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Some practical issues for improving livestock welfare

Several areas of research are aimed directly at improving the welfare of farmed animals. These often draw upon and develop ideas, which have arisen from basic research into animal cognition, physiology and behaviour, but they are often characterised by experimental designs that simulate on-farm conditions.

Several research groups are investigating welfare issues surrounding animals’ accommodation, particularly in intensively housed pig and poultry units.


There is no simple correlation between space and welfare. It cannot be assumed that more extensive systems of management necessarily offer better welfare for an animal. For example, pigs that have been bred intensively for decades may be poorly suited to live outdoors.

The welfare pros and cons of different housing systems can be illustrated by considering egg production. There are around thirty million laying hens in the UK and currently most egg production (over 80%) comes from birds housed in battery cages. The cage system provides a highly restrictive environment that prevents hens from stretching their wings fully, exercising and performing natural behaviours such as dust-bathing and nesting. Osteoporosis (see page 45) is most severe in hens kept in battery cages because their relative inactivity accelerates loss of structural bone. Together these factors lead to abnormal behaviour and development of bone weaknesses.

Battery cages are to be banned throughout the European Union by 2012, and no new systems are now being installed. One alternative is to keep laying hens in large loose- house colony systems, where the birds are kept in barns or aviaries and may have access to the outside. Because the birds can exercise more, bone quality is improved and osteoporosis is reduced. However, mortality rates are higher than for birds kept in battery cages, and most of these deaths can be attributed to problems of aggression, fear and stress rather than disease. There can also be a high level of bone damage in birds housed in perchery and aviary type systems as a result of them falling from, or banging into perches. Research at Heriot-Watt University and the Roslin Institute has used video cameras to understand birds’ behaviour in perchery systems as a basis for designing safer housing. Birds kept in loose-house conditions can suffer significantly from feather pecking.

Hens in large groups often fail to make full use of the available space. Scientists at Roslin Institute found that behaviour appeared to be influenced by flock size. For example, birds in large groups with access to the outside still remain inside; only about 10-20% of the birds go out at one time. In contrast, small flocks will go outside. It is possible that in the larger flocks it is the stress of having to pass a high proportion of social strangers that keeps birds inside.

Commercial flocks are unnatural: instead of one cockerel and a dozen or so hens, commercial flocks contain several thousands of hens. As battery cages are phased-out, selection of optimum flock sizes and appropriate housing design will become increasingly important welfare issues.

Eggshell quality could be a good and noninvasive way of detecting stress in laying hens. Researchers at the University of Glasgow are exploring how shell quality might be used to identify "hidden" factors in poultry housing and handling that cause stress.

Scientists at Roslin Institute found that caged hens made full use of nesting materials provided to them, suggesting that this enabled them to carry out an important natural behaviour.

However, this may not be as simple as it sounds and there may be important implications for cage design. Providing nest sites in conventional cages might increase stress because birds may need to have their nest site in a separate area. The research showed that nest-building behaviour is not eliminated by providing birds with pre-formed nests. This may have important welfare implications because its suggests that birds might need space to perform this behaviour even if a nest is provided.


Adequate stimulation may be an important determinant of mental well being in animals. For example, foraging and exploratory pecking appear to provide important stimulation for chickens. Barren and unchanging environments in poultry houses are associated with increased fearfulness, depression, feather pecking and even cognitive impairment. There are good reasons, therefore, for assuming that environmental enrichment, through the provision of appropriate novel objects, can benefit poultry welfare.

Care is needed, however, in identifying effective enrichment. For example, novel objects are potentially frightening to animals, so an individual’s apparent interest in an object may reflect its need to overcome fear, rather than a positive response. Some alleged enrichment devices for hens have been shown to elicit alarm and to increase feather pecking.

Rather than testing enrichment methods on a "trial and error" basis, using human perceptions of what animals might prefer, scientists are trying to understand how animals perceive different objects and what they find stimulating.

At Roslin Institute researchers found that pieces of string are a particularly attractive pecking stimulus for chicks and adult hens. They systematically offered the birds a variety of materials including beads, chains, baubles, feathers and bunches of string, and recorded their interest. The birds showed clear and specific pecking preferences. White string was the most stimulating. Yellow string also elicited a strong response. Red, green and blue strings were much less effective. Monochromatic devices were more attractive than multi-coloured ones, and static ones were pecked more than those that were moved occasionally. Providing chickens with string devices reduced feather pecking and improved plumage condition in the laboratory and at commercial farms.

There have been reports that music may have a calming effect on poultry. Scientists at Roslin Institute conducted a survey among farmers. Over one hundred farmers were asked whether they played music to their flocks and whether they noticed any benefits. 46% routinely played music to their birds. Of these 96% said it calmed the chickens, 52% felt the birds were less aggressive, 20% reported healthier birds and 16% claimed increased egg production. Of those farmers who did not play music 90% said they would consider it. Playing the radio to hens may prove to be an easy and practical way of enriching their environment and perhaps of helping to reduce their fear of new noises. However, this is an area that has received little empirical scientific investigation.

Many commercially reared poultry are housed in environments in which their vision is restricted, for example, by low levels of lighting. Researchers at Roslin Institute showed that chicks and adult hens are readily attracted to abstract video images that are presented outside their cages. So, enrichment of the environment around cages could contribute to improved welfare for poultry.

Smells, particularly those associated with predators, help to trigger a fear response in hens. Researchers at Roslin Institute and the University of Sussex reviewed evidence that hens' sense of smell is important in their attachment to familiar objects, valuable resources, and their general environment, in a similar way to the odour cues used by rodents. The presence of a familiar smell reduced chicks' fear of an unfamiliar environment and of strange birds; it also accelerated their acceptance of a food they had never experienced before. So, it is likely that incorporating a familiar odourant into a novel situation could reduce fear and anxiety in poultry - a sort of aromatherapy for birds. Such sensory enrichment might be especially beneficial in the rearing of young birds, by acclimatising them to smells that they will encounter later in life.


Lighting in poultry houses strongly affects birds’ behaviour and so impacts on their welfare. Lighting levels are usually set according to human perception, but recent research at Silsoe Research Institute shows that poultry perceive the brightness of light sources differently from humans. It is now clear that lighting specifications that are optimal for humans are, in many cases, not suitable for poultry.

It might be that birds prefer to perform different behaviours at different light levels. The Silsoe studies show that 2- week old hens prefer higher light levels than 6- week old hens. The older birds prefer lower levels of light for resting and perching which accounts for 60% of their time, and higher levels for all other activities.

Lighting levels are probably important in enabling birds to recognise each other, and this recognition may reduce aggression and affect feeding behaviour and mate choice. Good lighting is also important in enabling birds to jump accurately between perches and so avoid injury. Researchers at Heriot Watt University and the Roslin Institute are investigating how the level and type of illumination in aviary and perchery poultry houses affect birds' ability to jump between perches. They are also investigating the effects of visual contrast of the perches, and of obstruction of perches and how birds may be distracted by other perching hens.

Scientists at Silsoe Research Institute measured the vision of broiler chickens at different wavelengths using a behavioural test. Chickens were trained to peck one of two panels for a food reward. The panels were lit with filtered light at different wavelengths. The birds were also sensitive to UV wavelengths, implying that chicken see colour differently from humans.

Scientists at Silsoe Research Institute have developed a new apparatus for measuring light in poultry houses. The CLUX meter provides estimates of how chickens perceive the brightness, and makes measurement of the light sources. The researchers plan to combine the use of the CLUX meter with their knowledge of poultry responses to provide producers with strategies for overcoming production or behavioural problems. The apparatus can be used in growing houses for chickens, turkeys and ducks.


Animals tend to find novel experiences frightening and stressful. So, infrequent contact with humans, movement into new surroundings and mixing with other unfamiliar animals will be stressful to varying degrees. Such activities are, however, essential features of animal management on farms and, for example, in zoos. Several lines of research are aimed at identifying and minimising key stress factors.

Research at the Roslin Institute showed that handling chickens regularly, or even just letting them see people, was helpful in reducing their fear of humans. In some cases though, animals may prefer to interact with machines rather than people. Several research groups are exploring the development of "hands off" systems of moving animals and monitoring their behaviour.

Working in collaboration with the poultry industry, and with funding from the former MAFF, scientists at Silsoe Research Institute have designed improved systems for loading chickens on to transport vehicles. They have developed a wheeled module that holds around 60 birds in drawers and is small enough to be put close to the cages so that the birds can be transferred and wheeled directly onto the lorry with minimum handling. A major egg producer is testing the system.

The RSPCA has funded further research to find a module system to improve turkey welfare during loading.

Scientists at Silsoe Research Institute are exploring a variety of remote-sensing technologies that deploy computers and mathematical modelling to monitor animal performance without the need for handling. A new system called Growth Rate and Conformation Evaluation (GRACE) uses image analysis techniques to monitor the weight, growth and condition of pigs without manual handling. A video camera mounted over the feeder, collects images of pigs as they enter. Each pig is identified by its electronic tag. The images are analysed to measure body area, ham width, and ham area. GRACE will allow farmers to spend more time looking after the health and welfare of their stock and it will alert them to any changes in condition and behaviour, for example, if one pig is not feeding. This could help in identifying health problems that might otherwise go unnoticed. GRACE is being taken up commercially by Hunday Electronics to bring this technology to the market place.

Biosensors are being developed for a range of automated, non-invasive ways of monitoring animal health as part of integrated management systems. For example, research at Silsoe has led to a prototype sensor for predicting ovulation and pregnancy in cattle, which is based on sensitive analysis of levels of the hormone progesterone in milk. Scientists at the Universities of Glasgow and Stirling have explored low-stress ways for fish farmers to grade salmon without having to handle them. This has involved exploiting natural behavioural differences in fish to move them between cages, and video imaging techniques to predict body mass and maturation.

Researchers at Silsoe have developed a remote sensing system for monitoring the health and fertility of dairy cows. In collaboration with Fullwood Ltd, they have adapted a feeder system so that feed is dispensed to a cow only after she had blown breath into an inlet above the trough. The breath is drawn into bags where an infra-red analyser detects detect the presence of gases that indicate the animal's health. Cows learn to use the feeder in just a few visits.

The same research group is developing a system for monitoring poultry. In this, birds are weighed automatically by electronic perches. From the recorded data, a computer model provides information about the composition and quantity of feed required to meet the birds' requirements.

Several research projects are aimed at improving pre-slaughter handling and welfare of animals. An example is research from Roslin Institute, which found that covering broilers heads with an opaque hood, and lowering light intensity could reduce wing flapping and struggling when the birds are shackled prior to slaughter.


The transport of animals to and from markets, to slaughter and particularly on export journeys, raises several welfare concerns:

  • fear and pain associated with handling and mixing
  • thermal or motion stresses during the journey
  • thirst and exhaustion
  • risks of infection

A central theme of research into improving animal transportation is to identify the animals' physiological and mental well-being needs, and to devise procedures that meet them. Pigs are particularly susceptible to stress during transport. Scientists at Cambridge University and Silsoe Research Institute have studied the effects of vehicle motion on pigs. They found that during both simulated and actual journeys the pigs showed signs of travel sickness. This research has resulted in new recommendations for the way pigs should be transported.

There are also welfare problems associated with the transportation of chickens, the worst of these being heat or cold stress, cramped conditions and the pain associated with motion of the vehicle on injured legs.

Researchers at Silsoe Research Institute and the University of Bristol, with funding support from industry, the Humane Slaughter Association and the former MAFF, have addressed the welfare implications of different methods currently used to kill trout. They assessed welfare both subjectively and by examination of behaviour, indicators of sensibility and indicators of brain stem reflexes. This suggested that the highest welfare standards and the lowest operating costs were likely to be achieved by electrically stunning the fish as they flow through a pipe. For humane killing, it is necessary for the electrical stun to render the fish instantaneously insensible and to ensure that it does not recover from insensibility before death occurs from lack of oxygen. The research has defined stunning parameters that meet these criteria.

Scientists at Roslin Institute and Silsoe Research Institute, together with a major broiler producer and with funding from the former MAFF, designed a new transport vehicle aimed at improving the welfare of chickens during transportation. The fan ventilated vehicle named "Concept 2000" was launched in May 1999. It has been shown to reduce mortality substantially during journeys and to improve both animal welfare and product quality and value by reducing transport stress.

The new vehicle was designed using data from experiments in which the scientists monitored temperature and humidity of chicken transport vehicles during routine journeys. They found that there was a "thermal core" of higher temperature and humidity, irrespective of the season or whether the curtains were up or down. The scientists also determined physiological indicators of stress in birds, such as deep body temperatures and panting. This enabled them to define combinations of temperature and humidity that are acceptable for birds in transit.

It was shown that the environment could be improved by controlled forced ventilation of the vehicle and hence the fan-assisted design of Concept 2000 was achieved. The trailer has its own generator to provide independence from the tractor unit and sensors to warn the driver if conditions in the vehicle approach critical limits.

Concept 2000 promises to be the design of choice when broiler producers replace existing broiler transporters over the next few years.

The researchers are conducting similar work with other farm animal species.

Source: The Biotechnology and Biological Sciences Research Council - Summer 2002

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