The different particle lengths of the grass silage were achieved by using different harvesting techniques (H = forage harvester, K = short-chop loader wagon, L = long-chop loader wagon). The dry matter content of the grass silage was increased from 35% (T35) to 50% (T50) by extending the wilting time in the field. The basic feed ration consisted of 60% grass silage and 40% corn silage and was supplemented with 25% (K25) or 55% (K55) concentrate. The study with rumen-fistulated cattle was conducted in the form of an incomplete Latin square over six trial periods of 14 days each. The experiment with dairy cows was carried out in two separate Latin squares (KF 25 and KF 55) with 12 animals each over six trial periods of 14 days each.
The mean particle length of the grass silage in groups H, K, and L was 38, 62, and 148 mm at low wilting (T35), and 32, 61, and 141 mm at high wilting (T50). Averaging both wilting levels, the mean particle length of the total ration in groups H, K, and L was 20, 31, and 69 mm with low concentrate supplementation (K25), and 13, 20, and 42 mm with high concentrate supplementation (K55).
In group T35, significant effects of the harvesting method on the digestibility of the organic matter (73.1, 71.3, 66.2) and the energy content (10.3, 10.1, 9.3 MJ ME) of the grass silage were observed. At a high wilting stage (T50), no effects of the harvesting method on the digestibility of the organic matter (71%) or the energy concentration (10.1 MJ NEL) were found. However, mold growth occurred during fermentation and/or storage in group T50. The affected feed portions could not be fed to animals.
In the study with fistulated cattle (Experiment 1), the harvesting method (H, K, L) had no effect on rumen fermentation, the digestibility of the total ration, or feed and nutrient intake. Significantly less grass silage was consumed in groups T50 than in T35. The pH value and the concentrations of volatile fatty acids and NH3 in the rumen fluid were not affected by the dry matter content of the grass silage. Increasing the concentrate feed proportion (K25 and K55, respectively) led to a reduction in forage intake from 9.0 to 6.6 kg D and an increase in total feed intake from 12.0 to 14.6 kg D. In K55, compared to K25, significantly lower digestibility of oxyfloc (67% and 60%, respectively) and non-ferrous fermentation fat (63% and 60%, respectively) was observed.
59%) and the ADF (63% and 59%, respectively) were observed. The mean daily pH of the rumen fluid in group K25 was 6.4, significantly higher than in group K55, where the mean was 6.2. The greatest differences in pH levels over the course of 30 days were observed approximately 4-7 hours after the start of feeding.
In the studies with dairy cows (Experiment 2), the harvesting method and the particle length of the grass silage also had no effect on feed and nutrient intake, nutrient supply, milk yield, or the cows' blood parameters. Increasing the dry matter content of the grass silage (T35 and T50) significantly reduced grass silage and forage intake. Forage intake was 12.5 kg dry matter (T35) and 11.3 kg dry matter (T50), respectively.
However, the animals in group T50 consumed more concentrate and corn silage than those in group T35. Increasing the concentrate intake (K25 and K55, respectively) led to a reduction in forage intake from 14.2 to 9.6 kg DM and an increase in total feed intake from 19.8 to 21.8 kg DM. No statistically significant differences in milk yield were observed between the concentrate intake levels (25.7 and 27.9 kg, respectively). The decrease in fat content from 4.77% to 4.24% was close to statistical significance.
No influence of grass silage particle length or harvesting technique on rumen fermentation, digestibility, or feed intake was observed. Extensive wilting of the grass silage resulted in poorer feed preservation and reduced forage intake.
Increasing the concentrate feed content led to a decrease in rumen pH and a reduction in the digestibility of structural carbohydrates. At a concentrate feed content of 55%, the ration was borderline in terms of structural and non-structural carbohydrate supply.
