There is little available information on the influence of dietary energy on fat stores in the sow or on the relationship between these stores and backfat thickness measured at the P2 site. The present study was therefore designed to determine the influence of dietary energy intake in pregnancy on the fat stores of the sow after three parities including its relationship with P2 measurements taken at slaughter. In addition a comparison was made between ultrasonic measurement of P2 on the live animal and P2 measurements taken on the carcass.

There were three treatments with 15 sows per treatment which were rationed by live weight to receive approximately 30, 26, 23 MJ DE/day at 120 kg (Table 1). During lactation all sows were fed to a scale recommended by the ARC (1981) After weaning their third litter the sows were slaughtered and the left side of the carcass dissected into shoulder, ham, loin and belly joints as described by Fortin (1980). These were weighed, minced and analysed for fat content by the Folch method. P2 measurements were taken ultrasonically on the live animal, by probe on the hanging carcass and by straight measurement on the dissected loin.