Sheep blowfly strike: the cost of control in relation to risk

Sheep blowfly strike (ovine cutaneous myiasis) is a widespread economic and welfare problem in sheep husbandry in many parts of the world. Strike incidence is determined by a complex interaction of fly abundance, host susceptibility and climate, combined with farmer husbandry and intervention strategies. Sheep farmers adopt a range of approaches to the type and timing of the management used for the control of blowfly strike, the rational basis for which is often not robust. Here a deterministic model, based on existing data relating to fly abundance, seasonal risk and strike incidence, is used to compare the variable costs associated with different strike management strategies. The model shows that not employing prophylactic treatment is the lowest cost strategy only where strike risk is low. In all other circumstances, prophylactic treatment incurs lower costs than not doing so, because the deaths associated with strike outweigh the costs of prophylactic treatment. Lamb treatment, in particular, has a substantial effect on strike and cost reduction, since lambs are the most abundant age-class of animals and are at the highest risk over the period when fly abundance is the greatest. Early-season treatment of ewes before shearing is also an important component of the lowest cost strategies, particularly when the blowfly season is extended. While the rational choice of the most appropriate strike management strategy is essential in the context of farm economics, welfare considerations lend added importance to treatment decisions that reduce strike incidence.     

Unravelling the physical,technological and economic factors driving the intensification trajectories of livestock systems

Over the past 100 years, the French livestock sector has experienced significant intensification that has occurred in different ways across the country. Specifically, France has changed from a homogeneous state with most of the agricultural area covered by grasslands and a uniform distribution of animals, to a heterogeneous state characterised by an uneven distribution of grasslands, livestock numbers and livestock species. Studying the dynamics of this change is fundamental to the identification of drivers that shaped the various intensification trajectories and led to these different states, as well as to the prediction of future changes. Hence, the objective of this study was to characterise the trajectories undertaken by the French livestock sector to understand the intensification process and the role of socioeconomic, land use and production-related factors. A set of 10 indicators was employed to analyse the main changes between 1938 and 2010, using principal component analysis followed by a clustering of the 88 French departments. Between 1938 and 2010, significant increases in farm size, mechanisation, labour productivity and the stocking rates of monogastrics enabled the French livestock sector to double its production. The most important changes involved mechanisation (with the number of tractors per hectare (ha) rising from 0.0012 to 0.0053), labour productivity (improving from 8.6 to 35.9 ha/worker), livestock production (e.g. milk production increasing from 758 to 1856 l/ha of fodder area) and stocking rates (rising from 0.57 to 0.98 livestock units (LU) per ha). The increased heterogeneity apparent in the patterns of change throughout France’s departments was captured by clustering four trajectories. Two trajectories were formed by departments that experienced strong specialisation towards livestock production, with one type mainly orientated towards high-intensive dairy, poultry and pig landless production systems, and a second type orientated towards extensive beef grazing production systems. Another trajectory corresponded to departments that specialised in crop production with high labour productivity; mixed crop-livestock systems were still maintained at the margins of this group of departments. The fourth trajectory corresponded to the lowest livestock population and productivity levels. The increase in mechanisation during the period was important but uniform, with no significant differences between the trajectories. This typology of intensification trajectories will enable the targeting of specific areas in which the detrimental impacts of livestock intensification require mitigation and provide guidance for future livestock sector developments.     

Lethal and sub‐lethal effects of faecal deltamethrin residues on dung‐feeding insects

Endectocides administered to livestock to facilitate pest and parasite control may be excreted in the faeces at concentrations that are toxic to coprophagous insects, including species of ecological importance. Although much research has focused on the effects of macrocyclic lactones, relatively less attention has been given to any similar impacts of the widely used pyrethroid insecticides. Here, the effects of faecal residues of the pyrethroid deltamethrin after application to Holstein–Friesian cattle in a proprietary pour‐on formulation are examined. Freshly dropped dung was collected 1, 3, 5 and 7 days after treatment and from an untreated control group. In laboratory bioasssays, female Lucilia sericata (Diptera: Calliphoridae) blow flies matured significantly smaller egg batches and had a lower percentage of eggs hatch after feeding on dung collected for up to 5 days after treatment, compared with flies feeding on dung from untreated cattle. In the field, artificial dung pats were constructed from the collected dung and left on pastureland for 7 days before being retrieved and searched for insects. Significantly more adult Diptera emerged from the faeces of untreated cattle than from the dung of treated cattle collected on days 1 and 3 after treatment. Adult Coleoptera were found in lower numbers in the dung of treated animals compared with control dung, suggesting a repellent effect. The results indicate that deltamethrin residues in cattle faeces have a range of lethal and sub‐lethal effects on dung‐feeding insects for up to a week after treatment, but that the precise duration and nature of toxicity varies depending on the sensitivity of the insect in question.     

Genome‐wide differential DNA methylation in tropically adapted Creole cattle and their Iberian ancestors

Enhancing climate resilience and sustainable production for animals in harsh environments are important goals for the livestock industry given the predicted impacts of climate change. Rapid adaptation to extreme climatic conditions has already been imposed on livestock species, including those exported after Columbus's arrival in the Americas. We compared the methylomes of two Creole cattle breeds living in tropical environments with their putative Spanish ancestors to understand the epigenetic mechanisms underlying rapid adaptation of a domestic species to a new and more physiologically challenging environment. Reduced representation bisulfite sequencing was used to assess differences in methylation in Creole and Spanish samples and revealed 334 differentially methylated regions using high stringency parameters (P‐value <0.01, ≥4 CpGs within a distance of 200 bp, mean methylation difference >25%) annotated to 263 unique features. Gene ontology analysis revealed candidate genes involved in tropical adaptation processes, including genes differentially hyper‐ or hypomethylated above 80% in Creole samples displaying biological functions related to immune response (IRF6, PTGDR, FAM19A5, PGLYRP1), nervous system (GBX2, NKX2‐8, RPGR), energy management (BTD), heat resistance (CYB561) and skin and coat attributes (LGR6). Our results entail that major environmental changes imposed on Creole cattle have had an impact on their methylomes measurable today, which affects genes implicated in important pathways for adaptation. Although further work is needed, this first characterization of methylation patterns driven by profound environmental change provides a valuable pointer for the identification of biomarkers of resilience for improved cattle performance and welfare under predicted climatic change models.