The cellularity of adipose tissue from pigs of different weights

Abstract

Summary: Fat cell diameters were measured at 2-mm intervals throughout the depth of cores of subcutaneous shoulder and mid-back fat from ten Large White pigs. Five of the pigs were examined at 39 kg live weight and five at 70 kg live weight.In the shoulder fat of both groups there was a gradual change in fat cell size from the skin to the musculature. Cells were relatively small beneath the skin and adjacent to the underlying muscle and increased in size towards the junction of the inner and outer fat layers. The major difference between the two groups of pigs was that the cells closest to the skin and in the bulk of the inner layer were larger in the heavier animals whereas the cells at the junction of the two layers and closest to the muscle were similar in size. Such a uniform picture was not observed in the mid-back region where cells from the inner layer were larger than those from the outer layer.Cell size was Normally distributed at each site throughout the tissue. When the cell measurements for all the sites in each layer were combined there was no consistency in the type of distributions obtained although there was a tendency for them to be bimodal.In both layers of the shoulder fat there was a significant increase in the number of cells present in the 70 kg pigs compared with the 39 kg pigs and the new cells contributed considerably to the growth of the tissue between these weights. The observed cell size distributions and the cell size gradients within the tissue suggest that in the inner shoulder layer the new cells arise adjacent to the muscle. In the mid-back there was no significant difference in the number of fat cells present in the two groups of pigs and the growth of the mid-back fat was due to an increase in the size of fat cells already present.