Amputations

There are six types of potentially painful husbandry procedure (Table 1.12). Whether they are painful depends on how they are done, and whether an analgesic is given. The age at which they are done can also influence pain severity. Where alternative methods serve the same purpose, the more painful procedures are being discouraged. For example, research using plasma cortisol as a pain and distress indicator has shown that it is more painful to castrate lambs with a knife compared with a rubber ring. The differences between some of the alternative methods are summarized in Table 1.13.

Table 1.12. Potentially painful husbandry procedures.

Table 1.13. Relative levels of acute pain and distress following different methods used for the same amputation purpose.

Three types of pain and discomfort are present with amputation injuries. They are acute pain, inflammatory pain and neuropathic pain. Each requires a different approach when applying pain control. Acute pain and discomfort can be alleviated with a local anaesthetic or nerve block, and inflammatory pain can be treated with anti-inflammatory drugs (Mellor and Stafford, 1999). Inflammatory pain is less likely when using cauterizing methods if the heat deactivates the nerves in the wound. Neuropathic pain is more difficult to treat and can occur when there is sensitization – for example, if neuromas develop in the severed or crushed nerves. The amputation procedures that cause chronic neuropathic pain are not fully understood.

Figure 1.3 gives a schematic presentation of the plasma cortisol responses during acute and inflammatory pain with a cutting procedure. Acute pain occurs at the time the cut is made and when free nerve endings in the wound are stimulated – for example, by rubbing – whereas, inflammatory pain takes several hours to develop and is provoked by chemicals, such as bradykinin and serotonin, which accumulate at the site of the wound. If the intention is to control both types of pain, a local anaesthetic plus an anti-inflammatory drug will need to be given before the cut is made. If only a local anaesthetic is given, acute pain will be diminished, but inflammatory pain will still be present. If a long-acting local anaesthetic is given, the inflammatory pain is not eliminated, but instead it is delayed (McMeekan et al ., 1998). In some farming situations the cost of giving both a local anaesthetic and an anti-inflammatory drug would be considered prohibitive.

Fig. 1.3. Schematic curve for plasma cortisol showing the two pain components following an amputation procedure.

Easy-care systems

The following situations emphasize the need to consider the context of a farming practice when making a judgement about what is acceptable and what is unacceptable.

Many farming systems make use of compensatory growth. Compensatory growth is the acceleration in growth that occurs when a period of growth inhibition ends and favourable conditions are restored (Fig. 1.4). Growth inhibition is often due to reduced feed intake. Suppose a litter of piglets is weaned abruptly at a very early age. There is a growth check during weaning, and that check can be greater than if the litter had been weaned later on when they had already learnt to eat solid feed. However, if all goes well, the earlyweaned pigs will catch up, and during the period of compensation their growth rate is higher than normal. The final live-weight and overall growth rate of the early- and late-weaned litters can be the same, even though the early-weaned litter had a more difficult weaning period.

Fig. 1.4. Schematic growth curves for normal animals and animals that experienced a check in growth followed by compensatory growth.

In other cases, making use of compensatory growth is an appropriate thing to do, and it has good outcomes. An example where it is an acceptable practice is in broiler chickens where growth is constrained during the second week of life to improve subsequent walking ability. The reduced growth during that period is made up when the birds are returned to full feeding.

Compensatory growth is very common in subsistence livestock farming. There is seasonal underfeeding, when pasture is not growing during the dry season or during winter. The animals lose or fail to gain weight, but growth accelerates when feed becomes available again. This situation is a fact of life in subsistence farming, and discussion about its acceptability is immaterial.

Reliance on compensatory growth can, however, encourage stock keepers to be less considerate and to tolerate lack of care. Examples of this, besides early weaning, are:

● cost-saving by underfeeding during wintertime, in store and breeding animals

● failing to provide protection against inclement weather

● optimizing feed conversion efficiency in growing animals by allowing occasional periods of feed shortage or deprivation

● overstocking in order to achieve high output, leading to exaggerated seasonal underfeeding

● cost-saving on veterinary treatment and allowing non-lethal disease to take its course whilst untreated

Periods of harsh weather, poor feed quality and inadequate feed availability are inevitable, but one of the skills in livestock farming is adjusting livestock numbers according to these conditions, and knowing which type of stock needs greater feeding or care. For example, should the farmer be favouring young growing animals, replacement females or breeding adults during a temporary feed shortage?

Underfeeding may also be tolerated in the knowledge that animals make use of feed more efficiently if they are underfed. When feed intake is restricted, the efficiency of digestion increases provided feed intake is not below the animal’s maintenance requirement (Doreau et al ., 2004).

Easy-care management also has a welfare dimension at the time of parturition. Failure to assist an animal that is unable to expel a fetus because of an abnormal presentation is considered by some to be an act of negligence. Others view it as part of natural selection that is inevitable in easy-care systems, and it is for the greater good in the long term that the animal does not survive. It will not be easy to harmonize these different outlooks.