ENERGY-METABOLISM IN YOUNG-PIGS AS AFFECTED BY MIXING

The effect of mixing on energy metabolism was studied in 8-wk-old pigs . In each of two trials, two clusters of 20 pigs (two litters of 10 pi gs) were randomly assigned to one of two treatments: control or mixing . Each cluster was housed in one of two climatic chambers with each li tter in one of two pens. In each trial, after a preliminary period of 2 wk, the two litters within the mixing treatment were mixed at the st art of a 2-wk experimental period. During mixing, the five heaviest pi gs of each litter were put together in one pen, and the five lightest pigs of each litter were put together in the other pen. In the control treatment, the social structure of both litters in one climatic chamb er was not altered. After mixing, a short-term effect on total heat pr oduction and activity-related heat production was present. Both were i ncreased (P < .01) only during the Ist h after mixing. Only 57.3% of t his increased total heat production was caused by an increased activit y. However, no long-term effects of mixing on energy partitioning were present during the total experimental period. The absence of a long-t erm mixing effect might be caused by the optimal conditions at the mom ent of mixing. In the preliminary period the transposition of GE into ME increased 1.3% (P < .05), and ME for maintenance decreased 80 kJ . kg(-.75). d(-1) (P < .01) between wk 1 and 2. These large alterations in energy metabolism are probably a carry-over effect of the transport ation of the pigs and(or) the changes in housing environment.