«October 2009 SCIENTIFIC COORDINATOR Pierre Le Neindre, Senior research scientist, INRA (French National Institute for Agricultural Research) ...»
4.3.3. Castration This is an age-old practice in all species and is found in all systems of rearing whether intensive, organic or qualitylabelled. It is done for reasons that are connected with the quality of the meat or the behaviour of the animals.
Piglets The major motivation for castrating piglets is to improve the quality of the meat of male pigs by eliminating male odours in the carcass brought on by sexual hormones. In addition, it makes rearing easier by reducing the amount of aggressive and sexual behaviour of the animals and hence the amount of wounding. In Europe 80% of pigs are castrated by surgical means. In France, as in most other European countries, castration is performed by surgery without anaesthesia or analgesic treatment (see Chapter 5 for the cultural, regulatory and economic constraints that explain in part this situation). Behavioural observations and physiological studies show that this practice is a source of acute pain as the tissues involved are innervated. During castration most piglets scream loudly and at a frequency that is characteristic of painful situations. Just after the castration the HPA axis and the sympathetic nervous system are activated but this activation disappears by the next day. The behaviour of the animals also changes following castration. This happens in the first hours after the operation and is marked by a reduction in movement, isolation, prostration, less time at the udder of the sow, stretching of the hind legs, trembling and spasms. Some of these disturbances continue for several days after the operation, for example, huddling up, showing less synchrony of activities with litter mates, scratching the incision in the rump and tail wagging. Finally, there does not seem to be any clear effect of the age at castration on the outcome in terms of the pain caused by the procedure. Even though healing is better when the piglets are castrated very young, it seems that they have a slower growth rate due to being disadvantaged in the competition for teats which results in their use of the less productive ones.
In summary, castration is a practice that has positive effects in the long term on potential sources of pain in intensive piggeries by limiting aggressive behaviour and thus lesions, wounds, lameness and fractures. However the information in the literature clearly shows that pain is acute during castration, then strong for several hours afterwards, followed by more moderate pain for several days following castration.
Cattle and sheep Castration of cattle and sheep results principally in a reduction in the level of testosterone. There are a range of reasons for castrating. The first is to allow joint rearing of young females and castrated males (heifers and steers for cattle) on the same pastures in grazing systems. Secondly, it reduces between-animal aggressiveness and sexual activity and improves the docility of the animals. It also results in greater marbling of the meat (increased intramuscular fat), a quality appreciated by the consumer, but leads to a slower rate of growth than in entire males.
There are three major methods of castration of calves; crushing of the testicular cord, usually by the Burdizzo clamp, constriction, usually using rubber rings and surgical removal.
Studies into castration of cattle show that it is a source of acute and chronic pain. This is the case regardless of the technique used and/or the age of the animal being castrated. However there are some differences in intensity according to the technique and age. Increases in cortisol levels and the incidence of abnormal behaviours and postures are manifestations of this effect. The existence of chronic pain is inferred from specific behaviours associated with the site of castration and abnormal posture. It seems that the intensity of the pain at the time of castration with the Burdizzo clamp is less strong than with surgical castration, although the Burdizzo is rarely used in France because of its cost, its danger to the operator and the possible failures of the technique. Surgery is the 64 Expertise scientifique collective "Douleurs animales" technique that causes the briefest pain. It is as dangerous for the operators as the Burdizzo but is much less onerous. There are no failures or setbacks except for possible post-operative problems. The rubber ring is the means of castration most used by breeders, except in the United Kingdom. It induces chronic pain that is more difficult to detect and to manage than that observed following castration by other methods. Finally, the intensity of the pain is proportional to the age of the animal. Only a minority of breeders use anaesthetics to castrate their calves except in Switzerland where its use is mandatory. In contrast most veterinary surgeons use anaesthetics for castration (see Chapter 5). In sheep, the situation is similar: The Burdizzo method is recognised as being the least painful while the rubber ring method is the most practical for its ease of use. However the practice is not common in France.
In summary, it is evident from the literature that castration of calves should be practised:
• as early as possible; preferably by one week of age and not later than 45 days of age,
• by using the Burdizzo clamp method,
• using an analgesic protocol associating administration of NSAIDs 20 minutes before the operation with a local anaesthetic by infiltrating 2% lidocaine (about 5 ml) into the distal scrotum. Adding the use of an alpha 2 agonist at or around the time of the operation is also worth considering.
Poultry Castration of poultry, or caponisation, is mainly practised in chickens and more occasionally in guinea fowl. It has a double purpose: (1) to avoid pecking and the significant mortality that can result and (2) to obtain marbled meat of the desired gustatory quality. Caponising consists of removing the testes, which are internal, by way of one or two lateral incisions, most often on conscious animals without anaesthesia or analgesia. Typical behavioural indicators such as vocalisation and raised blood concentrations of corticosterone indicate a high level of stress from the time of capture and restraint onwards then strong reactions during the surgical act. Combined use of a tranquiliser and an anaesthetic has been proposed. General anaesthetics are difficult to use in poultry because there is a wide variation in the duration of effect of the anaesthetic and the first animals to wake up must be immediately separated from their mates to avoid cannibalism and post-surgical complications resulting from them soiling the wounds of their still-anaesthetised companions (see also Chapter 5).
4.3.4. Non-use of pain relief for mutilations Even though the mutilations described previously often have many justifications, such as health, decreased risk of wounding and husbandry benefits, it does not make them any less painful and this is exacerbated by the fact that the pain produced is not treated pharmacologically. In Chapter 5 we highlight more explicitly the therapeutic possibilities, but we can note at this point that very few studies are available on ways of implementing the interventions that we have described. We must also emphasise the legal impossibility of having access to certain substances either for use by the breeder (for example local anaesthetics) or for their utilisation in commercial animals (cf Chapter 5). Finally, for some species of fish and poultry there existing chemicals that can be used and the scientific questions about the reality of pain in these species remain unanswered. (cf Chapter 2) We have available some information that comes from surveys of breeders and veterinary surgeons working in the pig and cattle industries in France and several other countries in Europe (see Chapter 5). For castration in pigs, there is no treatment for pain presently in use in France. In cattle, the practices used by veterinary surgeons in France and the rest of Europe seem similar except for some specific situations like the dehorning of calves, for which the differences can be explained by the legislation in place in the various countries. The main differences for the other mutilations relate not to the use of local anaesthetic, which is used practically universally, but rather to the use of complementary, post-operative treatment with NSAIDs which seem to be used more routinely in the rest of Europe (see Chapter 5) than in France. Some studies report that the cost of substances and the regulations that control their accessibility are the stumbling blocks to their use by breeders. There is general agreement however in these studies on the existence of pain in cattle and on the necessity for pain relief, as much for ethical and medical reasons as for husbandry considerations.
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4.4. Known or potential sources of pain associated with genetic selection From the 1960s onwards, animal selection became organized in breeding programmes for genetic improvement of commercial animals, looking in most cases at the economic viability of animal breeding in the broad sense. The combination of genetic selection for improving production and enhancing the conditions of animal husbandry may have had consequences for the metabolism, reproduction and/or the health of the animals.
4.4.1. Examples in pigs A significant source of pain concerns locomotor problems, and particularly problems of leg conformation and lameness which follows from them. This lameness is multifactorial but genetic factors are strongly implicated in the weakness of the limbs linked to problems of ossification of the cartilage (osteochondrosis).
A well-known example of the negative effect of genetic selection in the pig is a muscular problem, PSE, which develops as a result of an acute stress or exposure to halothane anaesthetic (see Chapter 5) and is characterised by rapid death of the animalCertain breeds of pig, particularly the Piétrain, have a high frequency of this syndrome as well as a general muscular fragility. Animals of this genotype often have locomotor problems when being moved (mortality, inability to move, cardio-respiratory trouble) and this is probably associated with pain. However, the Piétrain is only maintained as a pure breed by specialised studs and artificial insemination centres because it is used exclusively as a terminal sire. The relevant genes are recessive, so pigs destined for the abattoirs who carry them are unaffected by the syndrome and do not pass on the anomaly.
Certain behavioural disorders that are multifactorial in their aetiology and are partly heritable, seem to be more frequent in genotypes selected for lean carcasses. A case in point is aggressiveness which is a potential source of social stress and tissue damage due to biting. Similarly, it seems that there is a genetic element to tail biting, with probably a higher risk in genotypes selected for very lean carcasses. A particularly undesirable form of aggression is the behaviour of the sow towards her newborn litter.
Yet another adverse effect of genetics concerns the selection of sows for higher prolificacy which is accompanied by an increase in the mortality of the piglets. In addition, with certain very prolific sows, the number of piglets exceeds the number of teats which forces breeders to carry out cross fostering of piglets or to wean them at a very early age.
4.4.2. Examples in poultry Selection of poultry for production traits has had significant impact on the appearance of situations involving pain.
Furthermore, the very practice of genetic selection involves measuring the characteristics of the animals intended for selection on an individual basis, and so they have to be reared in individual cages. This type of accommodation can lead to an increase of the prevalence of foot problems, leg conformation and dermatitis of the foot in meat birds.
The most common selection criteria are: for meat birds (1) selection for growth, which results in an increase in sexual dimorphism in certain species and improvement in the food conversion index, two characters that are genetically linked; (2) selection for increased mass of pectoral muscles which constitute the most "noble" meat of the carcass, which leads indirectly to joint problems in the lower limbs in certain genotypes due to the forward displacement of the centre of gravity of the animal; and for laying hens (3) selection for the number of eggs produced, and therefore intense phospho-calcium metabolism which increases the risk of mineral deficiency and with it an increased risk of fractures by the end of the laying life because the skeleton becomes more and more osteoporotic as the animal gets older.
66 Expertise scientifique collective "Douleurs animales" In addition, in certain species genetic selection has been accompanied by behavioural responses that can cause injuries or panic likely to cause suffocation, for instance in the mule duck which has well-established escape reactions when facing humans.
Of course, these potentially-stressful indirect consequences of the selection process should be weighed against the benefits of the possible prevention of much pain by introducing characters which are associated with pain prevention into selection schemes (cf. Chapter 5).
4.4.3. Examples in cattle Several sources of pain potentially linked to the genetic selection of cattle are described in the literature.
Undesirable genetic correlations have been shown between milk production and parameters associated with metabolism and health. The health of the highest producers of milk in dairy breeds seems more fragile than that of the others. In addition, susceptibility to mastitis, respiratory diseases and calving difficulties as well as risks of digestive disorders, lameness or wounds of the limbs and joints are implicated in several studies as genetic factors indirectly linked to selection for criteria that relate to the capacity to produce milk.
In beef cattle, calving difficulties are frequently seen, especially in certain breeds and in young animals, such as those calving at two years of age. An example is that of the muscular hypertrophy linked to the presence of the double muscle gene (culard gene) which can cause problems in the limbs and, above all, difficult calving, which leads directly to an increase in the number of Caesarean sections. The procedure is potentially painful if practised without anaesthetic which raises questions about the repetition of Caesareans necessary to extract calves of the Belgian Blue breed of cattle (see Chapter 5).