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.