been measured in a range of p-i-n and n-i-p diodes with i-region widths ω varying from 1.02 to 0.02 μm. While thick bulk diodes exhibit low excess noise from electron initiated multiplication, owing to the large α/β ratio (1/k), the excess noise of diodes with ω < 0.31 μm were found to be greatly reduced by the effects of dead space. The thinnest diodes exhibit very low excess noise, corresponding to k = 0.08, up to a multiplication value of 90. In contrast to most III-V materials, it was found that both thick and thin Al0.8Ga0.2As multiplication layers can give very low excess noise and that electrons must initiate multiplication to minimize excess noise, even in thin structure

Modification of tumour blood flow using the hypertensive agent, angiotensin II

The effects of different doses of angiotensin II (0.02 to 0.5 microgram kg-1 min-1 on mean arterial blood pressure, tissue blood flow and tissue vascular resistance were investigated in BD9 rats. Blood flow was measured using the uptake of 125I- or 14C-labelled iodoantipyrine (125I-IAP and 14C-IAP). Spatial heterogeneity of blood flow within tumours, before and after angiotensin II infusion, was also measured using 14C-IAP and an autoradiographic procedure. Mean arterial blood pressure rose steeply with angiotensin II dose. Blood flow to skeletal muscle, skin overlying the tumour, contralateral skin, small intestine and kidney tended to decline in a dose-dependent manner. Blood flow to the tumour was also reduced (to 80% of control values) but there was no dose response. Blood flow to the heart was slightly increased and blood flow to the brain was unaffected by angiotensin II. Vascular resistance, in all tissues, was increased by angiotensin II infusion. The increase in tumour tissue was similar to that found in skeletal muscle and small intestine and is likely to be caused by a direct vasoconstricting effect of the drug rather than autoregulation of tumour blood flow in the face of an increase in perfusion pressure. The reduction in overall blood flow at the highest perfusion pressure was due to a preferential effect of angiotensin II at the tumour periphery. These results show that some tumours, at least, can respond directly to the effects of vasoactive agents

The response of tumour vasculature to angiotensin II revealed by its systemic and local administration to 'tissue-isolated' tumours.

A tissue-isolated preparation of the P22 rat carcinosarcoma was used to investigate the tumour vascular response to angiotensin II (ATII). In particular, the relative importance of systemic and local tumour factors was assessed by comparing tumour vascular resistance during systemic administration of ATII and during administration directly into the tumour-supplying artery. The effect of hypervolaemia on tumour vascular resistance was determined as well as the effect of ATII on oxygen metabolism. Tumour vascular resistance was increased by ATII in a dose-dependent manner. The response was biphasic with an initial peak in resistance followed by a lower plateau phase. Systemic administration of ATII was more effective in increasing tumour vascular resistance than direct administration. This suggests that systemic administration is not causing any reopening of previously collapsed tumour blood vessels. Further evidence for this is that hypervolaemia caused no reduction in tumour vascular resistance and that there was no difference in oxygen extraction by tumours between groups treated with systemically and directly administered ATII. A heterogeneous distribution of ATII receptors in the P22 tumour is a more likely explanation for the known heterogeneity of blood flow response to ATII

Persistence of perennial ryegrass, tall fescue and cocksfoot following annual sowings: Influence of grass species, ryegrass cultivar and pasture age on yield, composition and density

Persistence is an important component of perennial pasture-grass productivity. Defining traits that affect persistence is essential for improving pasture longevity through plant breeding and for identifying persistence traits that should be included in cultivar ranking indices. Compared with conventional longitudinal studies, where a single sowing is monitored over time, repeated annual sowings allow the effects on persistence of sowing year and the ensuing interactions between environment and age of pasture to be identified. An experiment was commenced in 2015 under sheep grazing in Canterbury and in 2016 under cattle grazing in Waikato, where eight cultivars of perennial ryegrass representing different ploidy, flowering date, and cultivar age (release date), and one cultivar each of tall fescue and cocksfoot were sown in four randomised complete blocks in autumn each year. This paper reports interim data on spring and autumn pasture yield, composition, and density of 3-year-old, 2-year-old and 1-year-old pastures exposed to the same environmental conditions within the same, single year. There were significant effects on yield, botanical composition, basal cover and tiller density due to cultivar, pasture age, and their interaction. When the confounding effect of year-to-year variation was removed by comparing each age cohort in the same year, the underlying differences among grass species and cultivars, and ages of pasture, is starting to reveal the nature of this influence on pasture persistence

The Fermi surface of CeCoIn5: dHvA

Measurements of the de Haas - van Alphen effect in the normal state of the heavy Fermion superconductor CeCoIn5 have been carried out using a torque cantilever at temperatures ranging from 20 to 500 mK and in fields up to 18 tesla. Angular dependent measurements of the extremal Fermi surface areas reveal a more extreme two dimensional sheet than is found in either CeRhIn5 or CeIrIn5. The effective masses of the measured frequencies range from 9 to 20 m*/m0.Comment: 4 pages, 2 figures, submitted to PRB Rapid

Measuring Red Blood Cell Velocity with a Keyhole Tracking Algorithm

A tracking algorithm is proposed to measure the velocity of red blood cells traveling through microvessels of tumors growing in skin flaps implanted on mice. The tracking is based on a keyhole model that describes the probable movement of a segmented cell between contiguous frames in a video sequence. When a history of movements exists, past, present and a predicted landing position define two regions of probability with a keyhole shape. This keyhole is used to de- termine if cells in contiguous frames should be linked to form tracks. Pre-processing segments cells from background and post-processing joins tracks and discards links that could have been formed due to noise or uncertainty. The algorithm pre- sents several advantages over traditional methods such as kymographs or particle image velocimetry: manual interven- tion is restricted to the thresholding, several vessels can be analyzed simultaneously, algorithm is robust to noise and a wealth of statistical measures can be obtained. Two tumors with different geometries were analyzed; average velocities were 211±136 [μm/s] (mean±std) with a range 15.9-797 [μm/s], and 89±62 [μm/s] with a range 5.5-300 [μm/s] respec- tively, which are consistent with previous results in the litera- ture

Signaling interactions between RhoGTPase and cAMP/cGMP influence endothelial responses to the vascular disrupting agent combretastatin A4 phosphate

Background: Combretastatin A4 phosphate (CA4P) is a tumour vascular disrupting agent (VDA) that targets endothelial microtubules, triggering remodelling of the actin cytoskeleton, contractility and disruption of VE-cadherin junctions through RhoGTPase/ROCK-dependent pathways. These events lead to a rise in endothelial monolayer permeability. A rise in permeability is considered crucial for vascular shutdown elicited by CA4P in vivo. CA4P also inhibits endothelial migration and induces mitotic arrest and apoptosis, so potentially it could also target tumour angiogenesis. Method: In this study, the nature of signalling interactions between Rho/ROCK and cAMP/cGMP and their influence on cytoskeletal and functional responses of endothelial cells to CA4P were investigated. Results: Several cAMP/cGMP analogues inhibited CA4P-induced Rho/ROCK activation and prevented actin remodeling, disruption of cell-to-cell junctions and permeability rise in endothelial monolayers. cAMP inhibits Rho by either protein kinase A (PKA)-dependent mechanisms or via activation of Epac1/Rap1. O-Me-cAMP, an analogue that selectively activates Epac1/Rap1 abolished activation of Rho/ROCK by CA4P while selective PKA activator 6-Bnz-cAMP only partially inhibited Rho/ROCK activation and actin remodelling by CA4P. Inhibitors of PKA did not alter endothelial responses to CA4P in the presence of cAMP analogues suggesting that cAMP acts primarily via Epac1/Rap1 to inhibit Rho/CA4P interactions. CA-4-P also inhibited endothelial migration and abolished lamellipodia at the leading edge of migrating cells in injured monolayers. Rho inhibitor C3 exoenzyme and ROCK inhibitor Y27632 as well as cAMP analogues re-established cell movement and formation of lamellipodia in wounded monolayers exposed to CA-4-P, suggesting that inhibitory effects on migration were mediated via Rho/ROCK. Conclusion: Deciphering molecular pathways that modulate endothelial responses to VDAs is important for further targeting. Our data demonstrate that interactions between cGMP/cAMP and Rho influence both the vascular disrupting and anti-angiogenic activities of CA-4-P and point to cAMP/cGMP as potential targets for improving VDA activity. Acknowledgements Funded by Cancer Research U