The reproductive performance of the sow may be associated with the amount of fat stored in the body and the rate at which fat may be depleted. As body fat represents the easily mobilisable reserves of energy, an accurate and practical measurement of fat content is crucial. King et al (1986) have shown that linear baekfat measurements are the best single predictors of body fat compared to any other indirect indices of body composition. However practical experience has also suggested that fat measurements over the tuber coxae of the ileum (hip bone) will also provide an assessment of the fat status of a sow although its relationship to back fat depth is uncertain. Furthermore ultrasound techniques have not been tested in commercial conditions and the effectiveness of normal commercial practice in maintaining body fat reserves has not been previously examined.

The object of the investigation was to assess whether the fat status of the sow as determined by ultrasonic fat measurements at the P2 position (6.5 mm from the midline of the backbone at the last rib) and hip bone would give an objective assessment of the condition and performance of the sow. The effectiveness of normal commercial practice in maintaining herd condition was also assessed.