Animal Wellfare

Crowding Reduces Performance, Welfare Of Grow-Finish Pigs

Grow-finish pigs allocated more space, grew faster and exhibited better welfare characteristics and lower injury scores than groups in crowded conditions.

Both performance and welfare indicators were employed in a study at the University of Minnesota, funded by the Pork Checkoff. The study calculated the space allowance for grow-finish pigs using an allometric formula that weighs the size, shape and space utilization behavior of pigs.

Groups of 19 grow-finish barrows were evaluated at four levels of fully-slotted floor space: 6.9 sq. ft./pig, 8.0 sq. ft. /pig, 8.7 sq. ft./pig and 9.5 sq. ft./pig.

Pigs allocated 6.9 sq. ft./pig had lower average gain than those pigs allocated higher space allowances. The performance and welfare of the groups on higher space allowances were comparable in achieving a final slaughter weight of 256 lb. as depicted in Table 1.

Pen efficiencies (daily gain/unit of floor space) were similar across space allowance treatments during the final three weeks.

Grow-finish pigs were either sorted by size at placement or left in varying weight groups (Table 1). Sorting doesn’t appear to provide any benefits to average daily gain or overall welfare. But pigs in the varying weight groups spent more time lying in preferred areas than pigs in the uniform weight group.

Welfare of pigs appeared to be adversely affected at stocking densities of 6.9 sq. ft./pig, based on behavioral observations (increased aggression) and higher total injury levels. Salivary stress hormone levels did not differ with space allowance treatments.

Researchers: Leena Anil, DVM; Sukumarannair S. Anil, DVM; and John Deen, DVM, University of Minnesota. Contact Leena Anil by phone (612) 625-4243, fax (612) 625-1210 or e-mail .

Floor Space Plays Major Role in Hog Transport Losses

Many factors including genetics, health status, diet, handling intensity and facility design play a part in transport losses at the packing plant.

Increasing floor space during transport from 4.20 to 5.17 sq. ft./pig produced significant reductions in the incidence of total non-ambulatory pigs (0.62% vs. 0.27%); the incidence of non-ambulatory, non-injured pigs (0.52% vs. 0.15%); and the overall incidence of transport losses (0.88% vs. 0.36%).

That data is based on 74 loads of finishing pigs from wean-to-finish barns on two farms within one production system. Two different designs of straight, double-deck trailers were used for pig handling and transportation at 4.20 and 5.17 sq. ft./pig.

Variables measured in this study included the incidence of non-ambulatory pigs at the farm during loading and at the plant, average load weight, load number within each day, event times, and temperature and relative humidity in the trailer from loading to unloading.

Increasing floor space during transport greatly reduced the number of deads and non-ambulatory pigs at the plant. However, increasing floor space from 4.20 sq. ft./pig to 5.17 sq. ft./pig reduced numbers per load from 192 to 154, respectively.

“We also found that transport times and conditions may impact losses at the plant,” says Mike Ellis, professor of animal science, University of Illinois. “The incidence of non-ambulatory pigs at the farm increased as relative humidity during loading increased, and the number of trailers loaded by the same crew within a day increased.

“The overall incidence of transport losses at the plant increased as waiting and unloading time at the plant increased, and as the total transport time increased,” reports Ellis.

Average trailer temperature during transport and average pig weight on the trailer were unrelated to losses.

Researchers: M.J. Ritter, M. Ellis, J.M. DeDecker, M.E. Kocher, B.A. Peterson and J.M. Schlipf, University of Illinois; J. Brinkmann and B.F. Wolter, The Maschhoffs, Inc.; and K.K. Keffaber, DVM, Elanco Animal Health. Contact Ellis by phone (217) 333-6455, fax (217) 333-7861, or e-mail

Dynamic Group-Housed Sows Experience More Injuries, Aggression

Frequently mixed sows in group-housing systems featuring electronic sow feeders (ESF) incurred higher total injury scores (TIS) and compromised welfare vs. sows mixed twice or in static groups.

A Pork Checkoff-funded project at the University of Minnesota evaluated the effect of group size and structure on the welfare and production performance of gestating sows. In the study, three group-sow housing systems with ESF were established:

  • For the dynamic group, two adjacent pens of 50 sows were combined one month before the start of the experiment. The first batch of “experimental sows” was added to this 41.8 x 44.3-ft. combined pen with two ESF’s and six water bowls five days after breeding. At that time, another batch of sows in late gestation from the combined pen was moved to farrowing stalls.
    The next batch of sows was added 14 days later upon removal of another batch of sows in late gestation. This process was continued until the fourth batch of sows was added.
    The four batches of sows were kept together until the first batch of experimental sows was moved to farrowing stalls, and another new batch of sows was added to maintain group size. This process continued until all four batches were removed from the pen.
  • For the twice-mixed group, the first batch of weaned sows was mixed in 41.8 x 22.1-ft. pens five days after breeding, and the second batch was mixed 14 days later. A second, twice-mixed group was formed and similarly maintained.
  • One batch of a static group of sows was housed in one half of a 41.8 x 22-ft. pen, fed by a single ESF. Three other batches of sows were similarly penned.
    The results of the three groups of sows presented in Table 1 show no differences in terms of welfare indicators, such as cortisol concentrations, and the number of total aggressive interactions.
    But total injury scores were higher, and the number of non-aggressive interactions was lower in the dynamically group-housed sows, suggesting that the welfare of frequently mixed sows was compromised compared to the other groups.

Production performance was similar amongst all three group-housing situations.

Researchers: Leena Anil, DVM; Sukumarannair S. Anil, DVM; and John Deen, DVM, all of the University of Minnesota; and Samuel Baidoo and Roger Walker, Southern Research and Outreach Center, University of Minnesota-Waseca. Contact Leena Anil by phone (612) 625-4243, fax (612) 625-1210 or e-mail

Diet Changes Don’t Slow Stereotypic Behavior in Gestating Sows

Individual stall housing and feed restriction during gestation increase the incidence of stereotypic behavior by gestating sows. Activities include bar biting, sham chewing, and nosing or licking the floor or feeder when feed is not present.

Diets featuring 35% to 80% fibrous ingredients, particularly beet pulp, can greatly lower the incidence of stereotypic behavior during gestation. However, these high-fiber diets won’t flow through mechanical feeding systems.

Researchers at the University of Minnesota at Morris placed 239 second-parity and older sows on either a typical corn-soybean meal (control) diet at 4.7 lb./day, or a corn-soybean meal diet containing 40% soybean hulls fed at 5.7 lb./day. The higher feeding level for the fiber diet was necessary to compensate for the lower energy density of the fiber diet compared to the control diet.

Half of the control-fed sows and half of the fiber-fed sows were given their complete daily feed allotment at 7:30 a.m. (1X), while the other half were fed their daily feed allotment in two, equally-sized meals at 7:30 a.m. and at 2:30 p.m. (2X), throughout gestation.

On Days 40 and 80 of gestation, a subset of sows assigned to each feeding regimen was videotaped for 24 hours to observe the occurrence of stereotypic behavior (Figure 1). The taping confirmed that inclusion of 40% soybean hulls in a corn-soybean meal diet didn’t reduce the occurrence of stereotypic behaviors in gestating sows.

One reason for the development of stereotypic behavior is feed restriction imposed on sows that leaves them feeling hungry for long periods of time. High-fiber diets can provide sows with additional quantities of feed to offset hunger without gaining excessive condition.

But in this experiment, one additional pound of feed containing soy hulls was not enough to decrease stereotypic behavior. Another diet source with different fiber characteristics may be more effective. Feeding sows twice compared to once daily didn’t significantly impact the level of stereotypic behavior.

Researchers: Jonathon Holt and Lee Johnston, University of Minnesota-Morris; and Sam Baidoo and Jerry Shurson, University of Minnesota-St. Paul. Contact Johnston by phone (320) 589-1711, fax (320) 589-4870 or e-mail