Effect of mixing time of the total mixed ration on beef cattle performance

The aim of this study was to assess the effect of mixing time of the total mixed ration (TMR) on its physical and chemical characteristics, consistency over time, dry matter intake (DMI), rumination, activity and performance of beef cattle. The trial was conducted on 98 charolais bulls (476 ± 36 kg) which were randomly assigned to two groups (A: 54 animals in 6 pens; B: 44 animals in 5 pens) which were fed rations with the same composition (DM = 53.1; NDF = 33.0% DM; Starch = 32.6% DM; CP = 12.3% DM), but that were mixed for a standard mixing time (SMT) or for a 10 minutes longer mixing time (LMT). The trial lasted 60 days and was divided into 2 periods (P1 and P2). After P1 the diets were swop between groups according to a cross-over design. Animals were assessed for average daily weight gain (ADG), DMI, rumination and activity. Data on TMR, ADG, DMI, rumination and activity were submitted to a mixed model using the pen as random effect and period, mixing time and their interaction as fixed effects. The differences on TMR composition between consecutive days within each mixing time length were tested using a mixed model with the pen as random effect and the day of sampling as fixed effect. LMT ration, as expected, had a lower particle geometric mean length (GML) compared with SMT (4.12 vs. 5.08 mm). Bulls raised with the LMT showed a significantly higher ADG (1.96 vs. 1.87 kg/day; p < 0.05) and a lower conversion ratio (4.97 vs. 5.39; p < 0.05) compared with animals raised with SMT. Average daily rumination time and activity level did not differ between mixing time and were 381 minutes and 494 binary digits, respectively, but LMT bulls showed a lower (0.083 vs. 0.095; p < 0.05) index of dishomogeneity in activity (DA) and a lower sorting activity against long particles (99.8 vs. 96.3%; p = 0.005). SMT led to a more significant difference between consecutive days in NDF (p = 0.223 vs. p < 0.001) and starch content ( p = 0.077 vs. p < 0.001) of TMR than LMT. These results indicate that LMT improves consistency of TMR over time, ADG, conversion ratio and reduces feed sorting.