Don’t assume that the animal caregivers employed by your clients on their swine farms know enough about pig behavior to ensure the proper care of pigs.

“Increasingly, animal care givers employed on swine farms have little or no prior experience with pigs and pig behavior,” says Mike Brumm, PhD, University of Nebraska swine expert.

“Those of us who are in positions to advise producers and care givers about animal husbandry often assume a level of knowledge that may not exist. Just because we may have grown up on a pig farm and have worked with the species our entire life does not mean everyone in the industry brings the same level of experience to their daily tasks of animal care. In addition, growing up with experiences involving pigs and other livestock does not necessarily mean we fully understand the basis for the pig’s behaviors or needs.”

That’s why it is important to know from a pig’s point of view, how the pigs are reacting and adapting to their environment, says Brumm. This is especially true in today’s consolidated and increasingly integrated pork production industry where many pigs are raised in large groups using much different technologies and management systems than in the past.

Brumm focused on these issues in a seminar at this year’s American Association of Swine Veterinarians Annual Meeting in Des Moines, Iowa.

How a pig sees its world
Brumm explains that pigs have the ability to see 300 out of 360 degrees. “They can locate movement and objects in all directions except for a 60-degree arc directly to their rear. However, their ability to focus at distant objects is poor.”

That’s why they rely more on a well developed sense of smell rather than eyesight, he says, adding that researchers have shown in studies where pigs underwent bulbectomy (removal of the olfactory bulbs), the level of aggression within a pen at feeding and aggression toward strange pigs was reduced.

“In a related set of experiments, opaque contact lenses or hoods were used to obscure the vision of pigs during the establishment of social ranking following mixing. “Interference with vision had no effect on the formation of stable social groups. However, hoods, which also interfered with pheromone production from the facial area and reception of these pheromones from other pigs, prevented hierarchy rank formation in a group of eight pigs.”

Other scientists have shown in research studies that at first acquaintance, pigs frequently examine each other in the facial region, especially along the line of the jaw and around the eyes and ears, according to Brumm. “These areas may produce a specific scent or taste that is used in individual identification.”

Social ranking
Researchers also have shown that groups of 25 to 30 pigs have a relatively stable social ranking. In these groups, the dominant two to five  pigs have no need for continuous aggression since their social ranking is clear, says Brumm. The same is true of the most submissive pigs in the pen. Those pigs in the middle rank may take on another pig of middle rank in an attempt to improve status and presumed access to resources, according to Brumm.

 

The old social hierarchy model for pigs in smaller groups is not appropriate for pigs raised in larger groups.

“Weight gain in a pen is clearly related to dominance ranking,” says Brumm. “However, subordinate pigs initiate a considerable amount of aggression against dominant pigs to defend their position at the feeding trough, while pigs at the upper end of the dominance hierarchy have a prolonged eating time when at the feeder.”

Brumm says that while this is the social hierarchy model for pigs in smaller groups of  25 to 30, as pork production systems have moved to large pens of 100 or more pigs, this model is no longer appropriate.

It has been hypothesized that in large pen situations, pigs adopt a tolerant behavior versus the dominant-submissive behavior in pens of smaller groups, he explains.

“Another factor behind the differences in pig behavior between large and small pens is the ability of pigs to flee aggressive encounters,” says Brumm. “In small pens, there is limited opportunity for the losing pig in an aggressive encounter to flee the aggressor.”

Brumm points to research that has shown that “given a choice, nursery pigs that were the recipients of the most aggressive behavior used barriers when available and gained more weight when they used barriers.”

Another study showed that if there is a hiding area, piglets display normal signals of submission during an aggressive interaction, such as running away and maintaining a distance of at least three feet between themselves and the aggressor, he says.

“When two pigs are involved in an aggressive encounter, and the loser flees from the winner, the winner chases the loser no more than 20 to 25 feet in 95 percent of the encounters. Large pens allow the loser to flee far enough from the winning pig to end an aggressive encounter.

“Because large group sizes must have large pen sizes, this ability to flee from a losing encounter due to pen size is confounded with the inability to know ones social ranking in a large pen.”

Brumm points out that mixing pigs of differing sizes results in less fighting than mixing pigs of similar sizes, according to research studies. Earlier research has concluded performance can be improved when pens of dissimilar sized pigs were formed at placement than when pens of uniform sized pigs were formed, he adds.

 

Understanding how a pig eats can go a long way toward understanding possible limitations on pig growth.

There also has been some suggestion that mixing pigs later in the day versus early morning formation of social groups reduces subsequent fighting, according to Brumm.

Use of the living space
In free range conditions, pigs demonstrate several distinct behaviors, including:

  • Pigs typically appropriate or construct resting shelters in the form of mounds or burrows that may be shared by several animals. These resting sites are usually protected from wind, have partial visual cover and are well removed from feeding areas.
  • In hot weather, pigs use shady areas and wallows, with drinking places usually nearby.
  • Certain objects, such as specific rocks and tree stumps, are used as habitual rubbing posts.
  • A network of regularly used paths normally links these features and feeding locations.
  • Wild pigs adjust daily activity patterns depending partly on temperature and human disturbance.
  • Pigs depend on behavior to maintain body temperature.
  • Defecation is rare in open areas.

Knowledge of these pig behaviors and adapting facilities to them can help to ensure the best care of pigs in confinement, according to Brumm.

Since pigs prefer resting sites with protection, they generally lie in a pen with their back to a partition when possible, according to Brumm, who adds that the shape of the pen defines the amount of preferred lying area. Rectangular pens have more preferred lying areas available to the pig than square-shaped pens.

Pigs also prefer to defecate in corners, says Brumm, because this is an area of the pen where they are least likely to be disrupted.

“As the industry has evolved to large group sizes, pen sizes have also increased, but there has not been a corresponding increase in perimeter area. Pigs in large pens spend more time in portions of the pen near corners than pigs in small pens.

It has been shown that pigs prioritize their use of space in confinement facilities, according to Brumm. “The eating area is defined for them by the location of the feeder and drinker. The sleeping area is then selected based on comfort. Any area not used for these activities is eligible for dunging.”   

Understanding the pig’s eating behavior

One of the primary goals of swine housing is to provide an environment that maximizes the opportunity for pigs to grow at a rate near its genetic potential. That’s why it is important to understand how a pig eats, says University of Nebraska swine expert Mike Brumm.

“Since feed is the fuel for growth, understanding how a pig eats goes a long way towards understanding possible limitations on pig growth in swine facilities,” says Brumm. He points to these aspects of eating behavior that are important to consider:

  • As pigs grow, eating bout frequency decreases. Consequently, both the amount of feed eaten per bout and the interbout interval increases.
  • While the amount of feed eaten per bout increases, there is not a consistent increase in the length of bout. This suggests that as pigs grow, they spend a similar time at the feeder during an eating bout and the rate of ingestion of feed increases.
  • About 75 percent of daily water intake is associated with eating periods.
  • Over 33 percent of the water intake associated with eating was preprandial.
  • Research has shown that 64 percent of daily feed and 68 percent of daily water can be consumed during a 12-hour light period.
  • Approximately 75 percent of feeding activity is during daytime hours, with activity greatest from 7 a.m. to 9 a.m. and 1 p.m. to 4 p.m. There is no reported effect of age on this daytime pattern of intake.
  • Eating speed appears to be proportional to live weight. Feed intake is proportional to metabolic weight, and the rate of eating is proportional to body weight, resulting in greater total duration of eating for small pigs than for large.

Feeder design

Brumm points to a series of research trials at the Prairie Swine Center in Canada regarding eating behavior and feeder design. These trials  showed that on older feeder designs it was not uncommon to find that pigs spent in excess of 120 minutes per day eating. With newer designs, this time can be reduced considerably, allowing for a dramatic change in feeder stocking density. One conclusion from these trials is that pigs have a remarkable ability to maintain feed intake levels even though their eating behavior is curtailed by factors in their environment, according to Brumm.

Critical dimensions for pig feeders  appear to be width of the eating space, depth (feeder lip to feed access point) and lip height, says Brumm. “Small pigs begin stepping into the feeder to access feed when the depth is about 8 inches or greater, while larger pigs will not step into the feeder until the depth is about 12 inches. Width of the feeder hole should accommodate the largest pig, and the shoulder dimensions determine this width – 13 inches for a 270-pound pig. Lip height is critical for small pigs that may experience difficulty accessing feed if this is over 4 to 5 inches.

Pigs have clear preferences for eating sites and they apparently form strong preferences for one feeder hole and are often willing to wait for access to this hole versus consuming feed from an open hole, according to Brumm.

“Feed wastage from a variety of feeder designs occurs most often as pigs back out of feeders, during fighting at the feeders and when pigs step into feeders in the case of feeders with large feeding areas relative to pig size. Large pigs waste less feed than small pigs, possibly due to less movement in and out of feeders during the eating process.”