Autor: Stephanie Woida

Experimental studies on the effect of rations with different content of structurally effective raw fiber and the use of sodium hydrogen carbonate on the acid-base balance of dairy cows The feeding of high-yielding dairy cows often occurs at the interface between ensuring a demand-oriented energy supply and fulfilling a ruminant-oriented structural supply. This increasingly leads to feeding-related stress levels in the acid-base balance of the animals resulting in a negative impact on animal health. Over a period of 21 days respectively, four rumen-fistulous, lactating dairy cows were presented with a total of four different TMRs, which differed only in the chop length of the straw component used (straw meal, chop length approx. 0.2–0.5 cm; straw chop, chop length approx. 1–2 cm) and with regard to the addition of 120 g NaHCO3 per animal per day. During the 21-day study phases, rumen fluid, blood and urine samples were taken, and the feed intake was recorded in the time between feed presentation and sampling. Samples were taken daily during the first week and thereafter at intervals of three days. On days 3 and 21, additional daily examinations (5 a.m. to 5 p.m.) were conducted. The data of the monthly milk yield test was available as milk yield data. Within the test period, a shift of the acid-base balance in the acidotic direction was observed. No significant differences between the feeding groups were observed for feed intake and the parameters determined in blood and rumen fluid, except for the mean ruminal potassium concentration. In the urinary results, the groups without the addition of 120 g NaHCO3 per animal per day demonstrated an acidotic metabolic state with urinary parameters outside the reference ranges compared to the groups receiving NaHCO3 daily. The differences between the feeding groups were partly highly significant, depending on the use of NaHCO3. The rations used in this study have a negative effect on the acid-base balance of the animals, irrespective of the chop length of the straw components used. This could be mitigated by using 120 g NaHCO3 per animal per day. The results of the rumen fluid tests do not indicate any significant differences between the feeding groups. For the ration groups without the addition of NaHCO3, the diagnosis of subacute rumen acidosis in combination with the parameters of urine is correct (Staufenbiel 2011). In contrast, the ration groups with added NaHCO3 would tend to be classified as microbial rumen fermentation disorders.