Effect of total mixed ration processing time on ration consistency and beef cattle performance during the early fattening period

The aim of this study was to assess the effect of processing time of the total mixed ration (TMR) on its physical and chemical characteristics, consistency over time, dry matter intake (DMI), rumination, activity, feed conversion ratio (FCR) and performance of beef cattle. The trial was conducted on 98 charolais bulls (476 +/- 36 kg) which were randomly assigned to two groups (1:54 animals in 6 pens; 2:44 animals in 5 pens). The two groups were fed rations with the same composition, but that were mixed for a short (20 min) mixing time (SMT) or for a 10 min longer mixing time (LMT). The trial lasted 60 days and was divided into 2 periods (P1 and P2). After P1 the diets were exchanged between groups according to a cross-over design. Animals were assessed for average daily weight gain (ADG), DMI, FCR, rumination and activity. All data were submitted to a mixed ANOVA model using the pen as random effect and period, mixing time and their interaction as fixed effects. The differences on TMR composition between pens and consecutive days within each diet, were tested through a GLM model using pen and day as fixed effects. A One-way ANOVA model was used to test the significance of the differences in activity and rumination between pens, within each diet, using the pen as fixed effect. The LMT ration had a lower particle geometric mean length (GML) compared with SMT (4.12 vs. 5.08 mm; P < 0.001). Bulls raised with the LMT showed a significantly higher ADG (1.96 vs. 1.87 kg/day; P = 0.035) and a lower conversion ratio (4.97 vs. 5.39; P = 0.036) compared with animals raised with SMT. Average daily rumination time and activity level did not differ between mixing time and were 381 min and 494 binary digits, respectively, but LMT bulls showed a lower (0.083 vs. 0.095; P = 0.012) index of dishomogeneity in activity (DA) and a lower sorting activity against long particles (99.8 vs. 96.3 %; P = 0.005). The variation of TMR composition between one day and another was significant (P < 0.001) for both neutral detergent fibre (aNDF) and starch in SMT, whereas in LMT it showed a tendency to significance (P = 0.056) only for neutral detergent fibre. These results indicate that LMT improved consistency of TMR over time, ADG, FCR and reduced feed sorting.