Comportamento de suínos

Agressividade e brigas em suínos

In natural settings, aggression between pigs is rarely observed beyond the first week of life, when piglets establish the teat order. In intensive rearing systems, however, aggression between pigs is common.

Aggression caused by mixing unfamiliar individuals is a major welfare concern during intensive production of growing pigs and sows.

• Mixing is frequent after weaning, when the piglets are separated from the sow. During growing and finishing stages, pigs can be regrouped multiple times to meet spacing and feed requirements.

• Intensive production systems usually isolate gilts and sows during both gestation and reproduction; nonetheless, aggression has been recorded between individuals in neighboring crates.

• Group sow housing has become more common in swine production. Although group housing of sows has many benefits for sow welfare, aggression between sows is frequently observed when new individuals are introduced to the group pen. Under more extensive management, regrouping based on reproductive stage is also common.

• Mixing during transportation and at slaughter is also very common.

In growing pigs, producers often form homogeneous groups of individuals with similar weights; however, this practice slows the establishment of a new social order. Because pigs have similar competitive abilities, fights last longer. After losing a fight, pigs are also more likely to retaliate, resulting in an overall increase in the number of aggressive behaviors.

Fights usually adhere to the following behavior sequence: 1–2 minutes of nosing and sniffing each other, often while vocalizing, until the fight breaks out into biting and shoving. Fights generally end when one of the pigs retreats or displays submission to the other.

Over time, fights are gradually replaced by threats, avoidance, and withdrawal behaviors until the hierarchy is formed, usually within a few days after the introduction of new animals.

Limited space at the feed trough or limited amounts of concentrated feed can cause aggression even in stable social groups. When females are in estrus, boars might fight and become very vocal; boars will strut shoulder to shoulder, champ their jaws (producing pheromone-rich saliva), and then finally face each other and attack. Serious injuries can result, especially among boars that still have their tusks.

Under intensive management, boars are generally housed individually, away from sows and other males; therefore, instances of fighting are highly unlikely. Breed and genetics play a role in the prevalence of aggression in pigs: Large Whites tend to be more aggressive than Hampshires, which tend to be more aggressive than Durocs. Leaner breeds tend to be more aggressive when handled than are those with more body fat.

Skin lesions result from biting during fights between pigs. Injuries sustained from fighting have an immediate negative impact on the welfare of pigs. Aggression can also hinder weight gain and affect reproductive performance.

During estrus, sows might show severe aggression toward newly introduced individuals. Research has found that submissive sows show the least estrous behavior, have smaller litters, and eventually lose body condition, because they are less successful in gaining access to feed in competitive systems (eg, floor feeding, nongated stalls). Injuries and stress related to aggression can decrease meat quality and require cuttings on the carcass.

The primary way to decrease aggression is to keep pigs in stable social groups. When mixing is unavoidable, aggression is most efficiently decreased using a combination of multiple approaches. Early-life socialization by allowing multiple litters to interact as they would under natural conditions can help decrease aggression at weaning.

Aggression can be decreased by providing adequate space for the display of avoidance and retreat behaviors, by including shelters or dividers in the pen, and by mixing subgroups with preestablished relationships. Progressive introduction of existing groups by first housing them in adjacent pens can also decrease aggression. Maternal or boar pheromones, as well as mixing at sunset or dimming the lights, have also been used successfully to decrease aggression.

Feeding diets high in tryptophan (a precursor for serotonin) or administering tranquilizing drugs (eg, azaperone or amperozide) can mitigate aggression and stress. Electronic sow feeders where individuals enter a stall to receive their feed can help decrease aggression due to competition for feed.

Mordedura da cauda em suínos

Tail biting in pigs, which involves one pig biting or chewing on the tail of another pig and causing open wounds, occurs mostly in confined environments.

Boredom, competition for food, and the inability to perform species-specific oral behaviors all drive tail biting in pigs. Tail biting can be a direct aggressive behavior or begin as gentle manipulation before escalating. Once the behavior appears in a pen, if the first few biting pigs are not removed promptly, it spreads rapidly.

It has been suggested that tail biting spreads through a pen as a result of social facilitation or stimulus enhancement (in which the bitten tail stimulates further investigation, resulting in an increase in the behavior’s prevalence). Tail-biting injuries are likely to become infected and result in culling; cuttings in the carcass also might be required.

The most efficient way to decrease tail biting is to provide opportunities to express natural rooting and nosing behaviors. Providing more space and a rooting substrate, such as light clean straw, has been successful in preventing outbreaks.

Feed type and delivery have also been found to affect tail biting: floor-feeding of pellets, compared with trough-feeding of liquid meals, increases the risk of tail biting. Environmental enrichments such as rubber toys or metal chains are efficient as a short-term solution because they are novel; however, pigs’ interest wears off over time.

Tail docking, though commonly used to address tail-biting behavior, focuses on the sign rather than on the underlying causes. Biting behavior might then be redirected toward the ears or the vulva.

Comportamento sexual e materno de suínos

Comportamentos estereotipados dos suínos

Stereotypical behaviors (stereotypies) are repetitive actions with no apparent purpose. They are often observed when the environment does not provide for the animal’s needs and reflects a state of poor welfare. Opportunities to express species-specific behaviors must be provided to decrease the incidence of stereotypies.

In juvenile pigs, the most common stereotypy is belly nosing, a behavior that stems from a strong suckling motivation, because weaning occurs much earlier in intensive production systems than under natural conditions.

Belly nosing is characterized by repeated movements of the snout on the belly of another piglet. This behavior can be mitigated by providing outdoor housing or providing bedding such as straw in indoor environments.

Ear biting or tail biting of a social partner (see Tail Biting in Pigs), if done repetitively and obsessively, constitutes a stereotypy. Ropes and balls in the environment temporarily lower the frequency of these behaviors. However, the initial novelty of these enrichments quickly wears off, thus decreasing their effectiveness, even when they are rotated regularly between multiple items.

Nonnutritive oral stereotypies are frequently observed in sows. Examples include the following:

• bar biting (chewing on the bars of the pen)

• head waving (side-to-side tilting movement of the head)

• sham or vacuum chewing (chewing motions performed without food or substrate)

• tongue rolling (extension and curling of the tongue outside the mouth)

• rubbing the snout against a barren surface

• polydipsia (ingesting high amounts of water)

In sows, these oral stereotypies are attributed to severe restriction of the animals' movement in conventional systems. The behaviors are much less frequent in loose housing systems.

Sows are generally fed highly concentrated diets once per day, often presented as pellets, that satisfy their nutritional requirements. However, such feeding schedules do not provide the opportunity for foraging behaviors such as rooting and grazing, which pigs would spend up to 10 hours a day performing under natural conditions. Providing sows with a high-fiber diet can increase the time they spend eating and thus decrease oral stereotypies.