Animal health in a changing world: the relationship between animals, humans and the environment

Wageningen University & Research (WUR) conducts extensive research on both animal diseases and overall animal health. Our scientists tackle the prevention of disease and the spread of pathogens from multiple perspectives, benefiting animals, humans and the environment. This ranges from biological research at the individual animal level to studies on disease transmission at the population level. Their work covers everything from practical knowledge of barn systems to hygiene protocols for optimal biosecurity.

This article outlines our animal health research from three perspectives:

1. Preventing outbreaks and disease in animals
2. Mitigating the impact if animals do become ill unexpectedly
3. Promoting recovery

Research associate Ingrid van Dixhoorn is an expert on preventive animal health. Her research focuses on animal resilience. “Resilient animals have the ability to cope with various disruptions, allowing them to remain healthy or, if disease does occur, to recover quickly.” Van Dixhoorn’s research has included studying the transition period from dry-off to lactation in cows. “Cows are vulnerable during the first two weeks of this period,” she explains. “They can become much more resilient if we support their day-night rhythm, create stable groups and ensure adequate feed intake.”

Resilient animals

Research conducted at Wageningen has found that resilience can be improved in pigs. One way to do this is environmental enrichment in the barn, using a variety of materials that allow pigs to express more of their natural behaviour, such as rooting and chewing. “Pigs living in an enriched barn have a different immune system and that means they are less susceptible to disease and can recover more quickly,” says Van Dixhoorn. "In our study, pigs in an enriched barn were found to have fewer lung infections. Animals that did get sick recovered significantly faster.”

Genetic factors and animal health

Besides environmental factors, genetic factors also play an important role in animal resilience and robustness. According to Mario Calus, professor of breeding and genomics, farmers want to be able to milk healthy cows with minimal labour costs, and breeding has been based on that idea for more than 20 years now. “We can determine breeding values very precisely,” says Calus. “For example, when assessing the predisposition to udder infection, we look at the animal’s performance as well as that of its immediate family, such as parents and offspring. Genetic selection through DNA analysis is also a promising way of determining and improving disease resistance, for example.”

Until recently, selecting for reduced susceptibility to infection simply meant identifying whether an animal became infected or not. But infections in populations are actually transmitted from animal to animal. “That’s why we are now also looking at the degree of infectiousness,” says professor Calus. “The potential of genetic selection to reduce the impact of infectious diseases in livestock herds is therefore suddenly much greater than previously thought.”

Interaction with the environment

Besides genetic predisposition, animal health is strongly influenced by the way animals interact with the environment and any pathogens present. Wageningen University & Research studies the interactions between animals, humans and the environment.

“Animals’ habitats are changing,” says Van Dixhoorn. “Groundwater levels are being raised in peat-soil pastureland to reduce land subsidence and greenhouse gas emissions. Water logging also poses risks. These risks include the rise of parasites – such as liver fluke, transmitted by snails – and the emergence of plants that are harmful to animals,” she explains. Wageningen’s researchers are looking at how to manage the risks posed by pathogens and poisonous plants. “For liver fluke, we’re looking at how we could naturally interrupt the cycle of the liver fluke parasite to reduce the levels of infections in cows. Herbs or greater dietary diversity might boost the immunity and overall

Preventing infection

Avian influenza is another area where efforts are being made to determine how the pathogen, in this case a virus, can be kept away from livestock. “In the autumn, wild birds bring the avian influenza virus to Europe along migration routes from breeding grounds in northern Siberia, for example. Droppings from infected wild birds end up everywhere in the environment, including the yards of poultry farms, for example,” explains epidemiologist Armin Elbers. Wageningen University & Research is conducting research into how the virus travels from those infected environments into poultry sheds. “There is still a lot of uncertainty about this.”

Activity is a good indicator of animal welfare and health and provides farmers with indicators so that they can intervene quickly to reduce the impact of disease, says Malou van der Sluis, a research associate in breeding and genomics. “In our study, we monitored chickens by placing a small sensor on their leg. Antennas in the floor registered the sensors, so that we could track the movements of each chicken.”

Van der Sluis investigated whether there were any links between activity, body weight and leg health. “Chicks with a lower body weight are on average more active than heavier chicks of the same age.” Leg health also affects activity. According to Van der Sluis, tracking chicks in this way opens up opportunities for breeders to select for activity and leg health. “At the same time, it is important to avoid any negative side effects of genetic selection. Active chicks might also be anxious chicks that are easily startled and cause turmoil in the barn.”

Van der Sluis says it’s also important to intervene promptly to prevent negative health effects when, for example, temperatures are high. “In prolonged hot weather, chicks drink more and eat less. They pant, spread their wings and become less active. If poultry farmers monitor this automatically, they can spot it faster and take appropriate action if necessary. That’s better for the chicks and also prevents a loss of productivity.”

Early diagnostics

When the presence of a pathogen is suspected, early diagnostics can also be crucial to limiting the impact of disease. WUR has a large range of diagnostic tests for disease detection (including notifiable diseases) and export diagnostics. Researchers are also developing new tests, for example for udder infections in cows. Making on-site diagnoses is a new development, using dipsticks or a test similar to the rapid COVID-19 test. These tests provide access to quick diagnostics and enable farmers and vets to respond more quickly.

Intestinal health plays a major role in the overall health of animals. The gut supplies animals with nutrients and plays a major role in the development of an animal’s immune system and general resilience. Gut bacteria (the microbiome) play a major role in both processes.

“The microbiome is a community of microorganisms, such as bacteria, fungi and viruses, living in a particular environment. Like humans, animals have a variety of microbiomes, for example on the skin, in the mouth, lungs and intestines,” says senior scientist Dirkjan Schokker. According to Schokker, the gut microbiome is an important factor in achieving good gut health, and for the development and functioning of the immune system. The balance of the gut microbiome can be disrupted by disease, stress, or change of feed. Animals with a resilient microbiome will be able to cope with disruptions or quickly restore the balance where necessary.

Barn management

Barn management can play a role in making the microbiome more resilient. “If animals are able to express more of their natural behaviour, such as being free to root around in the mud more, this will have a positive effect on the microbiome. Environmental enrichment not only improves the welfare of pigs, but also supports the development of their immune system and gut health, which can help reduce antibiotic use,” says Schokker.

Animal nutrition

“Problems with digestion can have serious consequences,” says Wouter Hendriks, professor of animal nutrition. “If a horse has difficulty digesting grass sugars and starch, painful inflammation can develop in the hoof. And broiler chicks that appear healthy may not grow as much if they have mild inflammatory reactions in their gut,” he explains. “It’s therefore important to ensure good gut health and optimal nutrient utilisation. That’s good for the immune system, welfare and growth. A healthy gut also ensures that animals emit fewer pollutants, which is good for the environment.”

But Hendriks warns that measures designed to support health and resilience aren’t always compatible with other objectives in animal husbandry. “Efforts are being made to reduce nitrogen emissions as a way of reducing the environmental impact of animal husbandry. One of the tools available to manage this is the lowering of protein content in feeds. But our research shows that pigs bite each other more when they get too little protein,” he explains. Providing extra chewing and rooting material can prevent this behaviour within a few weeks.“A better option appears to be the addition of amino acids that compensate for the lack of protein. That solves the biting problem.”

Animal health research at Wageningen University & Research focuses in part on acquiring knowledge of animal diseases and applying that knowledge to prevent their occurrence and spread, control the pathogen and/or limit the effects of the illness in both animals and humans.

Despite efforts to enhance the resilience of animals and support their immune systems, infectious diseases can still make an individual animal or a group of animals seriously ill. Depending on the pathogen, the use of drugs may then be necessary. Wageningen University & Research also tests the effectiveness of those drugs. For example, research has been done into the efficacy of avian influenza vaccines and bluetongue vaccines vaccines.

Vaccines are commonly used to prevent animals from becoming infected and going on to infect other animals when they are exposed to a specific pathogen. This can prevent or contain outbreaks within and between groups. A vaccine activates the body’s own immune system at an early stage, so that the immune system immediately becomes active as soon as the pathogen enters the body.

Antibiotics are used to combat bacterial diseases. Antibiotics are very effective in fighting bacterial infection and restoring health in both humans and animals. However, some pathogenic bacteria have evolved in such a way that they have become insensitive to antibiotics. This makes infections more difficult to treat. This poses a threat not only to animals, but also to humans because antibiotic resistance can sometimes be passed on.