1. Immune and production indicators of animal welfare
Module 5
Immune and production indicators of animal welfare

2. Learning objectives
To understand the relationship between welfare and disease
To understand the relationship between welfare and production performance
To assess the levels of disease and production

3. Summary of content Effect of disease on welfare
Effect of welfare on disease
Effect of welfare on production
Quantification of disease and production

4. Disease and Five Freedoms
Freedom from hunger and thirst
Freedom from discomfort
Freedom from pain, injury and disease
Freedom to express normal behaviour
Freedom from fear and distress
A disease may affect many different aspects of welfare. It may affect all of the Five Freedoms.
For example, an animal with a chronic skin abscess may not be able to compete with other animals for food and water. The abscess may prevent the animal from laying in a comfortable position, and it may not be able to compete with others for a warm laying area. The abscess will cause pain. Normal behaviour will be affected as the animal will attempt to avoid further injury, and it will be generally dull and inactive. Animals that are ill can often be more fearful of other animals as they are more prone to predators.
It is important to recognise that both prevention of the disease and treatment are important.
For prevention this may include vaccination programmes or improvements in husbandry systems.
Treatment includes both proper diagnosis and treatment. A delay in treatment increases the welfare consequences of the disease.

5. Disease and pain
Pain is probably the most important consequence of disease
However, pain may persist for longer than the clinical signs
Sensitisation of the Central Nervous System by an acute disease may persist for several months
Disease is often closely related to pain.
It is important to remember that disease may induce pain for a longer period than the persistence of the original signs.

6. Pain may persist for months5
Threshold stimulus (N)
2.5
This study examined the increased central nervous system sensitivity following lameness in sheep (also presented in module 2).
The ‘threshold stimulus’ is the force applied to a blunt pin placed on the leg of a sheep that causes the sheep to lift its leg.
A normal sheep will respond at a force of about 5 N. However, a lame sheep will be sensitised to this stimulus and will respond at a lower pressure. This increased pain sensitivity is still present three months later despite effective treatment of the lameness.
Hence sheep after lameness will be more susceptible to painful incidents even after the lameness has been cured.
Normal
(Not lame)
Lame
Lame
(at 3 months)
(Ley et al.1995)

7. Disease and Welfare Poor welfare Disease Disease Poor welfare
Disease is closely related to welfare. A diseased animal can have many of its Five Freedoms affected. As we see from the diagram above, disease can cause poor welfare, which in turn can contribute to disease, in a vicious cycle.
Also, an animal that has poor welfare due to a separate stressor such as chronic exhaustion is more prone to disease, as the immune system is suppressed.
Poor welfare

8. Poor welfare causes disease
This graph is a diagrammatic representation of the body’s response to a persistent stressor.
The body’s initial response (red) is extreme. However, this stabilises into a steady state (green). If the stressor persists for long enough the energy required to maintain this response will lead to exhaustion (yellow) which may result in disease or death.

9. Example 1: Long term discomfort may cause disease
Depriving access to a comfortable laying area may have more significant welfare implications than simply limiting an animal’s choices
Long term discomfort may cause limb lesions (e.g. pig bursitis) or lameness (e.g. dairy cattle)
Providing a comfortable laying area is not essential for an animal’s short term survival and may be considered a luxury/unnecessary item.
However, long term deprivation of a comfortable laying area may cause diseases.
The following slides will discuss the effect of discomfort on pig bursitis and lameness in dairy cattle.

10. Bursitis on limb of finishing pig
This is a picture of a swelling around the hock region of a pig. This is termed bursitis.

11. Prevalence of bursitis is related to the comfort of the laying surface
Housing conditions
Prevalence of
lesions (%)
Deep straw + solid floor 42
Sparse straw + solid floor 44
Partially slatted 52
No straw + solid floor 54
Total slatted 84
This study assessed the prevalence of bursitis lesions as related to the comfort of the laying area.
The most comfortable conditions (deep straw) caused the fewest bursitis lesions (42%).
If straw is not been provided, the levels of bursitis lesions increase dramatically, culminating in 84% prevalence on totally slatted floors.
In other words, there is a relationship between long term comfort and disease levels.
MOUTTOTOU, N., HATCHELL, F.M. & GREEN, L.E., 1998: Adventitious bursitis of the hock in finishing pigs: prevalence, distribution and association with floor type and foot lesions. Veterinary Record 142,

12. Floor surface and desire to lie down
100 80 60
% time
spent laying 40 20
As we have seen before (module 2), a similar situation occurs in cattle.
This study assessed the time that cows spent laying in a 24 hour period on different laying surfaces in a cubicle shed. Cows provided with a soft compressible bed would lie down for about 70% of the time, which is similar to a cow grazing at pasture. However, this was reduced by a harder rubber mat or concrete.
These harder surfaces, therefore, restrict normal behaviour. Furthermore, this restriction of laying behaviour has health implications, as increased lameness is associated with reduced laying times.
Soft
Rubber
Concrete
mat
mat

13. Floor surface

14. Example 2: Transport stress plus orf infection
Transport includes several stressors
Diseases may spread quickly
The animal’s ability to combat disease is reduced
The following example relates to spread of the orf virus during transport
Transport includes several stressors such as fear, physical exhaustion, hunger and thirst.
Diseases may spread quickly because of close proximity between animals.
A combination of these stressors may reduce the ability of an animal to combat disease.
Chronic stimulation of the Hypothalamic-Pituitary-Adrenal Axis (HPA) leads to increased cortisol and suppression of the immune response (Further details of the HPA axis and its actions are available in module 4: Physiological Measures of Welfare – Part 2).
Orf is a virus that causes skin lesions around the mouths of lambs and the udders of ewes. Large proportions of flock are often affected but it usually cures itself and does not normally kill sheep.
Orf is therefore normally a relatively mild infection that most sheep can cope with - i.e. self cure. However, this may not be the case when exposed to another stressor such as transport.

15. Stress due to transport can cause disease
550 lambs were transported between Southern England and Scotland. The journey time was 23 hours due to a breakdown of the lorry (the journey would normally take six hours).
Three days after the journey, there was a severe orf outbreak in the lambs and 55 lambs died.
The lambs’ immune response was reduced because of the transport stress and this led to an increase in the symptoms and worsening of the outcome of the disease.

16. Poor welfare also reduces production
Body
Response
As we have seen before, the body is unable to maintain a response to a severe persistent stressor. In addition to making the animal more prone to disease, this exhaustion process will reduce the energy available for production - i.e. it will reduce growth rates, milk yield or fertility rate.
In the following examples we will see the effect on growth rate of two fear stressors in pigs. These stressors are:
Mixing unfamiliar pigs
Negative interaction with people.
Time

17. Example 1 : Mixing Pigs
Mixing unfamiliar pigs often results in fighting and skin injuries
Persistent fighting is a stressor that will also reduce production performance
Pigs are social animals. However, if unfamiliar pigs are mixed in a small pen then they will often fight, especially if one pig is more aggressive than the other. This is because they will not have established a dominance hierarchy (a system of social ranking based upon the relative dominance of the animals within a social group). This hierarchy needs to be developed over a period of time, and cannot occur when pigs are not familiar with each other.
The picture above shows the skin lesions that are visible at the time of slaughter if pigs are mixed during transport.

18. Persistent fear and anxiety: stress4 3 2 1
“STRESS”
Plasma
cortisol
nmol/l
In this study pregnant sows with a high rank (i.e. those that tended to be higher in the social hierarchy) were mixed with those that tended to be lower.
Those less dominant pigs (red bars) had a higher level of plasma cortisol - i.e. they were more stressed as they were the “victims” of the fighting.
Low
Rank
High
Rank
Mendl et al, 1992

19. Persistent fear and anxiety: production20 15 10 5
Total weight of piglets
(kg)
If this fighting persists then this has an influence on production.
In the study demonstrated on this slide and the previous one the sows were pregnant. This means that the energy available for the litter would have been reduced in the lower ranked/less aggressive sows (red bar).
This fighting therefore resulted in reduced production - the total weight of piglets was lower.
Low
Rank
High
Rank
Mendl et al, 1992

20. Example 2: Negative interactions with people
Negative tactile interactions (slaps or brief shocks with electrical prodders) for seconds daily
Pigs are less willing to approach stationary humans
Interactions with stockmen can also be a source of persistent fear and anxiety that can affect production.
In this example we will see the effect of slapping pigs or exposing them to brief electric shocks for 15 to 30 seconds.
The first effect is that pigs are less willing to approach the human.
This negative interaction also has implications for production.

21. Pig interaction with stockman50
100
150
Time to interact (s)
-ve
none
In this study the time taken (in seconds) for a pig to interact with a human was measured. The red bar indicates the time taken to interact for pigs that had been slapped and hit by the stockmen. The yellow bar shows the time taken for pigs to react to stockmen when they have not been subjected to either positive or negative experiences. The green bar indicates the time until interaction of pigs that were stroked in a positive manner.
The diagram above shows that those pigs that were hit (negative reactions – red bars) took much longer to come forward and interact with the stockman than those pigs which had had no interaction with stockmen (yellow bars) and those that had been stroked in a positive way (green bars).
+ve
(Gonyou et al., 1986)

22. Pig growth rate Growth rate (g/day) 800 850 900 -ve none +ve
In addition, the growth rate of finishing pigs was also measured.
Those pigs which had been hit (negative interactions – red bar) on repeated occasions grew much more slowly than those that had either no human interaction (none – yellow bar) or those that had been stroked (positive interactions – green bar).
+ve
(Gonyou et al., 1986)

23. Quantifying disease and production
On-farm observation
Medicine records
Mortality records
Production records
Abattoir findings
There are various sources of information on the disease and production status of a farm.
These relate to observation of the disease conditions on a farm. For example, a prevalence of lameness can be assessed by observing a sample of the animals walking past an observer.
The availability of records is obviously variable, but there might be records of medicine used for sick animals, or records of any deaths. There might be records of production performance such as growth and fertility rates or milk yield.
Abattoir findings may give information on chronic husbandry conditions. For example, the prevalence of old fractures in laying hens is related to husbandry conditions.

24. Quantifying human response to disease
Assessment of disease or poor production is a useful welfare indicator
However, it is also important to assess the response of the stockman to disease or poor performance
As discussed at the beginning, it is important to consider both prevention and treatment of disease - i.e. the human management of the disease.
Assessment needs to be made of the stockman’s actions in terms of prevention and treatment of disease, and steps to counteract poor production.

25. Lameness management Perceived Evaluated Acted
Does the farmer know how many lame cows he has?
Evaluated
Does the farmer know his main cause of lameness?
Acted
How quickly does he treat individuals?
Has he an action plan for improvement?
Did he get advice?
Is he following the action plan?
For example, you can assess the response of the stockman to high levels of lameness by investigating the level of perception, evaluation and action by the farmer. The above are some legitimate questions that will help to assess the stockman.

26. Perception of dairy cattle lameness30 20 % 10
The study above highlighted the difference between the number of cattle (22%) that were observed to be lame in UK dairy herds compared with the farmer’s estimate (6%) of the number of lame cows on the same day.
In other words, farmers were not aware of the level of lameness on their own farm. They are unlikely to undertake treatment or prevention if they are not even aware of the lameness levels.
Number observed
Farmer’s estimate
Whay et al, (2001)

27. Conclusions / Summary Disease can affect all Five Freedoms
Persistent exposure to stressors can cause disease and reduced production performance
Disease and production changes due to poor welfare can be assessed
Human actions (prevention and treatment) can also be assessed