Influence of the addition of water to total mixed rations on the feeding behaviour, feed intake and milk performance of high-yielding dairy cows

The goal of this study was to investigate the influence of the addition of water to total mixed rations (TMR) with a dry matter (DM) content of 42 - 47% and high proportions of ensiled forage on feeding behaviour, DM intake (DMI) and milk performance, as well as changes in TMR temperature. The underlying hypothesis was a reduction in the selective feeding behaviour and a resulting increase in DMI of the cows, which were provided with a moist TMR. During two feeding trials, 48 German Holstein cows per trial were split into 2 groups (Trial I, winter: 85 +/- 28 d in milk (DIM); Trial II, summer: 67 +/- 34 DIM). Both trials were set up as a crossover design with period lengths of 45 (Trial I) and 35 (Trial II) d. The rations in each trial were made of the same components, had the same energy and nutrient concentrations and had slightly different DM contents. In Trial I, a TMR with 46.4% DM (dry TMR) was mixed with 12.5 kg water per cow per day, to reduce the DM content of the TMR to 37.3% DM (wet TMR). In Trial II, the DM content of 41.8% (dry TMR) was reduced to 33.9% (Wet TMR) after 14 kg of water per cow per day were added. The DMI of the individual animals and their milk yield were measured daily, and the milk composition was determined weekly. To judge the feeding behaviour, samples were taken from each feeding group at five points throughout the day during Trial I, and three during Trial II. The samples were tested for particle size distribution using a Penn State Particle Separator (PSPS). In both trials, the selective feeding behaviour was reduced as a consequence of the addition of water to TMR. In the case of the dry TMR, a change in particle size distribution in the troughs was already discernible 10 h after the feed was provided. In both trials, the addition of water had a positive influence on the DMI. In Trial I, the cows consumed 1.3 kg DM/d more as a consequence of the addition of water (p < 0.001), and in Trial II the difference equated to 0.6 kg DM/d after the addition of water (p < 0.001). The increased energy and nutrient intake of the cows that had been fed with the moistened TMR led to higher daily milk yield (Trial I: +0.6 kg/d; Trial II: +0.5 kg/d) and drinking water intake (p < 0.001). During the first 24 h after mixing the rations in Trial II (summer), no temperature differences were observed between the dry and moistened TMR. During the time period of 24-48 h after feeding, the dry TMR had an average temperature of 36.8 degrees C and the wet TMR had a temperature of 40.1 degrees C, which was a significant difference (p < 0.001). Furthermore, in Trial II, the increased energy and nutrient intake was reflected in a higher fat and protein yield and in an increased energy-corrected milk yield by 0.8 kg/d (p = 0.015). These results confirm that by adding water to TMR, selective feeding behaviour can be reduced and DMI increased, both during summer and winter trials. The importance of a uniform, non-selective feed intake in high-performing dairy cows is also evident from the results.