To treat or not to treat: diagnostic thresholds in subclinical helminth infections of cattle

Helminth infections of cattle place significant burdens on livestock production and farm economic efficiency. Heavy infections are relatively easy to detect and treat with anthelmintics. However, subclinical infections have major but often hidden impacts on animals, necessitating more refined diagnostics to detect them and ideally inform farmers about the likely impact of anthelmintic treatment on animal and herd performance. Here, we review recent advances in diagnosing three major cattle helminth infections – gastrointestinal nematodes (GINs), liver flukes, and lungworms – and the search for subclinical infection thresholds to guide treatment decisions. Combining refined diagnostic thresholds with farm-specific information on grazing systems and animal history enables farmers to tailor helminth treatments to specific epidemiological circumstances, thereby limiting anthelmintic resistance (AR) and boosting agricultural efficiency and food security.     

To meet or not to meet welfare outcome thresholds: a case-control study in dairy cow herds

Recently published thresholds allow classifying dairy cattle herds according to target, caution and alert ranges for welfare outcomes. Such normative thresholds provide one way to transparently assess production practices and are a straightforward communication tool with farmers. In an ordinal response case-control study, we investigated associations of animal, management and resource-related indicators with the risk of exceeding thresholds of prevalence for lameness, claw disorders, integument alterations and leg cleanliness. To this end, we used cumulative logistic regression models on 264 tethered and 392 loose-housed Austrian dairy herds. In tethered herds, the risk indicator average lactation milk yield was positively associated with the probability to exceed thresholds for integument alteration prevalence but negatively regarding leg cleanliness. Associations were also found for operation type regarding integument alterations (lower risk on organic vs conventional farms), for herd size regarding lameness (negative association) and dirty upper hind leg (positive association), and for percentage of fifth or higher parity cows in the herd regarding dirty lower hind leg (positive association). Stall type was identified as risk indicator regarding claw disorders (lower risk of long vs short stands). In loose housing systems, none of the analysed risk indicators was associated with the probability to exceed thresholds for total lameness and claw disorder prevalence. Negative associations with the probability to exceed caution or alert thresholds were identified for lifetime milk yield (dirty upper hind leg), lactation milk yield (dirty upper and lower hind leg), percentage of cows in the herd with a fat-protein-ratio <1 (integument alterations), and percentage of cows in the herd with a fat-protein-ratio >1.5 (dirty upper hind leg). Pasture access showed negative (severe lameness, integument alterations) and herd size positive associations (severe lameness) with the probability to exceed thresholds. Deep litter cubicles compared to raised cubicles with rubber mats showed a lower probability to exceed thresholds (integument alterations, dirty lower hind leg) as well as solid rubber compared to concrete slatted flooring in alleyways (integument alterations). Assessments carried out during the pasture period compared to during winter housing were associated with a lower risk of exceeding thresholds for leg cleanliness measures in both, tethered and loose-housed herds, and for integument alteration prevalence in tethered herds. In conclusion, no principal risk indicator was identified which consistently determined the probability of exceeding predefined thresholds of considered welfare outcomes. Nevertheless, outcome-specific factors show sufficient impact on the categorisation of farms according to prevalence ranges.     

To be or not to be--determinants of embryonic survival following heat shock

Elevated temperature can reduce developmental competence of the preimplantation embryo. Whether an embryo survives elevated temperature depends on its genotype, stage of development, exposure to regulatory molecules and redox status. Following fertilization, the embryo is very sensitive to heat shock. By Days 4-5 after insemination, however, the embryo has acquired increased resistance to elevated temperature. One system that may potentiate embryonic survival at later stages of embryonic development is the apoptosis response-inhibition of apoptosis responses at Day 4 exacerbated effects of heat shock on development. Embryo responses to heat shock at Days 4-5 also depend upon genotype because Bos indicus embryos are more resistant than embryos from non-adapted B. taurus. Some experiments (although not all) indicate that survival following heat shock can be increased by reducing oxygen tension, suggesting involvement of reactive oxygen species or hypoxia-induced factors. Embryonic responses to heat shock are also affected by regulatory molecules that act to modify cellular physiology and improve cell survival. The best characterized of these is insulin-like growth factor-1 (IGF-1). Actions of IGF-1 to allow development following heat shock are independent of its anti-apoptotic actions because inhibition of the phosphatidylinositol-3 kinase pathway through which IGF-1 blocks apoptosis does not prevent thermoprotective effects of IGF-1 on development. Identification of specific determinants of embryonic survival creates the opportunity for new strategies to improve pregnancy rates in animals exposed to heat stress. Many environmental perturbations activate similar cellular responses. Therefore, molecular and cellular systems that improve embryonic survival to heat shock may confer protection from other embryotoxic conditions.     

To compete or not to compete: an experimental study of interactions between plant species with contrasting root behaviour

Game-theoretic models predict that plants with root systems that avoid belowground competition will be displaced by plants that overproduce roots in substrate shared with competitors. Despite this, both types of root response to neighbours have been documented. We used two co-occurring clonal species (Glechoma hederacea and Fragaria vesca) with contrasting root responses to neighbours (avoidance of competition and contesting of resources, respectively) to examine whether functional variation in other traits affected the success of each rooting strategy, leading to a different outcome from that predicted on the basis of root behaviour alone. Vegetative propagation rates, morphology and biomass allocation patterns were examined when each species was challenged with competition from physically separate ramets with either the same rooting strategy (intraclonal competition) or the contrasting rooting strategy (interspecific competition). Contrary to the predictions of game-theoretic models, the species that exhibits avoidance of root competition (Glechoma) was not competitively inferior to the species that does not (Fragaria). Glechoma achieved greater total mass in the interspecific treatment than in the intraclonal treatment. However, Fragaria did not experience more intense competition from Glechoma than it did in the intraclonal treatment. Strong interference between the two species appeared to be avoided because Glechoma invested preferentially in rapid exploitation of unoccupied space, whereas Fragaria invested in increasing the competitive ability and local persistence of established ramets. Our results suggest that interspecific trade-offs between traits related to competitive ability and resource exploitation can allow coexistence of species with contrasting rooting behaviours. Full assessment of the adaptive value of different root responses to neighbours therefore requires concurrent consideration of the combined effects of a wide array of functional traits.     

A novel model for cyanobacteria bloom formation: the critical role of anoxia and ferrous iron

相似文献   

To BAC or not to BAC: marine ecogenomics

Most microbes in the ocean are still resistant to our collective cultivation efforts. Environmental microbial genomics provides science with the means for accessing and assessing the genomes, diversity, evolution and population dynamics of uncultured microorganisms--the ocean's hidden majority.     

Collecting and banking human milk: to heat or not to heat?

Data on human breast milk and its handling when fed to babies who cannot be breast-fed were reviewed to determine whether the method of processing and storage affected the properties of the milk. Breast milk is normally contaminated by potential pathogens, which seem to produce no ill effects, but it also contains antimicrobial properties which protect against infection. The evidence suggests that pasteurisation not only eliminates pathogenic bacteria but also damages bacteriostatic mechanisms, so making the milk more susceptible to later contamination. Pasteurisation also affects the nutritional properties of milk. Freezing has little effect on milk proteins, while a study on the effect of refrigeration showed that there was little bacterial growth at temperatures below 8 degrees C. Several years'' experience of feeding donated raw milk to newborn infants has confirmed that it produces no ill effects. These findings suggest that pasteurisation of donated breastmilk is unnecessary, and it is not recommended, while the decision whether or not to freeze the milk may be made on practical grounds. Raw breast milk can be safely stored at 4-6 degrees C for 72 hours.     

To be or not to be a responder in T-cell responses: ubiquitous oligopeptides in all proteins

Amino acid sequences of all proteins are essays written in the same language. Accordingly, the same set of words and phrases (oligopeptides) appear in totally unrelated proteins. The reason that only certain individuals of particular major histocompatibility complex (MHC) haplotypes can mount T-cell responses against a given antigen of pathogens is found in the fact that T-cell receptors are designed to recognize 18–20 residue-long peptide fragments sandwiched between two -helices of class I or class II MHC molecules. At this range of peptide lengths, most would appear as self, while nonselfness of the remainders are destined to be quite ambiguous, hence creating responders and nonresponders.     

To divide or not to divide: revisiting liver regeneration

The liver has a remarkable capacity to regenerate. Even with surgical removal (partial hepatectomy) of 70% of liver mass, the remnant tissue grows to recover the original mass and functions. Liver regeneration after partial hepatectomy has been studied extensively since the 19th century, establishing the long-standing model that hepatocytes, which account for most of the liver weight, proliferate to recover the original mass of the liver. The basis of this model is the fact that almost all hepatocytes undergo S phase, as shown by the incorporation of radioactive nucleotides during liver regeneration. However, DNA replication does not necessarily indicate the execution of cell division, and a possible change in hepatocyte size is not considered in the model. In addition, as 15–30% of hepatocytes in adult liver are binuclear, the difference in nuclear number may affect the mode of cell division during regeneration. Thus, the traditional model seems to be oversimplified. Recently, we developed new techniques to investigate the process of liver regeneration, and revealed interesting features of hepatocytes. In this review, we first provide a historical overview of how the widely accepted model of liver regeneration was established and then discuss some overlooked observations together with our recent findings. Finally, we describe the revised model and perspectives on liver regeneration research.     

To close or not to close: Plasmodesmata in defense

Cell death is a biological process that occurs during differentiation and maturation of certain cell types, during senescence, or as part of a defense mechanism against microbial pathogens. Intercellular coordination is thought to be necessary to restrict the spread of death signals, although little is known about how cell death is controlled at the tissue level. The recent characterization of a plasmodesmal protein, PDLP5, has revealed an important role for plasmodesmal control during salicylic acid-mediated cell death responses. Here, we discuss molecular factors that are potentially involved in PDLP5 expression, and explore possible signaling networks that PDLP5 interacts with during basal defense responses.     

To treat or not to treat: the case of tuberculosis

. Incomplete treatment of patients with infectious tuberculosis (TB) may not only lead to relapse but also to the development of antibiotic resistant TB – one of the most serious health problems facing society today. In this article, we formulate one-strain and two-strain TB models to determine possible mechanisms that may allow for the survival and spread of naturally resistant strains of TB as well as antibiotic-generated resistant strains of TB. Analysis of our models shows that non-antibiotic co-existence is possible but rare for naturally resistant strains while co-existence is almost the rule for strains that result from the lack of compliance with antibiotic treatment by TB infected individuals. Received 22 May 1995; received in revised form 28 February 1996