An evaluation of ultrasound and nuclear magnetic resonance spectroscopy to measure in vivo intramuscular fat content of longissimus muscle of pigs

Intramuscular fat content (IMF) of longissimus muscle of pigs growing from approximately 20 to 100 kg was measured in vivo using biopsies after complete or localized anaesthesia, ultrasound and 1H nuclear magnetic resonance (NMR) technology. Three lines of pigs, with 60 animals each, were available. Biopsies were taken from the same pigs at 20, 60, and 100 kg, and fat was extracted for gravimetric determination. At 20 kg, ultrasound images were collected, and in vivo 1H NMR spectroscopy was applied. A-mode ultrasound measurements were collected at 60 and 100 kg. The overall mean value of IMF was 1.60 +/- .56% at 20 kg, 1.53 +/- .50% at 60 kg, and 1.71 +/- .60% at 100 kg. Interactions between lines and body weight were observed. No statistically significant differences were found between methods at 20 kg. No significant correlations were found between the A-mode ultrasound measurements and the mean values of the gravimetric measurements. No visible pain or infections were observed in relation to the collection of a single biopsy. The ultrasound method in combination with image analysis is advantageous from the labor point of view and will also improve welfare of pigs in case of repeated sampling. However, further research is necessary to make the technology sufficiently reliable. A correlation between IMF and backfat thickness was not found.