Models of kleptoparasitism on networks: the effect of population structure on food stealing behaviour

The behaviour of populations consisting of animals that interact with each other for their survival and reproduction is usually investigated assuming homogeneity amongst the animals. However, real populations are non-homogeneous. We focus on an established model of kleptoparasitism and investigate whether and how much population heterogeneities can affect the behaviour of kleptoparasitic populations. We consider a situation where animals can either discover food items by themselves or attempt to steal the food already discovered by other animals through aggressive interactions. Representing the likely interactions between animals by a network, we develop pairwise and individual-based models to describe heterogeneities in both the population structure and other individual characteristics, including searching and fighting abilities. For each of the models developed we derive analytic solutions at the steady state. The high accuracy of the solutions is shown in various examples of populations with different degrees of heterogeneity. We observe that highly heterogeneous structures can significantly affect the food intake rate and therefore the fitness of animals. In particular, the more highly connected animals engage in more conflicts, and have a reduced food consumption rate compared to poorly connected animals. Further, for equivalent average level of connectedness, the average consumption rate of a population with heterogeneous structure can be higher

Role of rodents in transmission of Salmonella and Campylobacter

Salmonella and Campylobacter are generally regarded as the most important food-borne pathogens in the world. Reduction or elimination of these pathogens in the first part of the food chain (on the farm) is important to prevent disease among consumers of animal products. In organic farming, elimination becomes more difficult, as food animals are allowed outdoors and have easy access to potential sources of hazardous pathogens. Whilst rodents are often associated by organic farmers with infrastructural damage and eating or spoiling of stored feed and products, their zoonotic risks are frequently underestimated. They can amplify the number of pathogens in the environment and transfer them to food animals. Thus organic farmers should be aware of the need for rodent control from a food safety perspective. Preferably, rodent control should form an integral part of a total package of hygiene measures to prevent transfer of food-borne pathogens. These should also include e.g. control of wild birds and flies and obligatory disinfection of boots/clothes and equipment for farm workers and visitors

Female and male Wistar rats (Rattus norvegicus) discriminate diets according to energetic quantity

The food choice of animals is influenced by several factors including the quantity and nutrients available. It is not known, however, whether faced with alternatives that present the same amount of food, with similar flavor and obtained with the same response cost, rats would discriminate between diets with different energetic quantities. The aim was to verify whether female and male Wistar rats (Rattus norvegicus) discriminate between three types of food that differ in their energetic content (whether or not they prefer one) and whether the flavor could affect the choice between two diets with equal energetic quantities. Twelve Wistar rats (six of each sex) underwent tests of choice between pairs of diets of different energetic values. After the tests, the animals had at their disposal, in the home cage, two diets with the same energetic content, which differed in flavor (one contained sucrose) - Flavor test. The consumption of each diet was measured for five consecutive days. All the subjects demonstrated a preference for the more energetic alternative, regardless of the combination of diets presented. In the Flavor test the animals did not show significant preference for any diet, i.e., the consumption of both the S and N diets were statistically equal for all subjects. It was concluded that the animals, regardless of sex, discriminated between the diets with different energetic values and that the flavor did not seem to be a determinant variable in the food choice.

Emerg. Infect. Dis

The multidrug-resistant (MDR) Salmonella enterica serotype Newport strain that produces CMY-2 β-lactamase(Newport MDR-AmpC) was the source of sporadic cases and outbreaks in humans in France during 2000–2005. Because this strain was not detected in food animals, it was most likely introduced into France through imported food products

Resistance to carbapenems in non-typhoidal Salmonella enterica serovars from humans, animals and food

Non-typhoidal serovars of Salmonella enterica (NTS) are a leading cause of food-borne disease in animals and humans worldwide. Like other zoonotic bacteria, NTS have the potential to act as reservoirs and vehicles for the transmission of antimicrobial drug resistance in different settings. Of particular concern is the resistance to critical “last resort” antimicrobials, such as carbapenems. In contrast to other Enterobacteriaceae (e.g., Klebsiella pneumoniae, Escherichia coli, and Enterobacter, which are major nosocomial pathogens affecting debilitated and immunocompromised patients), carbapenem resistance is still very rare in NTS. Nevertheless, it has already been detected in isolates recovered from humans, companion animals, livestock, wild animals, and food. Five carbapenemases with major clinical importance—namely KPC (Klebsiella pneumoniae carbapenemase) (class A), IMP (imipenemase), NDM (New Delhi metallo-β-lactamase), VIM (Verona integron-encoded metallo-β-lactamase) (class B), and OXA-48 (oxacillinase, class D)—have been reported in NTS. Carbapenem resistance due to the production of extended spectrum- or AmpC β-lactamases combined with porin loss has also been detected in NTS. Horizontal gene transfer of carbapenemase-encoding genes (which are frequently located on self-transferable plasmids), together with co- and cross-selective adaptations, could have been involved in the development of carbapenem resistance by NTS. Once acquired by a zoonotic bacterium, resistance can be transmitted from humans to animals and from animals to humans through the food chain. Continuous surveillance of resistance to these “last resort” antibiotics is required to establish possible links between reservoirs and to limit the bidirectional transfer of the encoding genes between S. enterica and other commensal or pathogenic bacteria

Comparison of a Calan gate and a conventional feed barrier system for dairy cows: feed intake and cow behaviour

peer-reviewedThere is little published information on comparisons of individual and group feeding systems for dairy cows. Twenty-four dairy cows were used in a three-period incompletely balanced, change-over design study, to examine food intake and feeding behaviour of dairy cows offered their food via group-access electronic Calan gates, or via a conventional feed-barrier system. The food offered was in the form of a complete diet, and comprised grass silage and concentrates (60:40 dry matter (DM) basis). With the conventional feed-barrier system a maximum of eight animals were able to feed at any one time, while the Calan-gate system allowed a maximum of three animals to feed at any one time. Method of offering the ration had no effect on daily DM intake. During the 8-h period after animals were given access to fresh food, the mean number of animals feeding at any one time was 5.4 and 3.0 for the conventional and Calan-gate systems, respectively, while total intake over this period was 11.0 and 9.2 kg DM per cow, respectively. When access to feed was restricted by the use of Calan gates, animals responded by increasing their intake rate. It is concluded that total DM intake was unaffected by the use of a group Calan-gate feeding system as animals modified their feeding behaviour to maintain food intake

Food supply chain consequences of new responses to livestock epidemics

This article studies supply chain consequences from applying the new-more socially acceptable -strategy of emergency vaccination instead of the large-scale killing of healthy animals for controlling livestock epidemics. We consider an outbreak of foot and mouth disease in a densely populated livestock area of the Netherlands. From an epidemiological perspective, simulation results show that emergency vaccination significantly reduces the size of an epidemic, both in terms of the length of an outbreak and in the number of animals killed. However, in a worst-case situation, not destroying the vaccinated animals after the end of the epidemic leads to additional consequential losses for food supply chains involved of about Euro 200 million. A business case illustrates that the exact size of these losses depends on specific supply volumes and marketing strategies. Calculations provide a basis for addressing cost sharing issues and loss reducing opportunities of new responses to livestock epidemics.livestock epidemics, financial impact, consumer acceptance, Food Consumption/Nutrition/Food Safety,