Recovery of intravenously infused chromium EDTA and lithium sulphate in the urine of cattle and their use as markers to measure urine volume

A series of metabolism experiments investigated the recovery of continuous-, intravenously infused chromium complexed with ethylenediamine tetra-acetic acid (CrEDTA) and lithium sulphate in the urine of cattle with a view to using the markers to estimate urine and metabolite output in grazing cattle. The recovery of Cr in urine from these infusions was similar (90%) in metabolism trials when cattle consumed three very contrasting diets: high-grain formulated pellet, lucerne hay (Medicago sativa) or low-quality native grass hay (predominantly Heteropogon contortus). By contrast, Li recovery in urine averaged 46.3 +/- 0.40% and 72.6 +/- 0.43% for native pasture and lucerne hays, respectively, but was not constant across days. There was negligible transfer of Cr from CrEDTA in blood serum to the rumen or faeces, whereas appreciable quantities of infused Li were found in both. The ratio of urine volume estimated by spot samples and marker dilution of Cr, to urine volume measured gravimetrically, was 1.05. In grazing studies using rumen-fistulated (RF) steers grazing seven different tropical and temperate grass and legume pastures, the ratio of concentrations of purine derivatives (PD) to Cr in spot samples of urine was shown to vary diurnally in the range of 49% to 157% of the average 24 h value. This finding indicated the need for regular sampling of urine to achieve an accurate average value for the PD: Cr ratio in urine for use in estimating urinary PD excretion and hence microbial protein production in the rumen. It was concluded that continuous, intravenous infusion of CrEDTA resulted in a constant recovery of Cr in the urine of cattle across diets and, provided an intensive sampling regime was followed to account for diurnal variation, it would be suitable as a marker to estimate urine volume and urinary output of PD in grazing cattle.

The biology of Australian weeds: Volume 3

Over the past decade, The biology of Australian weeds series has presented summary chapters about the biology, taxonomy, significance and control of most of Australia's most problematic weeds. Many of these chapters first appear in Plant Protection Quarterly and are then updated and revised for the book. Dane Panetta was also an editor of the second volume. This volume contains chapters of a further sixteen weed species including several of interest to Queensland.

Testing the efficacy of low volume herbicide applications on Chromolaena odorata

Siam Weed (Chromoleana odorata) is the target of an eradication program in north Queensland; however some infestations occur on ground inaccessible to high volume, ground based herbicide spray equipment. Four foliar herbicides were applied to dense infestations of mature Siam Weed in March 2009, near Townsville, north Queensland. Low volume, high concentration solutions containing 40 g L-1 a.i. glyphosate, 1.2 g L-1 a.i metsulfuron-methyl, 10 g L-1 a.i. fluroxypyr + 0.7 g L-1 a.i. aminopyralid and 15 g L-1 a.i. triclopyr + 5 g L-1 a.i. picloram + 0.4 g L-1 a.i. aminopyralid were applied using a 5 L backpack and hand gun (or splatter gun). Relatively small amounts (approximately 24-28 mL) of the high concentration solutions were applied to each bush and assessments of the replicated treated and untreated control plots were conducted 76, 207 and 356 days after treatment. These assessments demonstrated that the fluroxypyr and triclopyr based herbicides controlled 96 to 100% of plants. The metsulfuron-methyl and glyphosate based herbicides controlled 40 and 57% of plants respectively 12 months after treatment, when 3% of untreated control plants were dead. The trial demonstrated that this application method and either of two herbicides provides an additional tool for controlling Siam weed in remote areas, which are inaccessible to traditional higher volume foliar herbicide applications. Lower volume herbicide solutions reduce the volume of water and thus the effort needed to effectively treat less accessible infestations.

Refining low-volume, high-concentration herbicide applications to control Chromolaena odorata (L.) King & Robinson (Siam weed) in remote areas

Chromolaena odorata (L.) King and Robinson (Siam weed) is a highly invasive plant and a high priority for control in north Queensland. It can be effectively treated using high-volume, groundbased herbicide spray equipment, but operational information shows that this control method becomes increasingly difficult in areas where vehicle access is prevented by rougher terrain. Low-volume, high-concentration herbicide applications have proven capable of causing high mortality in these remote situations. Two trials were undertaken between May 2010 and May 2012 to refine effective rates of aminopyralid/fluroxypyr, fluroxypyr and metsulfuron-methyl, only using low-volume, high-concentration applications on Siam weed. Fluroxypyr on its own was as effective as aminopyralid/fluroxypyr as both herbicides caused 95-100% mortality at overlapping rates containing 5 to 18.85 g a.i. L-1 of fluroxypyr. Metsulfuron-methyl caused 100% mortality when applied at 3 and 6 g a.i. L-1. Effective control was achieved with approximately 16 to 22 mL of the solutions per plant, so a 5 L mixture in a backpack could treat 170 to 310 adult plants. There are several options for treating Siam weed on the ground and the choice of methods reflects the area, plant density and accessibility of the infestation. Control information from Siam weed field crews shows that low volume, high concentration herbicide applications applied using a splatter gun are a more efficient method for controlling larger, denser remote infestations than physical removal. By identifying effective herbicides that are applied through low-volume equipment, these trials provide an additional and more efficient tool for controlling Siam weed in remote areas.

Queensland Agricultural Journal Volume 13 Parts 1-6 July to December 1903

General Index Vol 13 Parts 1-6, pages 1-81