METABOLIZABLE ENERGY OF MEAT AND BONE MEAL FROM SPANISH RENDERING PLANTS AS INFLUENCED BY LEVEL OF SUBSTITUTION AND METHOD OF DETERMINATION

Experiments were conducted to determine the ME(n) of eight meat and bone meal (MBM) samples. Samples averaged (DM basis): 6.01% moisture, 4.25 kcal gross energy (GE)/g, 53.3% CP, 14.5% ether extract (EE), 29.6% ash, 9.2% calcium, and 4.3% phosphorus. Samples of MBM were substituted in a corn basal diet at levels of 6, 12, 18, and 24%. Values of AME(n) were determined at each level of substitution and with regression analysis, because, in general, there were no significant deviations from linearity between dietary AME(n) and inclusion level. When considering all the samples studied, the average AME(n) values determined with substitution at the 6, 12, 18, and 24% levels of inclusion were 2.91, 2.76, 2.67, and 2.75 kcal/g, respectively, the differences not reaching significance (P > .05). The TME(n) values were determined by Sibbald's fasted cockerel method. Average values of MBM ME were similar whether determined by calculations based on substitution in the diet or by regression of the data (2.75 and 2.69 kcal/g, respectively). These values were similar to TME(n) obtained using Sibbald's method (2.74 kcal/g). Most of the differences in ME(n) among the samples studied could be attributed to differences in GE, although the percentage of GE metabolized [(ME + GE) x 100] tended to increase (R2 = .45; P = .069) when EE content in MBM increased. Gross energy was the best single predictor of both AME(n) and TME(n) (R2 = .88 and .76, respectively), but better estimations were achieved when using two independent variables in the prediction model: AME(n) = -910 + 44.8 (CP) + 83.6 (EE); R2 = .96, P < .001 and TME(n) = -491 + 34.4 (CP) + 96.5 (EE); R2 = .98, P < 001 (as DM basis).