Can different loading levels of an automatic feeding system affect the Total Mixed Ration (TMR) physical homogeneity at distribution?

The aim of the study was to evaluate whether different loading levels of an automatic feeding system (AFS) could affect the physical homogeneity of the total mixed ration (TMR) at distribution. The field test was carried out on a beef farm in Northern Italy equipped with an AFS feeding approximately 350 Limousine cattle. The physical homogeneity of the TMR was assessed using the Penn State Particle Separator (PSPS) 2013 version. The animals were fed a TMR based on corn silage, corn mash, concentrates and distillers grains. Five AFS loading levels (10, 30, 50, 70 and 90% of the nominal bin volume) were tested. The physical homogeneity of the TMR distributed along the feeding alley was assessed by calculating the coefficient of variation (CV). As the ration consisted mainly of silage, the top sieve of the PSPS did not retain any forage particles. CVs lower than 5% were found in sieves 2 (middle), 3 (lower) and in the bottom pan for AFS loading levels ≥50% of the nominal bin volume, indicating that the ration was well homogenised. On the contrary, poorly mixed TMR (CV >5%) occurred along the feeding alley when the AFS bin was loaded to less than half the nominal volume, probably due to non-optimal mixing flows in the bin.