Introduction

There has been a move to increase the number of pigs penned together in finishing. Traditionally, pigs have been penned 20-40 pigs in a pen during the finishing phase. However over the last 10 years, an increasing number of producers have moved to grouping pigs in pens of 100 or more in finishing. Unfortunately there has been little direct comparative information on the performance, behavior or health differences when finishing pigs are penned in small versus large groups in finishing.

Large versus Small Pens

Recently a study from Saskatchewan, Canada^a, which utilized 2,304 pigs, compared those that that were penned in groups of either 18 (small group) or 108 (large group). In addition, pigs were either crowded (5.6 square feet per pig) or were uncrowded (8.4 square feet per pig) within each penning (small versus large) treatment.

Pigs were placed into finishing pens at approximately 83 lb and were approximately 207 lb at study completion. The same type wet/dry feeder was used in each penning treatment and feeder space allocation was nine pigs per space. All water was supplied through the wet/dry feeders. The data collected included body weight gain, along with injury scores, percentage of pigs needing medical treatment and pigs removed. In addition, the behaviour of eating, standing and sitting was also classified.

It was no surprise that pigs that were crowded grew slower than pigs that were uncrowded (2.27 versus 2.36 lb/day, respectively; Figure 1). What was unexpected were the results from the penning treatment comparison. Pigs that were penned in large groups grew slower than pigs in small groups (2.28 vs 2.37 lb/day, respectively; Figure 1).

Feed efficiency was also impacted by floor space allocation and group size (Figure 2). Pigs that were crowded had poorer feed efficiency than pigs that were not crowded (2.7 versus 2.5 lb feed/lb gain, respectively). As with average daily gain, pigs that were penned in large groups had poorer performance than pigs in small groups. Feed efficiency for pigs in large groups was 2.69 compared to pigs in small groups whose feed efficiency was 2.54. The interaction of floor space allocation and group size was not significant for either average daily gain or feed efficiency.

Penning treatment also influenced injuries. Pigs penned in large groups had more lameness and a greater severity of leg lesions compared to pigs penned in small groups. No difference was detected for flank and tail bites between the two penning treatments. Percentage of pigs receiving medical treatments was similar (7.4 per cent) across penning treatments as was removal percentage (3.65 per cent). Floor space allocation did not influence injuries nor medical treatment or removal percentage.

Pig behaviour was influenced by floor space allocation and penning treatment. The interaction of these two treatments was significant for percentage of the day spent eating and sitting (Table 1).

Pigs that were penned in small groups and were uncrowded spent the largest percentage of time eating while pigs penned in small groups and were crowded spent the least percentage of time eating. Pigs that were penned in large groups, regardless of floor space allocation were intermediate in percentage of time spent eating. Pigs penned in small, uncrowded groups spent the largest percentage of their day sitting while pigs in small, crowded groups were intermediate and pigs penned in large groups were lower in percentage of time sitting. Space allocation did impact the percentage of their time lying (Table 2). Pigs penned in large groups spent more time lying laterally (on their side) and less time lying ventrally (on their sternum) than pigs penned in small groups.

Conclusions

This study further confirmed that reduced floor space allocation or crowding in finishing reduces average daily gain. This study also demonstrated that crowding can result in poorer feed efficiency. Pigs that were penned in large groups of approximately 100 grew slower and had poorer feed efficiency than pigs penned in small groups of 18. At the conclusion of this study, pigs penned in the large groups were 7 lb lighter and consumed 8 more lb of feed per pig than pigs penned in small groups. This would result in both a reduction in sale weight and a higher feed cost per pig marketed.

Pigs penned in large groups also had a greater severity of lameness and leg lesions which is a welfare concern. However there were no differences in medical treatment or removal percentage, which suggests that group size does not influence morbidity.

Producers who are considering building new finishing facilities or renovating old barns should consider the ramifications of choosing large group versus small group penning. Large group penning may result in lower initial capital costs and possibly on-going repair costs. However, reductions in profitability due to slower growth and poorer feed conversion may overshadow any savings realized in lower equipment costs.

Literature Cited

^aStreet, B.R. and H.W. Gonyou. 2008. Effect of housing finishing pigs in two group sizes and at two floor space allocations on production, health, behavior, and physiological variables. J. Anim. Sci. 86:982-991.

January 2009