Prediction of lamb carcass composition by impedance spectroscopy

Abstract

The objective of this study was to compare impedance spectroscopy with resistance measurements at a single frequency (50 kHz) for the prediction of lamb carcass composition. The impedance spectrum is usually recorded by measuring the complex impedance at various frequencies (frequency domain); however, in this study, we also applied the faster and simpler measurement in the time domain (application of a current step and measurement of the voltage response). The study was carried out on 24 male, German Black-headed Mutton lambs with an average BW of 45 kg. Frequency- and time domain-based impedance measurements were collected at 20 min and 24 h postmortem with different electrode placements. Real and imaginary parts at various frequencies were calculated from the locus diagram. Left sides were dissected into lean, fat, and bone, and right sides were ground to determine actual carcass composition. Crude fat, crude protein, and moisture were chemically analyzed on ground samples. Frequency- and time domain-based measurements did not provide the same absolute impedance values; however, the high correlations (P < 0.001) between these methods for the "real parts" showed that they ranked individuals in the same order. Most of the time domain data correlated higher to carcass composition than did the frequency domain data. The real parts of impedance showed correlations between -0.37 (P > 0.05) and -0.74 (P < 0.001) to water, crude fat, lean, and fatty tissue, whereas the relations to CP were much lower (from 0.00 to -0.47, P < 0.05). Electrode placements at different locations did not substantially improve the correlations with carcass composition. The "imaginary parts" of impedance were not suitable for the prediction of carcass composition. The highest accuracy (R2 = 0.66) was reached for the estimation of crude fat percentage by a regression equation with the time domain-based impedance measured at 24 h postmortem. Furthermore, there was not a clear superiority of measurements in a wide frequency range over a single frequency measurement at 50 kHz for the prediction of carcass composition. Even though we calculated the impedance at 50 kHz based on the locus diagram, which allowed for a high precision for predicting this impedance trait, single-frequency impedance devices typically used in practice cannot record the locus diagram and, therefore, exhibit a greater amount of uncertainty.

Relationship between plasma leptin concentrations and carcass composition in fattening mutton: a comparison with ultrasound results

“…perirenal, pelvic, omental and intestinal fat) were weighed and the left carcass half was dissected into lean, subcutaneous and intermuscular fat and bones. The chemical carcass composition was not analysed, because we previously have reported a high correlation ( r = 0.92) between the amount of dissected fatty tissues and the crude fat fraction of the carcass (Altmann et al., 2004).…”

In vivoEIS characterization of tumour tissue properties is dominated by excess extracellular fluid

“…the frequency at which the imposed current can travel with the same ease through the intracellular and the extracellular media (f p )), the tissue's relative permittivity at the peak frequency (ε rf p ) and the fluid index ratio (FIR). Electrical parameters have been shown to reflect the tissue's composition (Altmann et al 2004) as well as the tissue's microarchitecture (Brown et al 2000), changes which can be reflective of various diseases and malignant conditions. The non-destructive nature of this method makes EIS an attractive screening and/or diagnostic tool with which disease-associated changes may be monitored at regular intervals without pain or harmful consequences.…”