Group Size at Loading Is Insignificant

A study at the Prairie Swine Centre in Saskatchewan, Canada compared handling attributes, stress responses and meat quality of pigs from conventional and large group auto-sort pens marketed through the same facilities.

A total of 240 market hogs raised in conventional small groups (16-18 pigs/pen) or in large groups with auto-sort facilities (250 pigs/pen) were marketed over 10 days. Pigs were loaded in groups of four up a ramp onto a trailer. Transportation took 45 minutes to the packing plant and lairage was about four hours.

Behavioral and physiological measures were taken prior to, during and after the handling and transport process. Loins from the animals were assessed 24 hours after slaughter.

In general, it took 50% longer to load pigs from small groups. The need to use electric prods was similar for both groups (Table 1).

Differences observed in heat balance variables (temperatures, skin color and breathing) were early in the handling process, with an increase in rectal temperature after removal from the pen, and an increase in ear temperature once loaded on the trailer, for the pigs from the small group (Table 2).

Cortisol levels, reflective of acute stress, increased about three-fold from handling in the barn to after unloading at the plant, equally present in both large and small groups (Table 2).

Meat quality differences were evident between the two groups. Pigs from small groups had a higher degree of marbling and higher light reflectance (L*), but also a redder color (a*), shown in Table 3.

Other meat quality scores, such as pH, color and Japanese color, suggest there was slightly less response to stress in large group pigs.

Specific project funding was provided by the National Pork Board.

Researchers: S.M. Hayne, D.L. Whittington and H.W. Gonyou, all of the Prairie Swine Centre. Contact Ken Engele by phone (306) 373-9922, fax (306) 955-2510 or e-mail Ken.Engele@usask.ca.

Table 1. Assessment of Handling of Pigs from Large and Small Groups During the Loading Process

  Group Size
Large Small
Level of encouragement1 2.83 2.90
Number of shocks 8.30 12.03
Duration of loading, seconds 52.58 78.71
1Scores are 1 (board only); 2 (board, slap and yell); 3 (prod).

Table 2. Physiological Data of Pigs from Large and Small Groups During Various Stages of the Marketing Process

  Group Size
Prehandling (Barn) Truck Plant
Large Small Large Small Large Small
Ear Temp, F° 93.2 94.1 90.0 92.9 90.9 92.3
Rectal Temp, F° 102.6 103.1 104.0 104.2 39.1 102.4
Cortisol, nmol/L1 11.4 10.4 - - 31.8 27.1
Breathing Score2 1.0 1.02 1.08 1.1 1.07 1.04
Skin Score3 1.01 1.11 1.20 1.21 1.38 1.33
1Nmol/L refers to nanomoles/liter, which expresses the concentration of cortisol found in saliva.
2Breathing score (1-4) refers to 1 = no signs of heavy breathing; 2 = mouth open; 3 = rapid breathing; 4 = breathing sounds very raspy and labored.
3Skin score (1-4) refers to 1 = no signs of skin discoloration; 2 = skin is slightly pink; 3 = red and white areas visible on pig's skin; 4 = very distinct red and white blotches visible on pig's skin.

Table 3. Meat Quality Assessment of Pigs from Large and Small Groups

  Group Size
Large Small
pH 5.75 5.71
Texture1 3.36 3.25
Color2 3.43 3.24
Marbling3 2.51 2.71
L* (lightness) 51.8 53.4
a* (redness) 2.60 2.95
b* (yellowness) 10.25 10.18
Japanese color 3.45 3.36
Drip loss, % 9.74 9.88
1Texture rating 1: Pale, soft and exudative (PSE); 5: Dark, firm and dry (DFD).
2Color (1-6) 1: pale/gray white; 6: dark purplish red.
3Marbling (1-10) 1: absence of marbling; 10: heavy marbling.

Sow Behavior Cited in Most Crushing Losses

Variation in sow behavior may be more important than piglet behavior in trying to reduce crushing losses the first 72 hours of the piglet's life, according to a research study from Iowa and Texas animal scientists.

Preweaning piglet crushing losses cost an estimated $100 million/year.

Better understanding of the behavioral consequences that piglets and sows engage in prior to crushing may help develop system designs that enhance the well-being of the compromised piglet.

This study compared behavior (nursing) and postures (active and inactive) for piglets during the first 72 hours after farrowing when housed in an outdoor farrowing hut.

No differences were found in the behavioral activities of outdoor, loose-housed piglets that resulted in death by crushing in the first three days after birth. Therefore, researchers concluded, the sows' behavior is a more significant cause of piglet crushing than variation in piglet behaviors.

A plastic shed inside the central hub area of the farrowing pasture housed four, time-lapse video recorders to capture farrowing activities inside four farrowing huts.

Eight PIC Camborough-22 litters were used for behavioral comparisons for piglets in a litter where the dam killed a piglet or did not kill a piglet over the first 72 hours after farrowing.

Researchers: J.R. Garvey, A.K. Johnson, A.J. Holliday, L.J. Sadler and K.J. Stalder, all of Iowa State University, and J.J. McGlone of Texas Tech University. Contact Johnson by phone (515) 294-2098, fax (515) 294-4471 or e-mail johnsona@iastate.edu.

Maintaining Group Integrity Improves Sow Performance

In group-housed sows, when similar groups of sows are maintained throughout the gestation period, aggression between groups is reduced, and the culling rate is reduced due to non-productive parameters, increasing the sows' lifetime productivity.

Researchers at the Prairie Swine Centre in Saskatchewan, Canada studied aggression and injuries resulting from grouping sows after breeding.

Searching for methods to reduce aggression, sows were regrouped within a few days of breeding, using five experimental social groups.

Groups contained 16 bred sows. All animals had previous experience in group housing with an electronic sow feeder. Sows were regrouped at 11 days after breeding and placed in a mixing pen on 80 sq. ft. of partially slotted floor.

Each group consisted of approximately equal numbers of Parity 1-2 sows and Parity 3-6 sows. Less than 50% of all penmates within the respective groups were familiar, having shared a pen during the previous gestation.

The five treatment groups included:

  • Control: Group of sows formed as above;

  • Familiar: Sows from the same previous gestation group;

  • Dominant: Standard group of sows and three socially dominant animals that were large (Parity 5 or higher), housed together for at least six weeks, and well acquainted with the mixing pen;

  • Protected: Standard group of sows, but provided with seven free-access half-stalls to offer protection to head and shoulders; and

  • Exposed: Standard group of sows, except these sows were weaned directly into the mixing pen and held there for 48 hours before being moved to the breeding stall.

After regrouping, saliva samples and data on aggression and injuries were collected.

Scores for aggression and injuries among the five social management treatments are detailed in Table 1. The “familiar” treatment, where group integrity is maintained, appears to provide the best opportunity for reducing aggression. Researchers believe that the relatively short fights that occurred among familiar sows probably represented reinforcement of social position rather than the establishment of new hierarchy.

In the “dominant” group, the presence of three older animals from a well-established social order produced fewer aggressive events, particularly on the first day of group formation. The concept behind this treatment is that sows would avoid aggression when in the presence of a clearly dominant individual.

The “exposed” treatment, where sows had spent 48 hours together after weaning, but before being placed in stalls for breeding, did not reduce the incidence of aggression compared to the “control” group, except on the first day. But the level of injuries was reduced.

Researchers noted the short period of pre-exposure used in this study may have only provided a weak social order that required additional establishment after the subsequent regrouping.

This study confirmed other reports showing the ineffectiveness of protective stalling on the aggression among regrouped sows, as in the “protected” group.

No differences were observed in overall salivary cortisol concentrations — a measure of stress levels — among the five treatment groups (Table 1).

However, there were differences in cortisol levels on different days, with the lowest concentration prior to regrouping, and the highest levels on all the days following regrouping (Table 2).

In conclusion, maintaining sows in similar groups from gestation period to gestation period increases the odds of reduced aggression, compared to the other regrouping strategies tested.

But this method would not always be practical. Having dominant sows within the group tended to reduce aggression and injuries on the first day following regrouping. A similar trend was found when sows were exposed to each other before breeding. Protection during regrouping didn't prevent aggression or injuries.

Researchers: H.W. Gonyou and S.M. Hayne, both of the Prairie Swine Centre (PSC). Contact Ken Engele of the PSC by phone (306) 373-9922, fax (306) 955-2510 or e-mail ken.engele@usask.ca.

Table 1. Incidence of Aggression and Injuries Among Regrouped Sows on Five Social Management Treatments

  Treatments
Control Dominant Exposed Protected Familiar
Fighting (#/6 hrs)
Overall 6.4 4.3 6.9 13.9 5.7
1st day 11.4 5.8 8.6 17.5 10.8
2nd day 3.9 3.7 6.3 6.5 2.9
3rd day 3.7 3.9 5.8 17.7 3.5
Fighting (sec/6 hrs)
Overall 79 48 71 105 21
1st day 203 88 116 207 45
2nd day 17 37 63 55 11
3rd day 18 28 32 54 8
Injuries (score)1
Day 1-3 7.7 6.2 4.7 6.2 4.2
10 days 4.1 5.6 3.3 3.3 2.5
Cortisol (nmol/L)2
Overall 5.9 7.2 5.6 4.0 5.8
1Twelve regions of the body were scored as either 0 = no injury; 1 = slight injury (<5 superficial wounds); 2 = obvious injury (5-10 superficial wounds and/or < = 3 deep wounds); 3 = severe injury (>10 superficial wounds and/or >3 deep wounds). The total score was used in the analysis.
2Cortisol (nmol/L) nanomoles/litre: represents the concentration of cortisol (stress hormone) in saliva.

Table 2. Incidence of Aggression and Injuries Among Regrouped Sows on Five Social Management Treatments

  Day
  Pre 24 hr. 48 hr. 72 hr. 10 days
Cortisol (nmol/L)1 3.9 5.9 6.6 5.6 6.5
1Nanomoles/liter represents the concentrations of cortisol (stress hormone) in saliva.

Transport Space Allowances Studied for Weaned Pigs

Because the optimum space allowance required for weaned pigs during transport is unknown, Texas Tech University scientists sought to establish a first estimate of their space requirements based on measures of animal well-being.

A commercial livestock trailer was divided into compartments fitted for 100, 11.5-to-22-lb., weaned pigs at a space allowance of 0.5, 0.6 and 0.7 sq. ft./pig. Instruments recorded environmental conditions. Digital scans recorded the frequency of standing or lying behaviors of pigs every minute during the trip.

Prior to transport, blood samples were taken from four pigs per compartment for physiology and immune measures, and weight and lesion scores were recorded.

Pigs were then transported two hours to the wean-to-finish site using the same route for each of the four replications during winter.

At the finishing site, blood samples were again taken from the same experimental pigs.

Space allowance influenced the behavior of weaned pigs in the last 15 minutes of transport (Figure 1). Pigs transported at 0.6 sq. ft./pig spent less time standing than pigs transported at 0.5 and 0.7 sq. ft./pig.

Reduced standing behavior in pigs transported at 0.6 sq. ft./pig suggests that these pigs may have been in a more “relaxed” state during the last 15 minutes of transport, or became habituated to transport conditions sooner than pigs transported at 0.5 or 0.7 sq. ft./pig.

Researchers contend pigs appear to spend the majority of their time during transport active. However, pigs transported at 0.6 sq. ft./pig appear to spend more of their time resting than the other two treatment groups.

Cortisol concentrations and the neutrophil-to-lymphocyte ratio both increased during transport regardless of space allowance, trailer deck or gender (Table 1).

Increased cortisol concentrations and neutrophil-to-lymphocyte ratio in transported weaned pigs suggests these pigs experience stress, but the stress was not impacted by the space allowances tested.

Albumin concentrations were increased after transport, suggesting that these pigs were slightly dehydrated. Increased concentrations of create kinase and aspartate aminotransferase after transport suggest that these pigs were somewhat fatigued as a result of the two-hour transport. However, there was no effect of space allowance on any of these measures (Table 1).

No pigs died or were injured during the transport study. Body weight loss during transport did not differ among space allowances tested.

Researchers: M.A. Sutherland, N. Krebs, J.S. Smith and J.J. McGlone, all of the Pork Industry Institute, Texas Tech University. Contact Sutherland by phone (806) 742-2805 (ext. 253), fax (806) 742-4003 or e-mail mhairi.sutherland@ttu.edu.

Table 1. Blood Chemistry and Cortisol Concentrations of Weaned Pigs Before and After a Two-Hour Transport

  Time
  Before Transport After Transport
Number of animals 48 48
Neutrophil-to- Lymphocyte ratio 0.3 1.28
Cortisol, ng/mL1 40.7 62.7
Glucose, mg/dL2 128.5 125.0
Blood urea nitrogen, mg/dL3 8.5 9.8
Albumin, g/dL3 3.5 3.8
Aspartate aminotransferase, IU/L4 45.9 63.4
Creatine kinase, IU/L4 724.3 1,457.3
1Ng/mL = nanograms per milliliter
2Mg/dL = milligrams per deciliter
3g/dL = grams per deciliter
4IU/L = international units per liter

Alternate Tail Docking Procedure Cuts Stress

The use of the cautery iron rather than the conventional blunt trauma cutting method of tail docking can reduce the elevated stress response seen in newborn piglets without the use of analgesics or anesthetics.

Tail docking is routinely performed on piglets to prevent tail biting behavior.

Because analgesics and anesthetics are not routinely used to relieve the pain associated with tail docking on commercial hog farms, research was conducted to compare the stress response to tail docking using two methods: cautery iron (CAUT) and the more commonly used blunt trauma cutters (BT).

Six-day-old piglets' tails were docked using CAUT, BT or sham tail docked, where pigs were handled as if docking tails, but leaving their tails intact (CON). Blood samples were taken prior to tail docking and at 30, 60 and 90 minutes after tail docking to evaluate the effect of the procedure on cortisol concentrations, commonly used to assess stress levels (Figure 1, page 24). Piglet behavior was also recorded in the farrowing crate using one-minute scan samples via live observations for 60 minutes prior to and 90 minutes after tail docking.

Sixty minutes after tail docking, pigs tail docked using CAUT and CON had similar cortisol levels. Therefore, tail docking using cautery may reduce the acute stress response to tail docking.

Piglets tail docked using CAUT and BT spent more time posterior-scooting compared with CON piglets between 0 and 15 and 31 and 45 minutes after tail docking (Fiqure 2).

Elevated blood cortisol can be reduced with cautery iron rather than the BT method of tail docking. Although the tail docking-induced rise in cortisol was prevented by using CAUT, the behavioral responses to BT and CAUT docking methods were similar.

Researchers: M.A. Sutherland, P.J. Bryer, N. Krebs and J.J. McGlone, all of Texas Tech University. Contact Sutherland by phone (806) 742-2805 (ext. 253), fax (806) 742-4003 or e-mail Mhairi.sutherland@ttu.edu.

Waterer Bowl Location In Nursery Pens Tested

Pigs' preference for the location of drinker bowls was tested in a commercial nursery barn near Jefferson City, MO. Twenty-five, 7-week-old crossbred gilts were allocated to one of nine pens, configured with three treatment options:

Treatment 1 had one water bowl located on the same side of the pen as the feeder, close to the back wall (F).

Treatment 2 pens were equipped with two water bowl drinkers. One bowl was positioned as F (above), and the second was located across from the feeder along the back wall (O).

Treatment 3 had three water bowl drinkers/pen. Two were positioned as F and O, and the third bowl was located across from the feeder, but next to the alleyway (A).

Pigs preferred the drinker along the back wall (O), when given three choices (Figure 1). But when offered two water bowl drinker locations, they did not show a preference (F vs. O).

The least preferred location for a water bowl was next to the alleyway (A).

The number and length of aggressive interactions around the water bowl drinkers did not differ among treatment groups (Figure 2).

Researchers: C.J. Jackson, A.K. Johnson, L.J. Sadler, K.J. Stalder and L.A. Karriker, DVM, Iowa State University; R.E. Edler and J.T. Holck, Boehringer Ingelheim Vetmedica, Inc.; and P.R. DuBois, DVM, Cargill Pork. Contact Johnson by phone (515) 294-2098, fax (515) 294-4471 or e-mail johnsona@iastate.edu.