Evaluating the application of dual X-ray energy absorptiometry to assess dissectible and chemical fat and muscle from the 9th-to-11th rib section of beef cattle
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2011 American Registry of Professional Animal Scientists. The objective of this study was to evaluate the adequacy of measuring dissectible fat and muscle from the 9th-to-11th rib section of beef cattle using a dual-energy X-ray absorptiometry (DEXA) scanner. Data were obtained from 52 9th-to-11th rib sections from steers, heifers, and bulls from 2 studies. The 9th-to-11th rib sections were removed from the carcasses, and digital images were obtained using the DEXA scanner. The outputs of the DEXA scanner were total fat percentage and lean muscle amount. The lean muscle percentage was calculated to compare with the rib dissection composition. The 9th-to-11th rib samples were physically dissected and chemically analyzed following standard procedures. Regression analyses were developed to evaluate the effect of sex on the predictability of the fat and muscle compositions using the DEXA values. The DEXA fat prediction explained 84 and 86% of the variation in the physical and chemical rib fats, respectively. For both predictions, the regression analysis indicated that the intercept and the slope were not different from zero and one (P < 0.001), respectively. The mean biases were significantly different from zero and underpredicted physical and chemical rib fats by 3.4 and 2.3%, respectively. The DEXA lean prediction explained 82 and 81% of the variation in the physically separable lean and chemical protein but overpredicted mean bias of -16 and -48%. These results indicate that DEXA scanners can precisely predict the 9th-to-11th rib section fat and lean tissue of beef cattle, but accuracy has to be improved.
