Evaluation of the non invasive tobec (total body electrical conductivity) procedure for prediction of chemical components of male broilers with special consideration of dietary protein level

Abstract

TOBEC (total body electrical conductivity) measurement as a non invasive procedure for the estimation of body chemical composition was used to calculate calibration curves for the prediction of crude protein mass (CPM), crude water mass (CWM), crude ash mass (CAM) and fat‐free mass (FFM) of male broiler chickens. A growth experiment with 3 protein levels (130, 230 and 330 g CP/kg diet, isoenergetic with 13.3 MJ AMEN/kg) was combined with TOBEC measurements and body chemical analysis in order to obtain the values necessary for calibration. A total of 196 TOBEC measurements and body chemical analysis were undertaken in time intervals of two days beginning with hatch until day 17 of age. Different dietary protein levels resulted in marked differences in body weights and body chemical compositions but in similar TOBEC‐responses for a given mass of FFM, CPM, CAM or CWM. Values for birds fed a diet with 130 g CP/kg diet tended to be more variable. Linear broken relationships were found between FFM, CPM, CAM and CWM, respectively, and TOBEC values (E#). A set of different regression equations is given and yielded high proportions of variance accounted for the piece wise regression model (R2 ranged from 0.83 to 0.99). In spite of these high determinations the prediction of crude fat mass (CFM) by subtracting the FFM from the body weight resulted in most cases in weak determinations between observed and predicted CFM (R2 ranged from 0.38 to 0.86). The highest R2 was observed when the E# was expressed per unit metabolic body weight to the power of 0.67 and regressed on FFM expressed to the same power. In conclusion, FFM, CPM and CWM may be predicted reasonably well by TOBEC. However, these high determinations are not high enough to predict CFM accurately. In addition, the application of such regressions to an individual bird seems to be impossible. Assessment for groups of animals should be possible if errors of estimation, standard deviations and differences to be detected are taken into account in the calculation of the number of birds necessary for the TOBEC measurements.