A framework for evaluation of on-farm mastitis diagnostics in Australia

Numerous culture-based diagnostics are available on the Australian and international markets for on-farm detection of bacterial pathogens in milk. Use of such diagnostics may provide an opportunity to improve the prudent use of antimicrobials in udder health management. Farms are low-resource settings in terms of diagnostic microbiology capacity. The World Health Organisation has identified criteria for the evaluation of diagnostic tests in low resource settings based on Accuracy, Sensitivity, Specificity, User-friendliness, being Rapid or Robust, Equipment-free and being Deliverable (ASSURED). Here, we review how those criteria can be interpreted in the context of microbiological diagnosis of mastitis pathogens, and how on-farm diagnostics that are currently available in Australia perform relative to ASSURED criteria. This evaluation identifies multiple trade-offs, both with regard to scientific criteria and with regards to convenience criteria. More importantly, the purpose of testing may differ between farms, and test performance should be evaluated relative to its intended use. The ability of on-farm mastitis diagnostics to inform mastitis treatment decision-making in a timely and cost-effective manner depends not just on test characteristics but also on farm-specific pathogen prevalence, and on the farm enterprise's priorities and the farm manager's potential courses of action. With most assay evaluations to date conducted in professional laboratories, there is a surprising dearth of information on how well any of the diagnostic tests perform on-farm and, indeed, of the on-farm decision-making processes that they aim to inform.     

Image processing-based study of soil porosity and its effect on water movement through Andosol intact columns

The soil pore network and marcoporosity are important factors affecting water and solute transport. The transfer of contaminants to water resources is of particular importance in the Valle de Bravo watershed as it provides 10% of the drinking water for the 20 million inhabitants of Mexico City. This watershed is composed mainly of Andosols with unique mineralogical and physical characteristics. Soil porosity is usually examined on thin sections, using various image analysis techniques. We propose a novel methodology combining image analysis and a displacement experiment to study relationships between soil structure and water tracer transport parameters. H₂¹⁸O displacement experiments were conducted through intact soil columns sampled at three depths from a representative cultivated Andosol profile. The soil structure and pore characteristics were obtained by image analysis on thin sections obtained from each column at the end of the displacement experiment. The total 2D porosity (for pores larger than 50 μm) varied from 80% of the total section area in the topsoil to around 60% in the subsoil. Tubular pores were the most abundant in the soil profile, but ploughing of the topsoil had destroyed sections of these pores and replaced them with packing pores. Water transport in the intact subsoil columns was always in physical non-equilibrium, showing the existence of preferential flow pathways. In the topsoil, one column out of three showed no preferential flow, demonstrating that soil ploughing also homogenised pore connections. Pore connectivity was larger in the ploughed topsoil than in their deeper soil horizon counterparts. Our methodology offers a 2D quantitative characterisation of the macroporous network at 50 μm resolution and the determination of water transport parameters on the same intact soil samples. 3D characterisation of soil porosity using X-ray computed tomography (CT) gives a better picture of pore connection but usually has lower spatial resolution and a larger cost.     

Plants as de-worming agents of livestock in the Nordic countries: historical perspective, popular beliefs and prospects for the future.

Preparations derived from plants were the original therapeutic interventions used by man to control diseases (including parasites), both within humans and livestock. Development of herbal products depended upon local botanical flora with the result that different remedies tended to develop in different parts of the world. Nevertheless, in some instances, the same or related plants were used over wide geographic regions, which also was the result of communication and/or the importation of plant material of high repute. Thus, the Nordic countries have an ancient, rich and diverse history of plant derived anthelmintic medications for human and animal use. Although some of the more commonly used herbal de-wormers were derived from imported plants, or their products, many are from endemic plants or those that thrive in the Scandinavian environment. With the advent of the modern chemotherapeutic era, and the discovery, development and marketing of a seemingly unlimited variety of highly efficacious, safe synthetic chemicals with very wide spectra of activities, herbal remedies virtually disappeared from the consciousness--at least in the Western world. This attitude is now rapidly changing. There is a widespread resurgence in natural product medication, driven by major threats posed by multi-resistant pest, or disease, organisms and the diminishing public perceptions that synthetic chemicals are the panacea to health and disease control. This review attempts to provide a comprehensive account of the depth of historical Nordic information available on herbal de-wormers, with emphasis on livestock and to provide some insights on potentially rewarding areas of "re-discovery" and scientific evaluation in this field.     

The effect of the herbicide diuron on soil microbial activity

The inhibitory effect of the herbicide diuron [3-(3,4-dichlorophenyl)-1,1-dimethylurea] on microbial activity in red Latosol soil was followed using microcalorimetry. The activity of the micro-organisms in 1.50 g of soil sample was stimulated by addition of 6.0 mg of glucose and 6.0 mg of ammonium sulfate under 35% controlled humidity at 298.15 (+/- 0.02) K. This activity was determined by power-time curves that were recorded for increasing amounts of diuron, varying from zero to 333.33 micrograms g-1 soil. An increase in the amount of diuron in soil caused a decrease of the original thermal effect, to reach a null value above 333.33 micrograms g-1 of herbicide. The power-time curve showed that the lag-phase period and peak time increased with added herbicide. The decrease of the thermal effect evolved by micro-organisms and the increase of the lag-phase period are associated with the death of microbial populations caused by diuron, which strongly affects soil microbial communities.     

Are Endocrine Disrupting Compounds a Threat to Farm Animal Health,Welfare and Productivity?

Contents The sources and characteristics of endocrine disrupting compounds (EDCs) are reviewed and discussed with respect to their potential effects on farm animal health, welfare and productivity. The importance of certain properties of these compounds in relation to the expression of their biological effects is addressed together with potential routes of exposure. It is concluded that little is known of factors affecting the tissue concentrations of EDCs in farm animals, the concentrations that are required to perturb physiological function in these species, the effects of prolonged exposure to low doses, the effect of cocktails of EDCs and other pollutants or the responses of specific organs and physiological systems that are affected by EDCs. Much of the available information pertaining to EDCs is derived from epidemiological studies of wildlife species and from laboratory animal studies and while these studies have significant limitations, they are considered to be valuable indicators of potential effects in farm animal species. The results of such studies, together with the small amounts of data from studies of ruminants, indicate that there may be significant effects of exposure to environmental levels of EDCs on farm animal health, even although effects are not generally apparent in practice, at this time.     

Herbicide resistance in Aster squamatus conferred by a less sensitive form of acetolactate synthase

A biotype of Aster squamatus (Sprengel) Hieronymus with suspected resistance to the ALS-inhibiting herbicide imazapyr was detected in a chicken farm in the province of Seville, Spain, which had been treated once a year with imazapyr for 10 years. Resistance to imazapyr in this biotype was studied using dose-response experiments, absorption and translocation assays, metabolism studies and ALS activity assays. The rate of imazapyr required to inhibit A squamatus growth by 50% (ED50) was 15 times higher for the R (resistant) than for the S (susceptible) biotype. Cross-resistance existed for the ALS-inhibitors imazamox, imazethapyr, amidosulfuron, nicosulfuron, rimsulfuron, triasulfuron and tribenuron, but not for bensulfuron. Control of A squamatus using alternative herbicides was poor with clopyralid, intermediate with quinclorac, amitrole and MCPA, and excellent with 2,4-D, glufosinate and glyphosate. Absorption of [14C]imazapyr increased over time for both the R and S biotypes, and translocation from the treated leaf to shoots and roots was similar in both biotypes, with most of the radioactivity remaining in the treated leaf. No metabolites of imazapyr were detected in either biotype. Sensitivity of the ALS enzyme (target site) to imazapyr was lower for the R biotype (I50(R) = 4.28 x I50(S)). The mechanism of imazapyr resistance in this R biotype appears to be an altered ALS conferring decreased sensitivity to imazapyr at the whole-plant level.     

Influence of exogenous gonadotropin-releasing hormone on ovarian function in beef cows after short- and long-term nutritionally induced anovulation

The effect of pulsatile infusion of gonadotropin-releasing hormone (GnRH) on follicular function was evaluated in nutritionally induced anovulatory beef cows. After 4 (short; n = 12) or 18 wk (long; n = 12) of anovulation, cows were randomly assigned within anovulatory group to either 2 microg of GnRH treatment or saline (control; i.v.) every hour for 5 d. Ovarian structures were monitored by daily ultrasonography. Growth rate of the largest follicle (P < 0.01) and maximal size of the largest follicle during treatment were greater (P < 0.01) for GnRH vs control cows. At exsanguination after 5 d of GnRH treatment, the size of the second-largest follicle was greater (P < 0.05) in short (i.e., 4 wk) anovulatory cows than in long (i.e., 18 wk) anovulatory cows and the largest follicle tended (P < 0.10) to be larger in long vs short anovulatory cows. Short anovulatory GnRH-treated cows had more small follicles than short anovulatory control cows or long anovulatory GnRH-treated or control cows (anovulation x GnRH; P < 0.10). Follicular fluid (FFL) concentrations of estradiol (P < 0.01) and androstenedione (P < 0.05) were greater in GnRH vs control cows. Concentrations of insulin-like growth factor-I were greater (P < 0.10) in large vs small follicles in cows that were anovulatory for 4 wk, but not in cows that were anovulatory for 18 wk. The amount of insulin-like growth factor-binding protein (IGFBP)-3 in FFL was greater (P < 0.05) in 4- vs 18-wk anovulatory cows. Amounts of IGFBP-2, -4, and -5 were greater (P < 0.001) in FFL of small (< 5 mm) vs large (> or = 5 mm) follicles regardless of treatment. We conclude that pulsatile treatment with GnRH for 5 d stimulates similar growth of the largest follicles in short- and long-term anovulatory beef cows, and that the duration of anovulation is not a major factor that limits follicular growth w hen anovulatory cowsare treated with GnRH. The primary intrafollicular factors associated with increased follicular size were increased concentrations of estradiol, progesterone, and insulin-like growth factor-I,and decreased concentrations of IGFBP-2, -4, and -5. Increased duration of anovulation was associated with decreased concentrations of IGF-I and IGFBP-3 in FFL.     

Effects of intraovarian infusion of insulin-like growth factor-I on ovarian follicular function in cattle

The objective of this study was to determine if increased secretion of intraovarian insulin-like growth factor-I (IGF-I), experimentally induced via minipumps, affects follicular function in cattle. Fourteen cycling Holstein cows were divided equally into two groups: Control, osmotic minipumps (containing vehicle) surgically inserted into each ovary, or IGF-I treated, osmotic minipumps as in Controls but pumping 2.0 microg of recombinant human IGF-I per hr for 7 days. All cows were synchronized with prostaglandin F(2alpha) 0.10) between Control and IGF-I-treated cows during Days 2 to 6 of treatment. IGF-I treatment increased (P<0.05) estradiol concentrations in follicular fluid of small follicles, but had no effect (P<0.10) on estradiol concentrations in follicular fluid of large follicles, or on progesterone, androstenedione, or IGF binding protein concentrations in small or large follicles. We conclude that a 7-day infusion of IGF-I directly into the stroma of the ovary altered follicular growth and follicular fluid estradiol concentrations.