Reducing stress can aid pig health, performance

Pigs can get stressed, just like people, and the impact can be just as serious. Stress is caused by any condition that forces a pig to adapt to changes in its normal environment, according to Dave Baumert, DVM, a technical service veterinarian for Zoetis.

Those conditions would include weaning, breeding, heat stress, crowding, shortages of feed or water — even social stress, he told Pig Health Today.

The negative impact of stress can be evident throughout the production cycle. When pigs have to adapt to something they’re not comfortable or familiar with, it can affect their immune system and increase risk for disease.

Stress affects immunity and health

When stress occurs, the pig’s response is to produce “a series of hormones and peptides within its system, the end result being the release of cortisone or cortisone-like products,” Baumert said.

Over the course of a few minutes, a pig that produces cortisone will attempt to overcome stress — and that’s good for the pig. But if this period of stress is prolonged for hours, days or weeks, the release of cortisone becomes a negative. This extended release of cortisone will decrease the effectiveness of white blood cells and impact the pig’s immune function, Baumert explained.

“Prolonged stress will decrease the number of antibodies a pig can produce, and in the case of pigs that are already ill or diseased, stressed pigs can actually release more disease organisms into the environment and infect their cohorts,” he said.

Stress in the production system

Some production practices, by their nature, create stress for pigs, like breeding, weaning, moving, transporting and mixing. Environmental factors play a role as well. (See Pig Health Today’s special
report on stress, published earlier this year.)

Stress on sows or gilts kept for breeding can have a negative effect on normal pig hormones like prostaglandin and progesterone — “the things that keep gilts cycling and sows pregnant,” Baumert said.

Weaning is the most likely time pigs will become stressed: They’re being moved and mixed, they’re put on a completely different diet, and they’re more likely to be susceptible to temperature changes.

Lack of feed, intermittent feed outages or diet changes can also create stress. Nutritional stressors on pigs can certainly produce ulcers in groups of pigs. Additionally, when pigs are loaded and transported to market they face additional stressors.

“Pigs face a stressful situation when they move from the farrowing [stall] to a wean-to-finish modern nursery, but they face a similar stress again when they move from the finishing stage to their final market or harvest plants,” Baumert said. He noted that about half a percent of the pigs marketed in the US each year arrive at the plant as downer pigs or fatigued pigs.

“There are a number of both short-term and long-term reasons for us, as caretakers of pigs, to reduce stress at every opportunity for the good of the pig,” he said.

Steps producers can take

The first step in dealing with pig stress is to recognize the kinds of stressors that can — and do — occur in a production system, including the ones listed above. The next step is to minimize those deterrents. For example, the industry’s move to weaning pigs at 23 to 28 days instead of 14 or 15 days helped minimize stress on both sows and pigs, and ultimately created higher profitability. 

“It is our opportunity and our obligation to reduce those stressors to the point where a pig can handle them, to where the pig can adapt without going through this cascade of negative biological effects,” Baumert said.

For example, moving day for young pigs needs to be a calm and quiet process, he said. “We need to move these small pigs in lots…and put them into a transport vehicle that is…properly vented and temperature controlled. The off-loading people need to take as much care with the pigs as the people who put the pigs on the vehicle in the first place.”

The same procedure should be followed with market animals. Baumert said market hogs should be loaded with as much patience and care as can be afforded “because, again, our goal is to take a quality product and present it to the market without having an undue number of downer or fatigued pigs arriving at the final destination.

“It really comes down to stepping outside of yourself and being more sensitive to the pigs’ needs,” he added. “It’s our job to recognize what could potentially stress a pig and then take steps to intervene for the pigs’ good.”