Review of group size effects on the performance of growing pigs.
2006
Payne, H. G. | Brumm, M. C. | DAntuono, M. | Pluske J. R. | Williams, I. H. | Moore, K. L. | Mullan, B. P.
Group size (number of pigs per pen) is an important factor in the design and management of facilities for growing pigs as it can influence capital requirement and the welfare and performance of pigs. Groups of 30 in commercial practice were previously considered as large, whereas today groups of 100-1000 pigs are used on some farms. This review examines early work, previous reviews of group size and recent work on the effect of group size on pig performance. The paper also incorporates an analysis of 19 recently published studies. The analysis showed that increasing group size from 5 to 100 pigs per pen appeared to have a small, negative effect on performance of weaner and finisher pigs provided that floor-space, and the number of feeders and drinkers was adequate. Group size appeared to have a greater impact on grower pigs, but this may be a reflection of the shorter duration of these particular studies. The review also describes a number of factors that may interact or be influenced by group size. These include carcass characteristics, behaviour, crowding, pen size and shape, and provision of resources such as feeders and drinkers. It can be concluded that pig behaviour alters with increasing group size and that much remains to be understood about pig behaviour in groups of 30-40 pigs and upwards. In practice, while housing pigs in large groups decreases construction, maintenance and cleaning costs, it may increase labour associated with inspection, treatment and marketing of pigs.
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