A comparison of pig backfat measurements using ultrasonic and optical instruments

Ultrasonic instruments have an important role in the prediction of backfat depth of live pigs, mainly for the purpose of selecting animals for leaner pork production. In order to achieve efficient lean pig production the accuracy of ultrasonic instruments in the prediction of backfat depth on live pigs and the correlations with values attained in the factory is therefore critical. Two commonly used hand-held ultrasonic devices, the SFK Pig Scan-A-Mode backfat scanner (SFK) and the Meritronics A-Mode Pulse Echo scanner (Meritronics), were evaluated using live pigs pre-slaughter and compared to measurements taken in the factory using the Ulster and Optical probes on the hot carcass, and after cutting of the chilled carcass using a digital calliper to measure backfat depth at the P2 position (65 mm from the dorsal mid-line at the level of the last rib). Instruments were used on a total of 120 pigs (60 boars and 60 gilts). The SFK was found to be a good predictor of the depth of backfat measured on the carcass at P2 in the factory using the Ulster and Optical probes. The Meritronics probe measured significantly (P < 0.001) lower depths of backfat at P2 (10.98 mm) than the Ulster and Optical probes (11.57 and 11.39 mm, respectively) and the SFK ultrasonic probe (11.67 mm). High correlations were established between all types of measurement with the relationships between the Ulster and Optical probes (r = 0.941) and the two ultrasonic probes (r = 0.924) being the greatest. Gilts were found to be significantly fatter (P < 0.01, average P2 difference = 1.2 mm) at a similar weight and age than boars. There was no significant interaction between the sex of the pig and outcome from the different probe types. In order to achieve effective genetic selection of leaner animals the SFK ultrasonic probe would be preferred for measurement of P2 on live pigs.