Welfare and Health
Good health is arguably one of the principal, if not the principal element, of animal welfare. In some instance, particularly with intensively reared livestock, conditions of handling and management that affect welfare are also intimately related to poor health.
Respiratory diseases and aerial pollution
There is increasing evidence that respiratory disease in intensively housed pigs is caused by
aerial pollutants such as dusts and ammonia. Elimination of these diseases by medication,
vaccination or by eliminating specific pathogens has proved costly and often ineffective. In future, control methods are more likely to depend on environmental and biological control methods.
Researchers at the University of Bristol, Silsoe Research Institute and Institute for Animal
Health have worked together to analyse the relationship between infectious diseases of the respiratory tract and intensively managed housing. Their aim is to provide information that will help to improve building design and management, so that the incidence and severity of respiratory diseases are reduced. In order to achieve this they looked at the causes of the diseases, how pollutants might predispose animals to infection, as well the dynamics of the generation and clearance of aerial pollutants. The Bristol team is aiming to identify hygiene tolerance levels for pollutants such as ammonia, and particles of protein dust, for maximum health, productivity and welfare.
The Silsoe team has identified key processes that can contribute to an integrated system for controlling aerial emissions in poultry houses. These are:
- dietary manipulation to reduce excretion of urea and pathogens
- cleaning of the exhaust air in mechanically ventilated buildings, possibly using a bio- filter
- drying of the manure from layer birds, both on belts and deep pits, using the ventilation system
- combustion of litter.
Lameness in cattle
Lameness in dairy cattle is a major animal welfare issue. It is almost always a painful condition and it interferes with a cow's ability to interact fully with her environment, in particular her social environment. Lameness is also an economic problem, it can cause loss of weight, eventual reduction in milk yield and reduced fertility: all of which may result in early culling. In the dairy herd, lameness is mainly due to foot problems but can also be caused by leg damage, including swollen knees and hocks caused by poor lying conditions and poorly designed housing.
Lameness is more common during calving. Scientists at the University of Bristol are looking at the reasons for this. They believe that as well as external mechanical stress, biochemical changes associated with calving and the onset of lactation compromise the connective tissue that supports the skeleton within the foot and cause the pedal bone to sink and progressively destroy the sole of the hoof from within. The biochemical mechanisms are, as yet, incompletely understood, but it
appears that these primary changes are directly linked to events around calving. The practical consequence of this is that sole lameness in dairy cows can be significantly reduced by minimising external stresses on the feet only at this critical time.
Osteoporosis in laying hens is the progressive loss of structural bone during the laying period. It causes the bones to become fragile and easily fractured, for example when the birds are removed from their cages. It is estimated that bone fractures occur in about 25% of laying hens and it therefore
constitutes a serious welfare problem.
Some nutritional approaches such as supplying a particulate source of calcium can be of some help, but research at Roslin Institute has shown that whereas poor nutrition can make the osteoporosis worse, good nutrition cannot prevent it. Roslin scientists have used image analysis of bone structure, radiographic data about mineral density and direct measurement of bone strength in post mortem samples from layers, to develop a "bone index" for the strength of bones in individual birds. This can be used in breeding studies with the hens' offspring to select for birds with enhanced bone
strength and greater resistance to osteoporosis. Such selection could form the basis of improved commercial breeding programmes.
Providing maternal care for orphan or triplet lambs
Farmers use a variety of approaches to rear orphan lambs or the third of a set of triplets that cannot be fed effectively by its mother. These range from persuading a ewe that has just given birth to adopt them alongside her own lamb to dispensing with maternal care altogether and rearing the lambs on milk-bars. Unfortunately, most techniques for using ewes as foster mothers are impractical on a large scale, labour intensive and have a poor success rate. Rearing on milk-bars is also an expensive option and normal behavioural development of lambs may be compromised due to absence of
important maternal education.
Scientists at Babraham Institute and University of Cambridge have studied the physiological events that control induction of lactation, maternal behaviour and bonding between a ewe and her lamb. This research has led to two protocols for providing maternal care for orphan and triplet lambs:
Ewes that have recently given birth can be induced to act as foster mothers by simple manual palpation of the vagina and cervix for 2 minutes, even up to 3 days after they gave birth. This procedure works because it sets in motion the same chemical changes in the brain which normally induce maternal behaviour and bonding at birth.
Non-pregnant ewes can be stimulated to lactate in six weeks using intravaginal
sponges impregnated with the hormones progesterone and oestradiol. Following manual palpation of the vagina and cervix they will rear orphan and triplet lambs through to weaning with identical growth
rates to normally reared lambs.
Both techniques offer farmers a more effective and less labour intensive way of rearing the lambs and can be used to foster across breeds.
Heat stress in laying hens
Chronic heat stress, resulting from a hen's inability to regulate its body temperature at high environmental temperatures and humidities can be a problem in well insulated poultry houses during hot summer days. As well as physiologically harmful effects such as metabolic changes and hormonal imbalances and tissue damage, heat stress also alters birds' behaviour and depresses egg production
and eggshell quality.
The effects of heat stress can be alleviated both by physical procedures such as increased ventilation but also by dietary manipulation. Vitamin C is commonly added to the diets of birds under heat stress. Scientists at the Roslin Institute found that treatment with this vitamin could also reduce fearfulness in chickens and quail. Other research at the Roslin Institute showed that adding extra vitamin E is also beneficial, provided the vitamin is added before the onset of heat
stress: it is not effective if added only after the hot period has started. The findings suggest
that adding vitamin E to the birds' drinking water at the approach of hot weather could be
In this booklet we have attempted to give a flavour of current and recent research that relates to understanding and improving animal welfare. We have focused upon research funded by the BBSRC or undertaken at BBSRCsponsored institutes. Inevitably, it has not been possible to include everything. Further details, including up to date list of projects and programmes of research are accessible via the BBSRC web site (www.bbsrc.ac.uk) and the web sites of the individual institutes which can be accessed from the BBSRC site.
Many areas of basic science, for example in physiology and genetics, provide information that can contribute to overall understanding of animal biology, including behavioural and welfare issues. Research in genomics and cell biology that is aimed at developing or improving alternatives to the use of animals in some experimentation may also be said to contribute indirectly to animal welfare. Again, further information is available on the web sites.
In compiling this booklet, BBSRC gratefully acknowledges the input and help of many people: especially: Professor Richard Andrew, Dr Nicola Clayton, Dr Mike Gentle, Dr Lesley Heppell, Professor Jane Hurst, Dr Bryan Jones, Professor Keith Kendrick, Dr Georgia Mason, Dr Mike Mendl, Dr Malcolm Mitchell, Professor Christine Nicol, Professor Christopher Wathes, Professor John Webster, Professor Andrew Whiten and their colleagues.
Source: The Biotechnology and Biological Sciences Research Council - Summer 2002